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Rapid and accurate evaluation of pollutant contamination in water is one of the key tasks of environmental monitoring. To make onsite assessment feasible, the analytical tools should be easy to operate, with minimal sample preparation needs. Gold nanoparticle (AuNP)-based sensors have the potential to detect toxins, heavy metals, and inorganic and organic pollutants in water rapidly with high sensitivity, and they are expected to play an increasingly important role in environmental monitoring. In this article, the synthesis, fabrication and functionalization of AuNPs are discussed, and the recent advances in the development and application of AuNP-based sensors for the determination of various pollutants contamination in water are reviewed.

Marine toxins are a food safety concern worldwide. This review discusses current analytical methods for those toxins that are legally regulated in Europe, namely domoic acid, saxitoxin, okadaic acid, yessotoxin, pectenotoxin and azaspiracids, and all their analogues, and those that are not regularly monitored but are a threat to humans, such as tetrodotoxin, ciguatoxins and cyclic imines. Because of legislative changes that were implemented in 2011, most legally required methods are chromatographic. Saxitoxin and domoic acid are monitored by high-performance liquid chromatography with fluorescent and ultraviolet detection, respectively. All other toxins are monitored nowadays by means of chromatographic separation and mass spectrometry detection.

Chitin, a small organic molecule commonly found in fungal cell walls and insect exoskeletons, has the ability to elicit an immune response in plants by binding to specific membrane-bound receptors. Understanding how plants detect and fend off deleterious fungi and insects will enable improved defense strategies against these pathogens. A wide array of techniques, including affinity binding studies, isothermal calorimetry, structural analysis, and molecular genomic methods have been used to identify and characterize chitin-binding receptors as well as the kinetic parameters of chitin-receptor interactions. There are a number of newly developed analytical technologies in mechanical, electrochemical, and optical biosensing that have great potential to further elucidate the interactions between chitin and its binding partners. In this review, we provide a detailed examination of the methods currently used to characterize chitin-binding interactions, along with emerging analytical techniques that have the potential to transform this area of study.

The inelastic scattering of light, Raman scattering, presents a very low cross section. However, the signal can be amplified by several orders of magnitude, leading to the so-called surface-enhanced Raman scattering (SERS) phenomenon. Basically, the SERS effect is achieved when the target molecule (analyte) is adsorbed onto metallic nanoparticles, usually noble metals. This article presents an overview of the applications of SERS to cancer diagnosis and the detection of pesticides, explosives, and drugs (illicit and pharmacological). SERS is routinely applied nowadays to detect and identify analytes at very low concentrations, including for single-molecule detection. However, the application of SERS as an analytical tool requires reliable and reproducible SERS substrates, in terms of enhancement factors, which depends on the size, shape, and aggregation of the metallic nanoparticles. Therefore, the production of reliable and reproducible SERS substrates is a challenge in the field. Besides, the metallic nanoparticles can also induce changes in the system by possible interactions with the analyte under investigation, which must be taken into account. This review will present work in which, under certain specific experimental conditions, SERS has been analytically applied.

Bacterial infection represents one of the leading causes of disease and death, and as such, bacterial detection is an important step in managing infectious diseases. The current protocol requires growing cell cultures, which can take several days. Fast detection of low copies of bacterial cells has thus posed an analytical challenge. Among the new strategies developed to achieve this goal, functional nucleic acids (FNAs) have emerged to be a promising platform. FNAs include DNAzymes, aptamers, and aptazymes, all of which can recognize analytes other than complementary nucleic acids. FNAs are obtained using a combinatorial biology technique called systematic evolution of ligands by exponential enrichment (SELEX). FNAs have been isolated against not only purified proteins and surface markers from bacterial cells but also whole cells. A diverse range of signaling mechanisms including fluorescence, color, and electrochemistry-based detection has been reported. Although the majority of current sensors cannot achieve single-cell sensitivity, with improved combinatorial selection techniques and the incorporation of nanomaterials to realize multivalent binding and signal amplification, FNAs represent a feasible solution for bacterial detection.