Volume 86, Issue 8

The effect of the structure of a chromophore on the light-triggered vesicle formation from particles containing the chromophore and a phospholipid was studied. It was revealed that not only the photoactivity but also the amphiphilicity is essential for the chromophore to cause the vesicle formation, where the amphiphilicity likely allows coexistence of the amphiphile and phospholipid in the particles. It was also found that an ionic solute used in the hydration media has an encouraging effect on the photo-generation of vesicles. In addition to these fundamental aspects, vesicle formation in a microenvironment and encapsulation of a substance in the vesicles were also demonstrated.

Fecal incontinence (FI), caused by damage or weakness of the anal sphincter, is a devastating problem for patients experiencing the symptom. Although injectable bulking agents are accepted as a minimally invasive therapeutic technique to treat FI, their short-term efficacy and inability to enhance the anal sphincter function are considered as challenges in clinical practices. In this study, growth factor [nerve growth factor (NGF) and/or basic fibroblast growth factor (bFGF)]-immobilized polycaprolactone (PCL) microparticles were prepared as an injectable bioactive bulking agent that can provide a bulking effect (by microparticles) and stimulate myoblast differentiation or injured muscles around the anus (by the sustained release of growth factors) to enhance the sphincter function for the effective treatment of FI. Pluronic F127-entrapped PCL microparticles were prepared by an isolated particle-melting method. Two different growth factors (NGF and bFGF) were incorporated on the surfaces of the Pluronic F127-entrapped PCL microparticles via heparin binding. The growth factors immobilized on the microparticles were released in a sustained manner over 4 weeks. From cell cultures on the growth factor-immobilized microparticles, it was observed that the myoblasts adhered on the microparticle surfaces showed differences in differentiation into myotubes depending on the growth factor type. In particular, the dual NGF/bFGF-immobilized microparticle group was effective for myogenic differentiation in comparison with the single growth factor (NGF or bFGF)-immobilized groups. The dual NGF/bFGF-immobilized microparticles are suitable to be applied as an injectable bulking agent for the treatment of FI.

Host-defense antimicrobial peptides (AMPs) are a promising lead in the search for novel antibiotics. Many of these peptides exhibit broad-spectrum antibacterial ability, low toxicity toward human cells, and little susceptibility to induction of bacterial resistance. Our research focuses on the development of synthetic polymers that are able to mimic the amphiphilic and cation-rich characteristics of AMPs. This derives bioactive polymers that retain the activity profile of AMPs while utilizing a construct that is less expensive and easier to produce and manipulate chemically. This review details structure–activity relationships (SARs) of a new class of arginine-rich, synthetic AMP mimicking polymers (SAMPs), the guanylated polymethacrylates. These are contrasted with those of amine-based polymers that are mimics of lysine-rich AMPs. The ideal composition for candidates for practical applications was identified as those containing guanidines as a cation source, having a low molecular weight and a low level of lipophilicity. This gave polymers with high potency against Gram-positive strains of bacteria (e.g., Staphylococcus epidermidis MIC = 10 μg/mL) and low toxicity towards human red blood cells (<4% hemolysis at given MIC). This work emphasizes the need to rationalize observed biological activities based not purely on the global lipophilic and cationic character of polymers but rather to consider the profound effect that specific pendant functional groups may have on the potency, selectivity, and mechanisms behind the action of antimicrobial polymers.

A series of thienothiophene-benzotriazole-based semicrystalline copolymers, PTTBTz , PTTBTz-F , and PTTBTz-OR , were synthesized by considering chain linearity, planarity and inter-chain packing by virtue of non-covalent attractive interaction. Fluorine and alkoxy substituents were introduced to modulate the intra- and inter-chain coulombic interactions and crystalline ordering. The fluorine and alkoxy-substituted PTTBTz-F and PTTBTz-OR showed pronounced inter-chain packing with edge-on orientation confirmed by UV-vis absorption and X-ray diffraction measurements. The well-resolved diffraction patterns were obtained for PTTBTz-F and PTTBTz-OR , showing (100)∼(500) inter-lamellar scattering peaks (d-spacing, 17∼18 Å) in the out-of-plane direction and a π-π stacking peak (d-spacing, 3.5∼4.1 Å) in the in-plane direction. Organic field effect transistor (OFET) devices were fabricated with a bottom gate and top contact geometry. PTTBTz-F ( μ h = 4.49 × 10 –2 cm 2 V –1 s –1 , on/off ratio = 1.13 × 10 7 ) and PTTBTz-OR ( μ h = 8.39 × 10 –3 cm 2 V –1 s –1 , on/off ratio = 2.98 × 10 4 ) showed nearly 3 and 2 orders of magnitude higher hole mobility upon annealing at 305 and 260 °C, with compared to the unsubstituted PTTBTz .

Total internal reflection fluorescence (TIRF) is a popular illumination technique in microscopy, with many applications in cell and molecular biology and biophysics. The chief advantage of the technique is the high contrast that can be achieved by restricting fluorescent excitation to a thin layer. We summarise the optical theory needed to understand the technique and various aspects required for a practical implementation of it, including the merits of different TIRF geometries. Finally, we discuss a variety of applications including super-resolution microscopy and high-throughput DNA sequencing technologies.