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Rhus microphylla-mediated biosynthesis of copper oxide nanoparticles for enhanced antibacterial and antibiofilm efficacy

  • Nawal M. Al Musayeib , Musarat Amina EMAIL logo , Hanan M. Al-Yousef , Mohsin ul Haq , Sooad Al-Daihan and Ramesa Shafi Bhat EMAIL logo
Published/Copyright: November 18, 2024
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 13 Issue 1

Abstract

The global emergence and tenacity of multidrug-resistant microbes have raised new challenges for the management of diseases associated with infections. Metal-based nanoparticles (NPs) have recently received special attention as a prospective alternate for existing chemical antibiotics because of their extensive antibacterial potency and low toxicity. Herein, copper nanoparticles (CuONPs) were prepared by using an aqueous extract of aerial parts Rhus microphylla (RM) aerial parts. The obtained RM-CuONPs were characterized and evaluated for antimicrobial and antibiofilm potential against various human pathogens. The formed RM-CuONPs were well dispersed with a uniform spherical shape and an average size of 32.45 nm. Numerous functional moieties found in the FTIR spectra confirmed that the phytocomponents of the RM-extract were in charge of the synthesis synthesis, capping, and stabilization of RM-CuONPs. The biogenic RM-CuONPs demonstrated superior antibacterial effectiveness towards Staphylococcus epidermidis and Enterobacter cloacae with a minimum inhibitory concentration (MIC) value of 48.5 µg·mL−1. Remarkable antifungal activity of RM-CuONPs was noted against C. tropicalis (MIC = 97 µg·mL−1). Also, the biosynthesized RM-CuONPs demonstrated notable potential in reducing biofilm formation in a dose-dependent manner. These inferences offer an insight into the plausible for utilizing plant extracts for the biosynthesis of CuONPs with enhanced biological activity and could offer promising effective substitutes to traditional antimicrobials for the treatment of biofilms and drug-resistant bacteria.

Keywords: copper oxide nanoparticles; biosynthesis; antibacterial; antibiofilm; Rhus microphylla

1 Introduction

Nanomaterials have garnered more attention in recent times because of their prominent application in various domains, including materials science, medicine, biotechnology, and energetics [1]. Due to their size, distribution, and morphology, these nano-sized materials have novel and enhanced beneficial features which differentiate them from their counterpart bulk material [2]. As nanomaterials continue to be developed metal oxide nanoparticles (NPs) exhibit plenty of fascinating prospects in the biomedical field, particularly in the areas of antimicrobial and anticancer therapies, drug delivery, biosensing, and cell imaging [3]. Among these materials, copper oxide (CuO) NPs are considered a versatile candidate for biocompatible applications due to their biocompatibility, cost benefit, and low toxicity [4]. Their notable optical, structural, and biological properties, large surface area, chemical stability, enhanced stability-to-weight ratio, superior characteristics, and reusable nature render them suitable materials for industrial as well as biomedical applications [5]. Several conventional approaches, including biological, hydrothermal, solvothermal, and thermolysis of a few source precursor components, have been used to synthesize CuONPs [6]. All the physical procedures require high temperature and pressure, which rather are pretty pricey [7]. On the other hand, the use of chemical materials as reducers in chemical procedures has a negative effect on the environment and users, leading to several problems [8]. In contrast to these prior approaches, the green synthesis approach has lately introduced a facile and ecologically conscious route to synthesize them [9]. Biological resources, including; plant extracts, plants, bacteria, fungi, enzymes, and marine organisms are used in this process to create nanomaterials, and have several benefits for biomedical applications [10]. Out of all the natural resources, plants are favored over the others for the production of nanomaterials due to the presence of an array of phytochemicals, including flavonoids, glycosides, polyphenols, terpenoids, and enzymes, that function as reducing and capping agents for the synthesis of nanostructures with desired shape and size [11]. Plants are also preferred on competing biological techniques as they preclude the need for lengthy culturing times of microorganism as well as preservation [12]. Notably, plant extracts, inheriting therapeutic properties, can be utilized to obtain NPs with enhanced biological potential [13]. The current work exploits green methodology for the synthesis of CuONPs using a crude aqueous extract of R. microphylla (RM) and its anatomical components.

RM Engelm. ex A. Gray is a wild plant and a member of the family Anacardiaceae found in Central America, Mexico, and Southwestern United States [14]. It is a perennial shrub with branches that may grow up to 3 m tall. It has red fruits, glandular trichomes, and simple, evergreen leaves. The fruits of RM have locally been consumed as beverages and condiments by Kickapoo, the indigenous people of United States of America and Mexico [15]. The plant contains a plethora of phytoconstituents, including phenolic acids, flavonoids, betacyanins, betaxanthins, carbohydrates, and vitamins [16,17]. The fruits of this plant are a rich source of gallic acid, p-coumaric acid, +epicatechin, and ellagic acid [17]. Different extracts of RM have been reported for their antioxidant, antibacterial, and fungal activities [18].

Nanomaterials have been utilized extensively in medical applications due to their noteworthy and unique traits, such as quantum size effect, notably larger surface to mass ratio, adsorption capacity and ability to transfer materials like proteins, drugs, and probes, when compared to other particles [19].

Extensive research on antimicrobial resistance has demonstrated that pathogen that are resistant to antibiotics reside in biofilms, rather than as free bacteria [20]. Traditional antimicrobials are resistant to bacteria forming biofilm because (1) the inability of the antimicrobial to enter the biofilm, (2) development of intricate medication features and (3) alteration of antimicrobial enzymes by biofilms [21]. Interestingly, NP-based antimicrobials have been introduced and marketed to obliterate bacteria that are resistant to antibiotics and can form both planktonic and biofilm formation. Numerous studies have addressed the antibacterial potential of elemental Cu, CuO, and Cu2O, relating their morphology, particle size effect, and copper ion dissolution in different media [22,23,24]. Copper exhibits effective microbial inhibition by inflicting impairment to various functions of cells and exerting cytotoxicity [25]. The mechanism involves the generation of reactive oxygen species (ROS) and the replacement or native cofactors binding in metalloproteins. Additionally, copper plays a key role in intrinsic immunity, catalyzing ROS formation during phagocytosis and enhancing bactericidal activity [26]. The CuONPs employ similar mechanisms as displayed by other copper materials, with studies suggesting that metallic NPs possess stronger antimicrobial properties than their larger counterparts [27,28]. This heightened effectiveness is given credit for having a bigger surface area and unique crystal structure of CuONPs, influencing various cellular components in microbial cells through distinctive mechanisms [29,30]. The faster dissolution of CuONPs in solutions makes more metal ions available for release resulting in a more potent antimicrobial effect [31]. Furthermore, they are capable of concurrently activating diverse antibacterial pathways making it difficult for microorganisms acquire several gene alterations to resist these distinct antimicrobial actions [32]. Consequently, the likelihood of antimicrobial resistance is low. Biofilms represent intricate communities of microorganisms that exhibit resistance to antibiotics and the human immunological system, owing to their resilient and stable nature [33]. Eradicating biofilm infections poses a significant challenge, particularly in cases involving multidrug-resistant pathogens [34,35]. Both Gram-positive and Gram-negative bacteria are capable of forming biofilms and diseases linked to these biofilms are distinguished by persistent infections with slow development, showcasing the ability to withstand the immunological system of host and momentary reaction to antibiotic therapy [36]. Biofilms formed by some fungal strains of Candida inherently display resistance to traditional antifungal treatments as well as challenges from the host immune system, which pose a substantial clinical hurdle in managing infections [37]. Numerous reports have detailed the versatile potential of CuONPs as effective antimicrobial agents [38].

Owing to the massive significance of green and sustainable plant-mediated metal/metal oxide NP synthesis and promising antimicrobial profile of CuONPs, the aim of the current study was to utilize the copper ion reduction in synthesizing nano-sized materials using the RM plant extract. The present work described a facile, economical, environmentally benign, and green synthesis route of RM-CuONPs using readily accessible RM plants in Saudi Arabia. The aqueous extract of RM aerial parts enriched in phenolics and flavonoids served as reducers and stabilizers for the prospective utilization of the biogenic RM-CuONPs as antimicrobial agents. The novelty aspect of this study is that for the first time RM aerial parts were utilized for the formation of RM-CuONPs. The formed NPs were properly characterized by advanced analytical and microscopic techniques. In addition, the biosynthesized RM-CuONPs were explored for their antimicrobial and anti-biofilm activity against a panel of human pathogens. The prepared RM-CuONPs were also tested for their antioxidant potential by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay. The novel pre-synthesized RM-CuONPs can serve as an intriguing antimicrobial contender with promise for application in biomedicine.

2 Materials and methods

2.1 Chemicals

Copper(II) sulfate pentahydrate (CuSO4·5H2O, ≥98%), Mueller Hinton broth (MHB), dextrose agar, phosphate-buffered saline, and DPPH were used.

2.2 Biomass collection and preparation of extract

The aerial part of RM was obtained from rocky habitats of Madinah, Saudi Arabia, in April 2019. The collected botanical sample was recognized by a taxonomist Dr. M. Youseef, Pharmacognosy Department, King Saud University. The departmental herbarium now has a voucher specimen (RM-792) on file. The aerial parts of RM were washed with sterile distilled water to remove dust particles and then dried in the shade. The chopped dried plant material was mechanically processed into coarse powder with the help of a domestic blender. To prepare the extract of RM aerial parts, 10 g of powdered material was soaked in 500 mL of deionized water in a 500 mL beaker. After 1 h boiling, the mixture acquired the brown color in the colorless aqueous solution. The mixture was boiled for 1 h until the colorless aqueous solution changed to a brown color. The mixture was cooled, centrifuged for 5 min at 10,000 rmp and finally filtered over Whatman filter paper No.1 at room temperature to remove the biomaterials. The extraction process was conducted two more times under similar conditions. Finally, the obtained crude extract was stored was taken in air-tight glass bottles and kept cold (4°C) in fridge until needed.

2.3 Green synthesis of CuONPs

The biogenic CuONPs were synthesized by reducing copper sulfate with an aqueous extract of RM. Copper sulfate pentahydrate (CuSO4·5H2O) was utilized as the precursor for the synthesis of CuONPs. Briefly, 150 mL of copper sulfate (CuSO4·5H2O, 0.1 mM) was prepared in a 250 mL conical flask and then mixed with 25 mL of freshly prepared aqueous extract of RM aerial part under constant magnetic stirring at 60°C for 3 h. The change of light blue color of copper sulfate solution to a yellow color indicates the formation of copper hydroxide. The reaction mixture was then subjected to heating at 60°C under vigorous stirring until a color transition from dark yellow to dark brown was noticed, suggesting the formation of CuONPs. The fully reduced reaction mixture was centrifuged (5,000 rpm, 15 min) at ambient temperature, and the reaction mixture was collected after discarding the supernatant. The collected RM-CuONPs were oven dried at 80°C for 2 h, and after drying formed NPs were repeatedly rinsed with deionized water to free from all the impurities that were present. The dark brown RM-CuONP powder was obtained after overnight drying in an oven at 100°C and was ready for further characterization [39]. Figure 1 depicts the procedure of synthesizing CuONPs using an aqueous extract of aerial parts of RM extract and copper sulfate pentahydrate as a precursor.

Figure 1 Schematic representation of RM-CuONPs using an aqueous extract of RM aerial parts as a reducing agent and copper sulfate as a precursor.
Figure 1

Schematic representation of RM-CuONPs using an aqueous extract of RM aerial parts as a reducing agent and copper sulfate as a precursor.

The mechanism and the bioactive components responsible for the formation of NPs via plant extracts have not been entirely addressed yet [40]. The plausible mechanism of RM-CuONP formation, using the RM extract is outlined as follows:

(1) nCu 2 + → + 2 Ar – ( OH ) n → nCu 0 + 2 nAr = O  + 2 nH +

(2) 2 ( x + 1 ) Cu 0 + 2 Ar = O + y O 2 → 2 ( Cu 0 – Cu x O y – Ar = O )

The bioactive components such as phenolic and tannins (Ar–(OH) n ) of RM extract, responsible for the formation of CuONPs, could liberate their electrons for the efficient reduction of Cu2+ ions into Cu0. This might result in the formation of a Cu0–phenolate complex by the chelating effect causing the growth and nucleation of NPs at 60°C. The formed complex undergoes decomposition at a higher temperature (100°C) in air and leads to the generation of RM-CuONPs. Thus, the natural phenolics present in the RM extract had favorable effects on the biosynthesis of RM-CuONPs.

2.4 Characterization

The biosynthesized RM-CuONPs were characterized by measuring their absorption spectra in the 200–800 nm range on a double-beam UV–vis spectrophotometer (UV-2450, Shimadzu). Fourier transform infrared (FT-IR) analysis using KBr pellets in the 4,000–400 cm−1 range was implemented to identify the functional moieties involved in the precursor reduction into NPs (8400S spectrometer, Shimadzu). X-ray diffraction (XRD; 6000-XRD, Shimadzu) was performed at a scanning rate of 20°C·min−1 with 2θ in the 20°–80° range to obtain the structural information, crystallite size, and lattice constant of RM-CuONPs. The surface morphology of the formed RM-CuONPs was observed under scanning electron microscopy (SEM, JEOL JSM-6480, LV). A JEOL-2010 microscope running at 200 kV accelerating voltage was employed to record transmission electron micrographs (TEM). Energy-dispersive X-ray spectroscopy (EDS/EDX) coupled with SEM was applied to explore the atomic-level composition of the formed NPs. Zeta potential results were performed on a zeta potential/particle size analyzer (Brookhaven).

2.5 Antimicrobial and anti-biofilm activity

2.5.1 Microbial strains

The 13 clinical isolates used in this study were Gram-positive strains of Staphylococcus epidermidis, Enterococcus faecalis, Staphylococcus aureus, Streptococcus pneumoniae, and Bacillus subtilis; Gram-negative strains of Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Providencia stuartii, and Salmonella typhi; whereas, two fungal strains used were Candida albicans and Candida tropicalis. King Khalid Hospital in Riyadh provided all test strains. Before usage, all bacterial strains were reactivated on Mueller-Hinton agar (MHA) plates, and all fungal strains were reinstated on dextrose agar (SDA) plates respectively.

2.5.2 Antibacterial activity

The antibacterial effect was assessed by employing the well diffusion test. Every strain of bacteria had their overnight broth cultures adjusted to approximately 106 CFU·mL−1. About 20 µL was dispersed using a sterile cotton swab over 20 mL of sterilized agar plates. For around 3 min, the medium’s surface was allowed to dry. Sterile wells of 6 mm diameter were placed into the plates, and 100 L of test sample was put into every well to conduct the experiment. Following an incubation period of 24 h at 37°C, the diameter of the inhibitory zone (measured in mm) was applied to quantify the extent of microbial growth. Each test sample underwent three inspections, and the mean results are presented.

2.5.3 Determination of minimum inhibitory concentration (MIC)

MIC was determined by the broth micro-dilution procedure. In 96-well microtiter plates, the test solutions were serially diluted twice in MHB to reach the desired final concentrations ranging from 0. About 195–100 mg·mL−1 for the plant extract and from 0.097 to 50 mg·mL−1 for NPs. Then, each well was added with 100 mL of log-phase microbial culture adjusted to around 106 CFU·mL−1. The turbidity of media was observed for the bacterial growth after being incubated at 37°C for 16–18 hrs. The MIC was taken as the lowest concentration of extract or antibiotics necessary to limit microorganism growth without medium becoming turbid. Each assay was carried out three times.

2.5.4 Determination of minimum bactericidal concentration (MBC)

The test solutions in wells showing bacterial inhibition in the broth microdilution procedure mentioned above were laid on MHA and those showing fungal inhibitions were plated on dextrose agar and incubated at 37°C for 16–18 h. The MBC was taken as the most minimal extract or NPs concentration that was able to eradicate 99.9% of bacteria or fungi, displaying no growth on plates. Three duplicates of each assay were performed.

2.5.5 Determination of biofilm formation by the microtiter plate method

The influence of the extract and synthesized NPs on the biofilm establishment of the three most sensitive strains was tested through the microdilution method. Each microbial strain was nurtured in MHA for an entire night. After culture was diluted to 106 CFU·mL−1 it was put onto a 96-well microtiter plate containing two-fold serial dilutions of extract and NPs at 4MIC, 2MIC, MIC, 1/2MIC, and 1/4MIC. The control wells contained bacterial strains without extract and NPs, and there was just MHA in negative control wells. After incubation at 37° for 3 days, cells were dumped out by turning the plate over every well was rinsed with 200 μL of sterilized phosphate-buffered saline. Each well received 125 μL of 0.1% solution of crystal violet and incubated at ambient temperature for 15 min. Excess stains were rinsed away under running tap water. After letting the plates for air drying, 120 μL of glacial acetic acid (30%, v/v) was used to solubilize the stained biofilms. The amount of biofilm formed was quantified by measuring optical density (OD) at 570 nm, using an automatic micro ELISA plate. In qualitative assays, the wells were photographed.

2.6 Antioxidant activity

The ability of biosynthesized RM-CuONPs, aqueous RM extract, and standard L-ascorbic acid to scavenge the free radicals of DPPH at varied concentrations (5–140 µg·mL−1) was conducted by following the method of Schlesier et al. [41]. In brief, 2 mL of DPPH solution was poured into 0.1 mL of varying concentrations of each test sample and standard ascorbic acid and mixed well. After vigorous shaking for 1 min, the reaction mixture was given dark exposure for 30 min at ambient temperature and at 517 nm wavelength absorbance was noted with a UV-double beam spectrophotometer (UV-2900, Hitachi, Tokyo, Japan). Each assessment was performed in triplicate. The inhibition percentage of free radical (DPPH) was employed to indicate the capacity of each test sample to scavenge free radicals and was determined by applying the following equation:

Inhibition  ( % ) = A C − A S A C × 100

where sample and control absorbance was represented by A c and A s, respectively. The doses of the corresponding sample curve and the free radical scavenging ability relationship curve was used to obtain the IC50 values.

2.7 Statistical analysis

The results of antimicrobial activities were provided as the mean ± standard deviation (SD), and there were three replicates of each experiment.

3 Results and discussion

3.1 Synthesis and characterization of CuONPs

The green/biological synthesis approaches are currently far more effective than an array of physico-chemical procedures. The main reason for the effectiveness of these green/biological approaches lies in their ability to manipulate biological entities, including plants, fungi, bacteria, and algae, without the use of pricey hazardous chemicals and high energy intake [42]. The findings represented here utilize the extract of RM aerial parts as agents for surface capping, stabilization, and reduction in the biosynthesis of RM-CuONPs. The green synthesis of RM-CuONPs was assessed by the swift color change from yellowish to brown on account of the interaction between the precursor salt (CuSO4·5H2O) and the reducing agent under constant stirring. The UV–vis spectral estimation was conducted mainly to confirm the formation of biogenic RE-CuONPs. Figure 2a displays the spectra of RM extract and biogenic RM-CuONPs after UV–vis spectroscopic analysis in the 200 to 700 nm range. The UV–vis absorption spectrum of pre-synthesized RM-CuONPs demonstrated a pronounced absorption peak at 288 nm (Figure 2a), which is specific to CuONPs [43]. The surface plasmon resonance (SPR) of RM-CuONPs is responsible for this peak, and a broad SPR peak clearly demonstrates the polydispersity of the RM-CuONPs. These findings assure that phenolic and flavonoid contents in the RM extract successfully reduced the CuO precursor to form RM-CuONPs. The bandgap energy of the formed RE-CuONPs was measured by expanding the linear component graph and plotting energy (E g) versus (αhv)2, as illustrated in Figure 2a. The bandgap value of RE-CuONPs was calculated by applying the Tauc equation: α(hѵ)2 = A(hѵ – E g), where α, h, ѵ, A, and E g are the absorption coefficient, Planck’s constant, frequency, proportionality constant, and bandgap energy, respectively. The value of bandgap energy computed for RE-CuONPs was found to be 2.56, which coincides with the earlier documented energy bandgap estimations for CuO NPs [44]. A notable decrease in the bandgap energy could be attributed to bioactive components of the plants, which modify the surface and decrease the bandgap of formed NPs. Generally, green synthesized NPs are often more reactive than their conventionally produced counterparts [44].

Figure 2 (a) UV–vis spectrum and bandgap energy (inset) of biosynthesized RM-CuONPs. (b) XRD pattern of biosynthesized RM-CuONPs.
Figure 2

(a) UV–vis spectrum and bandgap energy (inset) of biosynthesized RM-CuONPs. (b) XRD pattern of biosynthesized RM-CuONPs.

The rapid synthesis of RM-CuONPs was strongly confirmed by XRD, and the X-ray diffractogram was used to estimate the particle size and various crystalline aspects of pre-synthesized RM-CuONPs. The XRD spectrum of biogenic RM-CuONPs revealed the existence of sharp distinct peaks at 2θ values of 32.30°, 35.42°, 38.92°, 48.65°, 57.13°, 61.59°, 66.41°, 68.23°, and 75.65° corresponding to (110), (−111), (111), (−202), (202), (113), (311), (202), and (222) lattice planes, respectively (Figure 2b). The resultant XRD pattern matched well with the JCPDS file no. 01-080-0076, indicating that the NPs were formed with a densely packed, monoclinic structure, which confirmed the crystalline nature and small crystallite size of the formed RM-CuONPs [45]. The formed RM-CuONPs were found to be in a monoclinic phase, as evidenced by the prominent peak in the (−111) direction. These results demonstrate that the crystalline form of CuONPs produced comparable types of peak indices as reported in the investigation that was conducted by Taghavi et al. [46].

The average crystallite sizes of the biogenic RM-CuONPs were obtained from XRD data in Figure 1b, using Debye–Scherrer’s formula. The computed values of crystallite size are listed in Table 1.

Table 1

Particle sizes of the biogenic Rm-CuONPs obtained from Figure 1b

No. of peaks Indices Location (2θ) FWHM (2θ) Size (nm) Strain (ε)
1 110 32.30 0.22611 52.21 0.22
2 −111 35.42 0.27247 50.26 0.26
3 111 38.92 0.29368 46.54 0.28
4 −202 48.65 0.34897 43.23 0.33
5 202 57.13 0.38719 42.46 0.36
6 113 61.59 0.43647 41.24 0.41
7 311 66.41 0.47198 38.84 0.45
8 202 68.23 0.48394 38.70 0.47
9 222 75.65 0.54328 28.39 0.51
Average size 42.43

The computed average crystallite size of pre-synthesized RM-CuONPs was 42.43 nm. The decrease in average crystallite size of RM-CuONPs was due to the influence of phyto-constituents that develop, control, and stabilize the formed crystals. However, the strain (ε) created in the NPs as a result of crystal distortion and imperfection was determined by applying the equation (ε = β cos θ/4), and Table 1 includes a list of values.

The lattice parameters refer to the values that characterize a unit cell or the periodicity unit of the atomic arrangement. The lattice constants (parameters) of a unit cell comprise three dimensional lengths (a, b, and c) with their mutual angles (α, β, and γ). They have been explored using the X-ray diffraction (XRD) method and are regarded as most important structural aspects that potentially impact physical features [47]. The lattice parameters for the monoclinic RM-CuONPs structure were obtained by applying the following equation

a = λ 3 sin θ   110

c = λ sin θ   − 111

The lattice parameters were computed, and the obtained results are presented in Table 2.

Table 2

Values of lattice parameters of biogenic CuO

NP 2θ (110) 2θ (−111) Lattice parameters
a = b c
RM-CuONPs 32.30 35.42 3.2450 5.090

The functional moieties of the obtained by stabilized RM-CuONPs from RM-extract were detected FTIR by the spectral band identifications. The spectra of biosynthesized RM-CuONPs and RM extract are shown in Figure 3. Different functional peak stretches are observed at 3,440.52, 2,910.32, 2,852.14, 2,367.59, 1,614.80, 1,426.72, 1,065.08, 619.86, and 432.12 cm−1 for RM-CuONPs and at 3,442.86, 2,914.46, 2,856.75, 2,389.46, 1,620.72, 1,432.52, 1,094.46, 620.23, and 587.21 cm−1 for the RM-extract in the FTIR spectrum. Two broad absorption bands appeared in the higher energy region at 3,440.52 and 3,442.86 cm−1 in the FTIR spectra due to the –OH stretching of phenolic and flavonoid constituents [48]. The existence of absorption bands at 2,910.32 and 2,914.46 cm−1 is indicative of –C–H stretching (hydroxyl compound). The peaks at 2,852.14 and 2,856.75 cm−1 represent the H–C–H group. While the peaks that appeared at 2,367.59 and 2,389.46 cm−1 are allocated to stretching vibrations of C═O or N–H group [49]. The peak positions at 1614.80 and 1620.72 cm−1 were indicative of the existence of either the bending C═N vibration in the amide group or the stretching C═O vibration in the carboxyl group respectively [50]. The COO symmetric stretching corresponds to the observed bands at 1,426.72 and 1,432.52 cm−1 [51]. The appearance of sharp intensity bands at 1,065.08 and 1,094.46 cm−1 were indicative of C–O bond stretching (aromatic rings) [52], which can also be associated with the flavonoid and phenolic compounds found in the RE-extract. The bands observed at 619.86 and 620.23 cm−1 revealed the occurrence of C–H bending outside of the plane. However, the FTIR spectrum of RM-CuONPs exhibited two distinct intense bands at 522.12 and 432.12 cm−1 were attributed to Cu–O and Cu–N stretching vibrations, respectively, suggesting the strong interaction between NPs and plant biomolecules [53]. Moreover, a decrease in the intensities bands of functional group after reduction of Cu2+ ions suggests the involvement of phenol and flavonoid sites in binding RM-CuONPs [54]. The phenolic components present in the RM-extract assisted in the conversion of copper sulfate to CuO and stabilized the formation of RM-CuONPs. The occurrence of different types of phytocomponents (phenol, flavonoids, steroids, tannins, and carbohydrates) in the RM-extract facilitates the formation of RM-CuONPs by serving as reducing and capping agents. The obtained results collectively provide evidence for the successful reduction of CuO to CuONPs. Our findings were consistent with those of previously published studies, addressing the characterization of green-synthesized CuONPs [55].

Figure 3 FTIR spectra of R. microphylla extract and biosynthesized RM-CuONPs.
Figure 3

FTIR spectra of R. microphylla extract and biosynthesized RM-CuONPs.

The surface morphology and size of the pre-synthesized RM-CuONPs were studied using SEM and transmission electron microscopy (TEM) techniques. While EDX analysis was employed to examine the content of elements and distribution. The high-resolution SEM image clearly reveals that the resulting RM-CuONPs have a uniform distribution and rounded in shape with certain degree of agglomeration (Figure 4a). The existence of phytoconstituents in the RM-extract is most likely the cause of aggregation in RM-CuONPs, due to the polarity and electrostatic interaction between the different particles of formed RM-CuONPs [56]. The nano size and spherical morphology of biosynthesized RM-CuONPs were further confirmed by the TEM visuals (Figure 4b), and the histogram for particle size distribution revealed a size range from 25.12 to 50.12 nm, with an average size of 32.45 nm (Figure 4c), which falls within the estimated range of the crystallite size found in the XRD analysis. A comparable size and shape of biosynthesized RM-CuONPs have been demonstrated in previous studies [57]. Furthermore, to get a deeper comprehension of the topographies of biogenic RM-CuONPs, the elemental composition and weight percentage of each element on the surface of formed NPs were estimated by EDX analysis. The elemental analysis validates the predominant presence of copper and oxygen in the formed nanostructure, indicating the high purity of the phyto-fabricated RM-CuONPs (Figure 4d). The weight and atomic percentage of copper (52.05 and 19.66%) and oxygen (32.42 and 49.02%) were determined, which and validated the formation of RM-CuONPs (Figure 4e). However, the appearance of a carbon signal in the EDX spectrum has been recognized as a consequence of residual organic plant extract contaminants (polyphenols, flavonoids, and proteins) on the NP or sample holder’s surface coated in carbon tape. Moreover, the results of RM-CuONPs mapping also supported the findings of EDX spectrum (Figure 4f–g). Mapping results also showed that the biosynthesized NPs contain phytoconstituents that were in charge of biological activities.

Figure 4 (a) SEM image, (b) TEM image, (c) particle size distribution histogram, (d) and (e) EDX spectrum, and (f)–(h) elemental mapping of biosynthesized RM-CuONPs from the RM extract.
Figure 4

(a) SEM image, (b) TEM image, (c) particle size distribution histogram, (d) and (e) EDX spectrum, and (f)–(h) elemental mapping of biosynthesized RM-CuONPs from the RM extract.

3.2 Antimicrobial activity

The antimicrobial efficacy of RM-extract and RM-CuONPs was assessed against various microbes, including S. epidermidis, E. faecalis, S. aureus, S. pneumoniae, B. subtilis, E. coli, E. cloacae, K. pneumoniae, P. aeruginosa, P. stuartii, S. typhi, C. albicans, and C. tropicalis. Figure 5 illustrates the antibacterial effect of RM-extract and RM-CuONPs by a well diffusion assay against diverse bacteria. The results indicate that RM-CuONPs exhibit remarkable antimicrobial activity against all the tested strains compared to the RM-extract. The degree of microorganism susceptibility is reflected in the size of the inhibitory zone. Notably, Gram-positive strains were more sensitive to RM-CuONPs than Gram-negative pathogens as indicated in Table 3. Compared to Gram-positive pathogens; the resistance of the Gram-negative bacteria to the RM-CuONPs was higher. The distinct structure of Gram-negative bacteria’s cell walls accounts for this variation. Gram-negative pathogens have an exterior coating of hydrophilic lipopolysaccharides that is considerably more resistant to the entry of antibacterial agents than the cell walls of Gram-positive bacteria. [37]. Furthermore, the degradation of antibiotic compounds is facilitated by the existence of enzymes in the periplasmic region of Gram-negative bacteria [58,59]. However, the fungal strains showed high sensitivity as compared to Gram-negative strains. As outlined in Table 3 and depicted in Figure 5, the RM-extract and RM-positive strains had inhibition zones measuring 20 ± 1.5 and 45 ± 1.0 mm, respectively, whereas best results among Gram-negative strains were shown towards E. cloacae with inhibition zones of 20 ± 1.0 and 45 ± 0.0 respectively. Similarly, RM-extract and RM-CuONPs exhibited the highest antifungal activity toward C. tropicalis with inhibition zones of 21 ± 10 mm and 45 ± 00 mm, respectively. Given that these three strains displayed the highest sensitivity to all tested strains, they were exposed to MIC and MBC. Table 4 depicts the values of MIC and MBC for both the RM-extract and RM-CuONPs.

Figure 5 Well diffusion assay demonstrating the antibacterial activity of 1 – RM-extract and 2 – RM-CuONPs against 13 different microbial strains.
Figure 5

Well diffusion assay demonstrating the antibacterial activity of 1 – RM-extract and 2 – RM-CuONPs against 13 different microbial strains.

Table 3

Zone of Inhibition (mm) of RM-extract and biosynthesized RM-CuONPs

Strains Zone of inhibition
RM-extract RM-CuONPs
Gram +ve S. epidermidis 20 ± 1.5 45 ± 1.0
E. faecalis 30 ± .1.2 40 ± 1.7
S. aureus 18 ± 1 45 ± 1.5
S. pneumoniae 20 ± 1.5 45 ± 2
B. subtilis 20 ± 1.0 40 ± 1.0
Gram –ve E. coli 15 ± 1.5 38 ± 1.0
E. cloacae 20 ± 1.0 45 ± 00
K. pneumoniae 15 ± 00 30 ± 1.0
P. aeruginosa 20 ± 1.0 40 ± 00
P. stuartii 25 ± 1.5 40 ± 1.0
S. typhi 20 ± .00 35 ± 1.0
Fungi C. albicans 20 ± 1.5 40 ± 1.00
C. tropicalis 21 ± 1.00 45 ± 00
Table 4

Values of MIC and MBC for the RM-extract and biosynthesized RM-CuONPs

Strains RM-extract RM-CuONPs
MIC mg·mL−1 MBC mg·mL−1 MIC μg·mL−1 MBC μg·mL−1
S. epidermidis 3.15 12.5 48.5 97
E. cloacae 6.25 25 48.5 97
C. tropicalis 25 50 97 190

Even though the specific antimicrobial mechanism of metal oxide nanomaterials is still not fully understood, it is commonly believed that their antimicrobial effects result from several factors: direct interaction with bacterial cell membranes, generation of ROS, and free metal ions release from the nanomaterials [60,61]. The toxicity of copper and CuO toward various microorganisms operates through multiple concurrent mechanisms, ultimately leading to the demise of the microorganisms. The initial target site of copper-induced damage appears to be the microorganism’s envelope [62]. The contact and breakdown of the pathogenic cell membrane, which permits the release of cytoplasmic components, is one of the hypothesized mechanisms underlying the antibacterial action [63]. The exposure of NPs can induce ROS generation, membrane permeability loss, cytoplasmic component leakage, and ultimately cell death [63]. The antibacterial action of CuNPs and CuONPs involves the destruction of cell membranes, ROS production, ribosomal instability, mitochondrial malfunction, lipid peroxidation, DNA degradation, and protein oxidation [64]. Copper ions inflict damage to nucleic acids following the copper binding specifically to DNA, and repeated cyclic redox reactions generate multiple hydroxyl radicals near the binding site, inflicting serious harm to nucleic acids (Figure 6). Nonetheless, it is plausible that, in certain pathogens, copper-induced oxidative disruption to genetic material could transpire via Fenton mechanism [65].

Figure 6 Schematic antibacterial mechanisms of CuONPs.
Figure 6

Schematic antibacterial mechanisms of CuONPs.

The effectiveness of RM-CuONPs in inhibiting the development of biofilm at sub-MIC doses was assessed towards S. epidermidis, E. cloacae, and C. tropicalis. As illustrated in Figure 7, the impact of RM-CuONPs on the biofilm formed by test strains demonstrated a concentration-dependent inhibition. In the range from 4MIC to 2 MIC of RM-CuONPs, the biofilm was almost completely eradicated. However, biofilm eradication also declined as the concentration lowered further. At 1/2 MIC, and 1/4 MIC, the biofilm was not entirely eradicated (Figure 7). The study on the anti-biofilm activity of RM-CuONPs demonstrated an efficient reduction in biofilm formation by test strains. The increase in NP concentration corresponded to enhanced biofilm inhibition, indicating a dose-dependent activity. Within 3 days of exposure to RM-CuONPs, nearly all test strain biofilm cells were observed to perish. The bacterial biofilm poses a persistent global health threat due to its high resistance to treatment and its capacity to worsen infections [33]. Consequently, identifying effective compounds to address this challenge is of utmost importance. In this research, we evaluated the efficacy of RM-CuONPs against the biofilms formed by various microbes. This study represents a pioneering effort to assess the anti-biofilm properties of RM-CuONPs. The ability of antibacterial agents to hinder the development or breakdown of biofilms presents a hopeful avenue for minimizing microbial colonization on surfaces and epithelial mucosa.

Figure 7 Microtiter plates demonstrating the anti-biofilm activity of RM-extract and RM-CuONPs.
Figure 7

Microtiter plates demonstrating the anti-biofilm activity of RM-extract and RM-CuONPs.

The antimicrobial activity of results of biosynthesized RM-CuONPs was compared with previously reported green-synthesized CuONPs and demonstrated in Table 5. The findings clearly indicated that the biogenic RM-CuONPs have exerted strong antibacterial and antifungal potential compared to earlier studies.

Table 5

Antibacterial properties of green-synthesized CuONPs using different plant extracts

Plant name Part used NP Antimicrobial activity MIC/MBC (μg·mL−1) Reference
Mangifera Indica Leaves CuONPs Antibacterial 120 [66]
Aegle marmelos Leaves CuONPs Antibacterial 125 [67]
Terminalia chebula Fruits CuONPs Antibacterial 250 [68]
Olea europaea Leaves CuONPs Antibacterial 250 [69]
Balanites aegyptiaca Stem bark CuONPs Antibacterial 100 [70]
Aerva javanica Leaves CuONPs Antibacterial, antifungal 128, 160 [39]
Cedrus deodara Leaves CuONPs Antibacterial 25 [71]
Catha edulis Leaves CuONPs Antibacterial 250 [72]
Ailanthus altissima Leaves CuONPs Antibacterial 20 [73]
Eupatorium odoratum Leaves CuONPs Antibacterial 100 [74]
Acanthospermum hispidum Leaves CuONPs Antibacterial 100 [74]

3.3 Antioxidant activity

The antioxidant properly of RM-CuONPs, aqueous RM-extract, and standard L-ascorbic acid is depicted in Figure 8. The obtained results showed that the DPPH scavenging potential of RM-CuONPs, aqueous RM-extract, and l-ascorbic acid at six varied doses (5–140 µg·mL−1) with the ranges being 10.68 to 76.12%, 24.02 to 87.90%, and 15.68 to 82.02%, respectively. The scavenging effect caused by RM-CuONPs was demonstrated by the DPPH assay findings, which showed an IC50 value of 29.12 ± 0.02 µg mL−1 for RM-CuONPs in comparison to 6.48 ± 0.01 µg mL−1 for RM-extract and 12.25 ± 0.04 µg mL−1 for reference ascorbic acid. Additionally, it was found that the RM-extract had enhanced potential for antioxidants than the reference L-ascorbic acid and RM-CuONPs, which might be due to occurrence of various bioactive components with increased phenolics and flavonoids content in the aqueous extract of RM plant.

Figure 8 DPPH free radical scavenging activity of RM-CuONPs, RM-extract, and ascorbic acid at different concentrations.
Figure 8

DPPH free radical scavenging activity of RM-CuONPs, RM-extract, and ascorbic acid at different concentrations.

4 Conclusions

The current research demonstrated the characterization, antimicrobial activity, anti-biofilm effect, and antioxidant prospective of green synthesized RM-CuONPs using an aqueous extract of RM. The characteristic features and quality of biogenic RM-CuONPs were examined by several sophisticated analytical techniques. The results of the investigation revealed that the RM plant extract efficiently reduced and stabilized the produced NPs. The outcome of the bio-fabricated approach yielded spherical and monoclinical structured RM-CuONPs with an average size of 32.45 nm. The FTIR analysis corroborated the formation of NPs with the appearance of broad absorption bands at 522.12 and 432.12 cm−1 for the RM-CuONPs. The formed biogenic RM-CuONPs showed remarkable antibacterial potential toward a panel of bacteria. RM-CuONPs exhibited considerable dose-dependent antibiofilm effects against S. epidermidis, E. cloacae, and C. tropicalis. These findings suggest that RM-CuONPs hold promise as effective antibiofilm agents against pathogenic microorganisms. Nonetheless, further investigation is required to ascertain their clinical efficacy and toxicity profile before considering clinical applications. Moreover, the biosynthesized RM-CuONPs have been observed to possess antioxidant potential with an IC50 value of 29.12 ± 0.02 µg·mL−1 toward the DPPH assay. In conclusion, the findings of this investigation validate the significance of RM-CuONPs mediated by RM extract as potential biological agents. These nanostructures offer a promising substitute for conventional medications in combating multi-drug-resistant pathogens. However, further studies are required to establish the biochemical processes and accountable mechanisms for the antibacterial and antioxidant activities.

Acknowledgements

This work was funded by the Researchers Supporting Project number (RSP2024R294), King Saud University, Riyadh, Saudi Arabia.

  1. Funding information: This research was funded by the Researchers Supporting Project number (RSP2024R294), King Saud University, Riyadh, Saudi Arabia.

  2. Author contributions: N.M.A.M.: conceptualization M.A. and H.M.A-Y.: formal analysis, M.H.: validation and figures, R.S.B.: biology methodology, writing – review and editing, visualization, data curation, S.A-D.: writing – review and editing. All authors have read and agreed to the published version of the manuscript.

  3. Conflict of interest: The authors state no conflict of interest.

  4. Data availability statement: All data generated or analyzed during this study are included in this published article.

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Received: 2024-05-06
Accepted: 2024-10-08
Published Online: 2024-11-18

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  16. Zinc oxide-manganese oxide/carboxymethyl cellulose-folic acid-sesamol hybrid nanomaterials: A molecularly targeted strategy for advanced triple-negative breast cancer therapy
  17. Exploring the antimicrobial potential of biogenically synthesized graphene oxide nanoparticles against targeted bacterial and fungal pathogens
  18. Biofabrication of silver nanoparticles using Uncaria tomentosa L.: Insight into characterization, antibacterial activities combined with antibiotics, and effect on Triticum aestivum germination
  19. Membrane distillation of synthetic urine for use in space structural habitat systems
  20. Investigation on mechanical properties of the green synthesis bamboo fiber/eggshell/coconut shell powder-based hybrid biocomposites under NaOH conditions
  21. Green synthesis of magnesium oxide nanoparticles using endophytic fungal strain to improve the growth, metabolic activities, yield traits, and phenolic compounds content of Nigella sativa L.
  22. Estimation of greenhouse gas emissions from rice and annual upland crops in Red River Delta of Vietnam using the denitrification–decomposition model
  23. Synthesis of humic acid with the obtaining of potassium humate based on coal waste from the Lenger deposit, Kazakhstan
  24. Ascorbic acid-mediated selenium nanoparticles as potential antihyperuricemic, antioxidant, anticoagulant, and thrombolytic agents
  25. Green synthesis of silver nanoparticles using Illicium verum extract: Optimization and characterization for biomedical applications
  26. Antibacterial and dynamical behaviour of silicon nanoparticles influenced sustainable waste flax fibre-reinforced epoxy composite for biomedical application
  27. Optimising coagulation/flocculation using response surface methodology and application of floc in biofertilisation
  28. Green synthesis and multifaceted characterization of iron oxide nanoparticles derived from Senna bicapsularis for enhanced in vitro and in vivo biological investigation
  29. Potent antibacterial nanocomposites from okra mucilage/chitosan/silver nanoparticles for multidrug-resistant Salmonella Typhimurium eradication
  30. Trachyspermum copticum aqueous seed extract-derived silver nanoparticles: Exploration of their structural characterization and comparative antibacterial performance against gram-positive and gram-negative bacteria
  31. Microwave-assisted ultrafine silver nanoparticle synthesis using Mitragyna speciosa for antimalarial applications
  32. Green synthesis and characterisation of spherical structure Ag/Fe2O3/TiO2 nanocomposite using acacia in the presence of neem and tulsi oils
  33. Green quantitative methods for linagliptin and empagliflozin in dosage forms
  34. Enhancement efficacy of omeprazole by conjugation with silver nanoparticles as a urease inhibitor
  35. Residual, sequential extraction, and ecological risk assessment of some metals in ash from municipal solid waste incineration, Vietnam
  36. Green synthesis of ZnO nanoparticles using the mangosteen (Garcinia mangostana L.) leaf extract: Comparative preliminary in vitro antibacterial study
  37. Simultaneous determination of lesinurad and febuxostat in commercial fixed-dose combinations using a greener normal-phase HPTLC method
  38. A greener RP-HPLC method for quaternary estimation of caffeine, paracetamol, levocetirizine, and phenylephrine acquiring AQbD with stability studies
  39. Optimization of biomass durian peel as a heterogeneous catalyst in biodiesel production using microwave irradiation
  40. Thermal treatment impact on the evolution of active phases in layered double hydroxide-based ZnCr photocatalysts: Photodegradation and antibacterial performance
  41. Preparation of silymarin-loaded zein polysaccharide core–shell nanostructures and evaluation of their biological potentials
  42. Preparation and characterization of composite-modified PA6 fiber for spectral heating and heat storage applications
  43. Preparation and electrocatalytic oxygen evolution of bimetallic phosphates (NiFe)2P/NF
  44. Rod-shaped Mo(vi) trichalcogenide–Mo(vi) oxide decorated on poly(1-H pyrrole) as a promising nanocomposite photoelectrode for green hydrogen generation from sewage water with high efficiency
  45. Green synthesis and studies on citrus medica leaf extract-mediated Au–ZnO nanocomposites: A sustainable approach for efficient photocatalytic degradation of rhodamine B dye in aqueous media
  46. Cellulosic materials for the removal of ciprofloxacin from aqueous environments
  47. The analytical assessment of metal contamination in industrial soils of Saudi Arabia using the inductively coupled plasma technology
  48. The effect of modified oily sludge on the slurry ability and combustion performance of coal water slurry
  49. Eggshell waste transformation to calcium chloride anhydride as food-grade additive and eggshell membranes as enzyme immobilization carrier
  50. Synthesis of EPAN and applications in the encapsulation of potassium humate
  51. Biosynthesis and characterization of silver nanoparticles from Cedrela toona leaf extracts: An exploration into their antibacterial, anticancer, and antioxidant potential
  52. Enhancing mechanical and rheological properties of HDPE films through annealing for eco-friendly agricultural applications
  53. Immobilisation of catalase purified from mushroom (Hydnum repandum) onto glutaraldehyde-activated chitosan and characterisation: Its application for the removal of hydrogen peroxide from artificial wastewater
  54. Sodium titanium oxide/zinc oxide (STO/ZnO) photocomposites for efficient dye degradation applications
  55. Effect of ex situ, eco-friendly ZnONPs incorporating green synthesised Moringa oleifera leaf extract in enhancing biochemical and molecular aspects of Vicia faba L. under salt stress
  56. Biosynthesis and characterization of selenium and silver nanoparticles using Trichoderma viride filtrate and their impact on Culex pipiens
  57. Photocatalytic degradation of organic dyes and biological potentials of biogenic zinc oxide nanoparticles synthesized using the polar extract of Cyperus scariosus R.Br. (Cyperaceae)
  58. Assessment of antiproliferative activity of green-synthesized nickel oxide nanoparticles against glioblastoma cells using Terminalia chebula
  59. Chlorine-free synthesis of phosphinic derivatives by change in the P-function
  60. Anticancer, antioxidant, and antimicrobial activities of nanoemulsions based on water-in-olive oil and loaded on biogenic silver nanoparticles
  61. Study and mechanism of formation of phosphorus production waste in Kazakhstan
  62. Synthesis and stabilization of anatase form of biomimetic TiO2 nanoparticles for enhancing anti-tumor potential
  63. Microwave-supported one-pot reaction for the synthesis of 5-alkyl/arylidene-2-(morpholin/thiomorpholin-4-yl)-1,3-thiazol-4(5H)-one derivatives over MgO solid base
  64. Screening the phytochemicals in Perilla leaves and phytosynthesis of bioactive silver nanoparticles for potential antioxidant and wound-healing application
  65. Graphene oxide/chitosan/manganese/folic acid-brucine functionalized nanocomposites show anticancer activity against liver cancer cells
  66. Nature of serpentinite interactions with low-concentration sulfuric acid solutions
  67. Multi-objective statistical optimisation utilising response surface methodology to predict engine performance using biofuels from waste plastic oil in CRDi engines
  68. Microwave-assisted extraction of acetosolv lignin from sugarcane bagasse and electrospinning of lignin/PEO nanofibres for carbon fibre production
  69. Biosynthesis, characterization, and investigation of cytotoxic activities of selenium nanoparticles utilizing Limosilactobacillus fermentum
  70. Highly photocatalytic materials based on the decoration of poly(O-chloroaniline) with molybdenum trichalcogenide oxide for green hydrogen generation from Red Sea water
  71. Highly efficient oil–water separation using superhydrophobic cellulose aerogels derived from corn straw
  72. Beta-cyclodextrin–Phyllanthus emblica emulsion for zinc oxide nanoparticles: Characteristics and photocatalysis
  73. Assessment of antimicrobial activity and methyl orange dye removal by Klebsiella pneumoniae-mediated silver nanoparticles
  74. Influential eradication of resistant Salmonella Typhimurium using bioactive nanocomposites from chitosan and radish seed-synthesized nanoselenium
  75. Antimicrobial activities and neuroprotective potential for Alzheimer’s disease of pure, Mn, Co, and Al-doped ZnO ultra-small nanoparticles
  76. Green synthesis of silver nanoparticles from Bauhinia variegata and their biological applications
  77. Synthesis and optimization of long-chain fatty acids via the oxidation of long-chain fatty alcohols
  78. Eminent Red Sea water hydrogen generation via a Pb(ii)-iodide/poly(1H-pyrrole) nanocomposite photocathode
  79. Green synthesis and effective genistein production by fungal β-glucosidase immobilized on Al2O3 nanocrystals synthesized in Cajanus cajan L. (Millsp.) leaf extracts
  80. Green stability-indicating RP-HPTLC technique for determining croconazole hydrochloride
  81. Green synthesis of La2O3–LaPO4 nanocomposites using Charybdis natator for DNA binding, cytotoxic, catalytic, and luminescence applications
  82. Eco-friendly drugs induce cellular changes in colistin-resistant bacteria
  83. Tangerine fruit peel extract mediated biogenic synthesized silver nanoparticles and their potential antimicrobial, antioxidant, and cytotoxic assessments
  84. Green synthesis on performance characteristics of a direct injection diesel engine using sandbox seed oil
  85. A highly sensitive β-AKBA-Ag-based fluorescent “turn off” chemosensor for rapid detection of abamectin in tomatoes
  86. Green synthesis and physical characterization of zinc oxide nanoparticles (ZnO NPs) derived from the methanol extract of Euphorbia dracunculoides Lam. (Euphorbiaceae) with enhanced biosafe applications
  87. Detection of morphine and data processing using surface plasmon resonance imaging sensor
  88. Effects of nanoparticles on the anaerobic digestion properties of sulfamethoxazole-containing chicken manure and analysis of bio-enzymes
  89. Bromic acid-thiourea synergistic leaching of sulfide gold ore
  90. Green chemistry approach to synthesize titanium dioxide nanoparticles using Fagonia Cretica extract, novel strategy for developing antimicrobial and antidiabetic therapies
  91. Green synthesis and effective utilization of biogenic Al2O3-nanocoupled fungal lipase in the resolution of active homochiral 2-octanol and its immobilization via aluminium oxide nanoparticles
  92. Eco-friendly RP-HPLC approach for simultaneously estimating the promising combination of pentoxifylline and simvastatin in therapeutic potential for breast cancer: Appraisal of greenness, whiteness, and Box–Behnken design
  93. Use of a humidity adsorbent derived from cockleshell waste in Thai fried fish crackers (Keropok)
  94. One-pot green synthesis, biological evaluation, and in silico study of pyrazole derivatives obtained from chalcones
  95. Bio-sorption of methylene blue and production of biofuel by brown alga Cystoseira sp. collected from Neom region, Kingdom of Saudi Arabia
  96. Synthesis of motexafin gadolinium: A promising radiosensitizer and imaging agent for cancer therapy
  97. The impact of varying sizes of silver nanoparticles on the induction of cellular damage in Klebsiella pneumoniae involving diverse mechanisms
  98. Microwave-assisted green synthesis, characterization, and in vitro antibacterial activity of NiO nanoparticles obtained from lemon peel extract
  99. Rhus microphylla-mediated biosynthesis of copper oxide nanoparticles for enhanced antibacterial and antibiofilm efficacy
  100. Harnessing trichalcogenide–molybdenum(vi) sulfide and molybdenum(vi) oxide within poly(1-amino-2-mercaptobenzene) frameworks as a photocathode for sustainable green hydrogen production from seawater without sacrificial agents
  101. Magnetically recyclable Fe3O4@SiO2 supported phosphonium ionic liquids for efficient and sustainable transformation of CO2 into oxazolidinones
  102. A comparative study of Fagonia arabica fabricated silver sulfide nanoparticles (Ag2S) and silver nanoparticles (AgNPs) with distinct antimicrobial, anticancer, and antioxidant properties
  103. Visible light photocatalytic degradation and biological activities of Aegle marmelos-mediated cerium oxide nanoparticles
  104. Physical intrinsic characteristics of spheroidal particles in coal gasification fine slag
  105. Exploring the effect of tea dust magnetic biochar on agricultural crops grown in polycyclic aromatic hydrocarbon contaminated soil
  106. Crosslinked chitosan-modified ultrafiltration membranes for efficient surface water treatment and enhanced anti-fouling performances
  107. Study on adsorption characteristics of biochars and their modified biochars for removal of organic dyes from aqueous solution
  108. Zein polymer nanocarrier for Ocimum basilicum var. purpurascens extract: Potential biomedical use
  109. Green synthesis, characterization, and in vitro and in vivo biological screening of iron oxide nanoparticles (Fe3O4) generated with hydroalcoholic extract of aerial parts of Euphorbia milii
  110. Novel microwave-based green approach for the synthesis of dual-loaded cyclodextrin nanosponges: Characterization, pharmacodynamics, and pharmacokinetics evaluation
  111. Bi2O3–BiOCl/poly-m-methyl aniline nanocomposite thin film for broad-spectrum light-sensing
  112. Green synthesis and characterization of CuO/ZnO nanocomposite using Musa acuminata leaf extract for cytotoxic studies on colorectal cancer cells (HCC2998)
  113. Review Articles
  114. Materials-based drug delivery approaches: Recent advances and future perspectives
  115. A review of thermal treatment for bamboo and its composites
  116. An overview of the role of nanoherbicides in tackling challenges of weed management in wheat: A novel approach
  117. An updated review on carbon nanomaterials: Types, synthesis, functionalization and applications, degradation and toxicity
  118. Special Issue: Emerging green nanomaterials for sustainable waste management and biomedical applications
  119. Green synthesis of silver nanoparticles using mature-pseudostem extracts of Alpinia nigra and their bioactivities
  120. Special Issue: New insights into nanopythotechnology: current trends and future prospects
  121. Green synthesis of FeO nanoparticles from coffee and its application for antibacterial, antifungal, and anti-oxidation activity
  122. Dye degradation activity of biogenically synthesized Cu/Fe/Ag trimetallic nanoparticles
  123. Special Issue: Composites and green composites
  124. Recent trends and advancements in the utilization of green composites and polymeric nanocarriers for enhancing food quality and sustainable processing
  125. Retraction
  126. Retraction of “Biosynthesis and characterization of silver nanoparticles from Cedrela toona leaf extracts: An exploration into their antibacterial, anticancer, and antioxidant potential”
  127. Retraction of “Photocatalytic degradation of organic dyes and biological potentials of biogenic zinc oxide nanoparticles synthesized using the polar extract of Cyperus scariosus R.Br. (Cyperaceae)”
  128. Retraction to “Green synthesis on performance characteristics of a direct injection diesel engine using sandbox seed oil”
https://doi.org/10.1515/gps-2024-0102
Keywords for this article
copper oxide nanoparticles; biosynthesis; antibacterial; antibiofilm; Rhus microphylla
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Green polymer electrolyte and activated charcoal-based supercapacitor for energy harvesting application: Electrochemical characteristics
  3. Research on the adsorption of Co2+ ions using halloysite clay and the ability to recover them by electrodeposition method
  4. Simultaneous estimation of ibuprofen, caffeine, and paracetamol in commercial products using a green reverse-phase HPTLC method
  5. Isolation, screening and optimization of alkaliphilic cellulolytic fungi for production of cellulase
  6. Functionalized gold nanoparticles coated with bacterial alginate and their antibacterial and anticancer activities
  7. Comparative analysis of bio-based amino acid surfactants obtained via Diels–Alder reaction of cyclic anhydrides
  8. Biosynthesis of silver nanoparticles on yellow phosphorus slag and its application in organic coatings
  9. Exploring antioxidant potential and phenolic compound extraction from Vitis vinifera L. using ultrasound-assisted extraction
  10. Manganese and copper-coated nickel oxide nanoparticles synthesized from Carica papaya leaf extract induce antimicrobial activity and breast cancer cell death by triggering mitochondrial caspases and p53
  11. Insight into heating method and Mozafari method as green processing techniques for the synthesis of micro- and nano-drug carriers
  12. Silicotungstic acid supported on Bi-based MOF-derived metal oxide for photodegradation of organic dyes
  13. Synthesis and characterization of capsaicin nanoparticles: An attempt to enhance its bioavailability and pharmacological actions
  14. Synthesis of Lawsonia inermis-encased silver–copper bimetallic nanoparticles with antioxidant, antibacterial, and cytotoxic activity
  15. Facile, polyherbal drug-mediated green synthesis of CuO nanoparticles and their potent biological applications
  16. Zinc oxide-manganese oxide/carboxymethyl cellulose-folic acid-sesamol hybrid nanomaterials: A molecularly targeted strategy for advanced triple-negative breast cancer therapy
  17. Exploring the antimicrobial potential of biogenically synthesized graphene oxide nanoparticles against targeted bacterial and fungal pathogens
  18. Biofabrication of silver nanoparticles using Uncaria tomentosa L.: Insight into characterization, antibacterial activities combined with antibiotics, and effect on Triticum aestivum germination
  19. Membrane distillation of synthetic urine for use in space structural habitat systems
  20. Investigation on mechanical properties of the green synthesis bamboo fiber/eggshell/coconut shell powder-based hybrid biocomposites under NaOH conditions
  21. Green synthesis of magnesium oxide nanoparticles using endophytic fungal strain to improve the growth, metabolic activities, yield traits, and phenolic compounds content of Nigella sativa L.
  22. Estimation of greenhouse gas emissions from rice and annual upland crops in Red River Delta of Vietnam using the denitrification–decomposition model
  23. Synthesis of humic acid with the obtaining of potassium humate based on coal waste from the Lenger deposit, Kazakhstan
  24. Ascorbic acid-mediated selenium nanoparticles as potential antihyperuricemic, antioxidant, anticoagulant, and thrombolytic agents
  25. Green synthesis of silver nanoparticles using Illicium verum extract: Optimization and characterization for biomedical applications
  26. Antibacterial and dynamical behaviour of silicon nanoparticles influenced sustainable waste flax fibre-reinforced epoxy composite for biomedical application
  27. Optimising coagulation/flocculation using response surface methodology and application of floc in biofertilisation
  28. Green synthesis and multifaceted characterization of iron oxide nanoparticles derived from Senna bicapsularis for enhanced in vitro and in vivo biological investigation
  29. Potent antibacterial nanocomposites from okra mucilage/chitosan/silver nanoparticles for multidrug-resistant Salmonella Typhimurium eradication
  30. Trachyspermum copticum aqueous seed extract-derived silver nanoparticles: Exploration of their structural characterization and comparative antibacterial performance against gram-positive and gram-negative bacteria
  31. Microwave-assisted ultrafine silver nanoparticle synthesis using Mitragyna speciosa for antimalarial applications
  32. Green synthesis and characterisation of spherical structure Ag/Fe2O3/TiO2 nanocomposite using acacia in the presence of neem and tulsi oils
  33. Green quantitative methods for linagliptin and empagliflozin in dosage forms
  34. Enhancement efficacy of omeprazole by conjugation with silver nanoparticles as a urease inhibitor
  35. Residual, sequential extraction, and ecological risk assessment of some metals in ash from municipal solid waste incineration, Vietnam
  36. Green synthesis of ZnO nanoparticles using the mangosteen (Garcinia mangostana L.) leaf extract: Comparative preliminary in vitro antibacterial study
  37. Simultaneous determination of lesinurad and febuxostat in commercial fixed-dose combinations using a greener normal-phase HPTLC method
  38. A greener RP-HPLC method for quaternary estimation of caffeine, paracetamol, levocetirizine, and phenylephrine acquiring AQbD with stability studies
  39. Optimization of biomass durian peel as a heterogeneous catalyst in biodiesel production using microwave irradiation
  40. Thermal treatment impact on the evolution of active phases in layered double hydroxide-based ZnCr photocatalysts: Photodegradation and antibacterial performance
  41. Preparation of silymarin-loaded zein polysaccharide core–shell nanostructures and evaluation of their biological potentials
  42. Preparation and characterization of composite-modified PA6 fiber for spectral heating and heat storage applications
  43. Preparation and electrocatalytic oxygen evolution of bimetallic phosphates (NiFe)2P/NF
  44. Rod-shaped Mo(vi) trichalcogenide–Mo(vi) oxide decorated on poly(1-H pyrrole) as a promising nanocomposite photoelectrode for green hydrogen generation from sewage water with high efficiency
  45. Green synthesis and studies on citrus medica leaf extract-mediated Au–ZnO nanocomposites: A sustainable approach for efficient photocatalytic degradation of rhodamine B dye in aqueous media
  46. Cellulosic materials for the removal of ciprofloxacin from aqueous environments
  47. The analytical assessment of metal contamination in industrial soils of Saudi Arabia using the inductively coupled plasma technology
  48. The effect of modified oily sludge on the slurry ability and combustion performance of coal water slurry
  49. Eggshell waste transformation to calcium chloride anhydride as food-grade additive and eggshell membranes as enzyme immobilization carrier
  50. Synthesis of EPAN and applications in the encapsulation of potassium humate
  51. Biosynthesis and characterization of silver nanoparticles from Cedrela toona leaf extracts: An exploration into their antibacterial, anticancer, and antioxidant potential
  52. Enhancing mechanical and rheological properties of HDPE films through annealing for eco-friendly agricultural applications
  53. Immobilisation of catalase purified from mushroom (Hydnum repandum) onto glutaraldehyde-activated chitosan and characterisation: Its application for the removal of hydrogen peroxide from artificial wastewater
  54. Sodium titanium oxide/zinc oxide (STO/ZnO) photocomposites for efficient dye degradation applications
  55. Effect of ex situ, eco-friendly ZnONPs incorporating green synthesised Moringa oleifera leaf extract in enhancing biochemical and molecular aspects of Vicia faba L. under salt stress
  56. Biosynthesis and characterization of selenium and silver nanoparticles using Trichoderma viride filtrate and their impact on Culex pipiens
  57. Photocatalytic degradation of organic dyes and biological potentials of biogenic zinc oxide nanoparticles synthesized using the polar extract of Cyperus scariosus R.Br. (Cyperaceae)
  58. Assessment of antiproliferative activity of green-synthesized nickel oxide nanoparticles against glioblastoma cells using Terminalia chebula
  59. Chlorine-free synthesis of phosphinic derivatives by change in the P-function
  60. Anticancer, antioxidant, and antimicrobial activities of nanoemulsions based on water-in-olive oil and loaded on biogenic silver nanoparticles
  61. Study and mechanism of formation of phosphorus production waste in Kazakhstan
  62. Synthesis and stabilization of anatase form of biomimetic TiO2 nanoparticles for enhancing anti-tumor potential
  63. Microwave-supported one-pot reaction for the synthesis of 5-alkyl/arylidene-2-(morpholin/thiomorpholin-4-yl)-1,3-thiazol-4(5H)-one derivatives over MgO solid base
  64. Screening the phytochemicals in Perilla leaves and phytosynthesis of bioactive silver nanoparticles for potential antioxidant and wound-healing application
  65. Graphene oxide/chitosan/manganese/folic acid-brucine functionalized nanocomposites show anticancer activity against liver cancer cells
  66. Nature of serpentinite interactions with low-concentration sulfuric acid solutions
  67. Multi-objective statistical optimisation utilising response surface methodology to predict engine performance using biofuels from waste plastic oil in CRDi engines
  68. Microwave-assisted extraction of acetosolv lignin from sugarcane bagasse and electrospinning of lignin/PEO nanofibres for carbon fibre production
  69. Biosynthesis, characterization, and investigation of cytotoxic activities of selenium nanoparticles utilizing Limosilactobacillus fermentum
  70. Highly photocatalytic materials based on the decoration of poly(O-chloroaniline) with molybdenum trichalcogenide oxide for green hydrogen generation from Red Sea water
  71. Highly efficient oil–water separation using superhydrophobic cellulose aerogels derived from corn straw
  72. Beta-cyclodextrin–Phyllanthus emblica emulsion for zinc oxide nanoparticles: Characteristics and photocatalysis
  73. Assessment of antimicrobial activity and methyl orange dye removal by Klebsiella pneumoniae-mediated silver nanoparticles
  74. Influential eradication of resistant Salmonella Typhimurium using bioactive nanocomposites from chitosan and radish seed-synthesized nanoselenium
  75. Antimicrobial activities and neuroprotective potential for Alzheimer’s disease of pure, Mn, Co, and Al-doped ZnO ultra-small nanoparticles
  76. Green synthesis of silver nanoparticles from Bauhinia variegata and their biological applications
  77. Synthesis and optimization of long-chain fatty acids via the oxidation of long-chain fatty alcohols
  78. Eminent Red Sea water hydrogen generation via a Pb(ii)-iodide/poly(1H-pyrrole) nanocomposite photocathode
  79. Green synthesis and effective genistein production by fungal β-glucosidase immobilized on Al2O3 nanocrystals synthesized in Cajanus cajan L. (Millsp.) leaf extracts
  80. Green stability-indicating RP-HPTLC technique for determining croconazole hydrochloride
  81. Green synthesis of La2O3–LaPO4 nanocomposites using Charybdis natator for DNA binding, cytotoxic, catalytic, and luminescence applications
  82. Eco-friendly drugs induce cellular changes in colistin-resistant bacteria
  83. Tangerine fruit peel extract mediated biogenic synthesized silver nanoparticles and their potential antimicrobial, antioxidant, and cytotoxic assessments
  84. Green synthesis on performance characteristics of a direct injection diesel engine using sandbox seed oil
  85. A highly sensitive β-AKBA-Ag-based fluorescent “turn off” chemosensor for rapid detection of abamectin in tomatoes
  86. Green synthesis and physical characterization of zinc oxide nanoparticles (ZnO NPs) derived from the methanol extract of Euphorbia dracunculoides Lam. (Euphorbiaceae) with enhanced biosafe applications
  87. Detection of morphine and data processing using surface plasmon resonance imaging sensor
  88. Effects of nanoparticles on the anaerobic digestion properties of sulfamethoxazole-containing chicken manure and analysis of bio-enzymes
  89. Bromic acid-thiourea synergistic leaching of sulfide gold ore
  90. Green chemistry approach to synthesize titanium dioxide nanoparticles using Fagonia Cretica extract, novel strategy for developing antimicrobial and antidiabetic therapies
  91. Green synthesis and effective utilization of biogenic Al2O3-nanocoupled fungal lipase in the resolution of active homochiral 2-octanol and its immobilization via aluminium oxide nanoparticles
  92. Eco-friendly RP-HPLC approach for simultaneously estimating the promising combination of pentoxifylline and simvastatin in therapeutic potential for breast cancer: Appraisal of greenness, whiteness, and Box–Behnken design
  93. Use of a humidity adsorbent derived from cockleshell waste in Thai fried fish crackers (Keropok)
  94. One-pot green synthesis, biological evaluation, and in silico study of pyrazole derivatives obtained from chalcones
  95. Bio-sorption of methylene blue and production of biofuel by brown alga Cystoseira sp. collected from Neom region, Kingdom of Saudi Arabia
  96. Synthesis of motexafin gadolinium: A promising radiosensitizer and imaging agent for cancer therapy
  97. The impact of varying sizes of silver nanoparticles on the induction of cellular damage in Klebsiella pneumoniae involving diverse mechanisms
  98. Microwave-assisted green synthesis, characterization, and in vitro antibacterial activity of NiO nanoparticles obtained from lemon peel extract
  99. Rhus microphylla-mediated biosynthesis of copper oxide nanoparticles for enhanced antibacterial and antibiofilm efficacy
  100. Harnessing trichalcogenide–molybdenum(vi) sulfide and molybdenum(vi) oxide within poly(1-amino-2-mercaptobenzene) frameworks as a photocathode for sustainable green hydrogen production from seawater without sacrificial agents
  101. Magnetically recyclable Fe3O4@SiO2 supported phosphonium ionic liquids for efficient and sustainable transformation of CO2 into oxazolidinones
  102. A comparative study of Fagonia arabica fabricated silver sulfide nanoparticles (Ag2S) and silver nanoparticles (AgNPs) with distinct antimicrobial, anticancer, and antioxidant properties
  103. Visible light photocatalytic degradation and biological activities of Aegle marmelos-mediated cerium oxide nanoparticles
  104. Physical intrinsic characteristics of spheroidal particles in coal gasification fine slag
  105. Exploring the effect of tea dust magnetic biochar on agricultural crops grown in polycyclic aromatic hydrocarbon contaminated soil
  106. Crosslinked chitosan-modified ultrafiltration membranes for efficient surface water treatment and enhanced anti-fouling performances
  107. Study on adsorption characteristics of biochars and their modified biochars for removal of organic dyes from aqueous solution
  108. Zein polymer nanocarrier for Ocimum basilicum var. purpurascens extract: Potential biomedical use
  109. Green synthesis, characterization, and in vitro and in vivo biological screening of iron oxide nanoparticles (Fe3O4) generated with hydroalcoholic extract of aerial parts of Euphorbia milii
  110. Novel microwave-based green approach for the synthesis of dual-loaded cyclodextrin nanosponges: Characterization, pharmacodynamics, and pharmacokinetics evaluation
  111. Bi2O3–BiOCl/poly-m-methyl aniline nanocomposite thin film for broad-spectrum light-sensing
  112. Green synthesis and characterization of CuO/ZnO nanocomposite using Musa acuminata leaf extract for cytotoxic studies on colorectal cancer cells (HCC2998)
  113. Review Articles
  114. Materials-based drug delivery approaches: Recent advances and future perspectives
  115. A review of thermal treatment for bamboo and its composites
  116. An overview of the role of nanoherbicides in tackling challenges of weed management in wheat: A novel approach
  117. An updated review on carbon nanomaterials: Types, synthesis, functionalization and applications, degradation and toxicity
  118. Special Issue: Emerging green nanomaterials for sustainable waste management and biomedical applications
  119. Green synthesis of silver nanoparticles using mature-pseudostem extracts of Alpinia nigra and their bioactivities
  120. Special Issue: New insights into nanopythotechnology: current trends and future prospects
  121. Green synthesis of FeO nanoparticles from coffee and its application for antibacterial, antifungal, and anti-oxidation activity
  122. Dye degradation activity of biogenically synthesized Cu/Fe/Ag trimetallic nanoparticles
  123. Special Issue: Composites and green composites
  124. Recent trends and advancements in the utilization of green composites and polymeric nanocarriers for enhancing food quality and sustainable processing
  125. Retraction
  126. Retraction of “Biosynthesis and characterization of silver nanoparticles from Cedrela toona leaf extracts: An exploration into their antibacterial, anticancer, and antioxidant potential”
  127. Retraction of “Photocatalytic degradation of organic dyes and biological potentials of biogenic zinc oxide nanoparticles synthesized using the polar extract of Cyperus scariosus R.Br. (Cyperaceae)”
  128. Retraction to “Green synthesis on performance characteristics of a direct injection diesel engine using sandbox seed oil”
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