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Vitiligo is a chronic depigmenting disorder of the skin and mucosa caused by the destruction of epidermal melanocytes. Although the exact mechanism has not been elucidated, studies have shown that oxidative stress plays an important role in the pathogenesis of vitiligo. High mobility group box protein B1 (HMGB1) is a major nonhistone protein and an extracellular proinflammatory or chemotactic molecule that is actively secreted or passively released by necrotic cells. Recent data showed that HMGB1 is overexpressed in both blood and lesional specimens from vitiligo patients. Moreover, oxidative stress triggers the release of HMGB1 from keratinocytes and melanocytes, indicating that HMGB1 may participate in the pathological process of vitiligo. Overall, this review mainly focuses on the role of HMGB1 in the potential mechanisms underlying vitiligo depigmentation under oxidative stress. In this review, we hope to provide new insights into vitiligo pathogenesis and treatment strategies.

The cholesterol-functionalized polycarbonate-based diblock copolymer, PEG(113)-b-P(MTC-Chol)(30), forms pathway-dependent nanostructures via dialysis-based solvent exchange. The initial organic solvent that dissolves or disperses the polymer dictates a self-assembly pathway. Depending upon the initial solvent, nanostructures of disk-like micelles, exhibiting asymmetric growth and hierarchical features, are accessible from a single amphiphilic precursor. Dioxane and tetrahydrofuran (THF) molecularly dissolve the block copolymer, but THF yields disks, while dioxane yields stacked disks after dialysis against water. Dimethylformamide and methanol display dispersed disks and then form stacked disk structures after dialysis. The path-dependent morphology was correlated to solubility parameters, an understanding of which offers routes to tailor self-assemblies with limited sets of building blocks.

The cholesterol-functionalized polycarbonate-based diblock copolymer, PEG113-b-P(MTC-Chol)30, forms pathway-dependent nanostructures via dialysis-based solvent exchange. The initial organic solvent that dissolves or disperses the polymer dictates a self-assembly pathway. Depending upon the initial solvent, nanostructures of disk-like micelles, exhibiting asymmetric growth and hierarchical features, are accessible from a single amphiphilic precursor. Dioxane and tetrahydrofuran (THF) molecularly dissolve the block copolymer, but THF yields disks, while dioxane yields stacked disks after dialysis against water. Dimethylformamide and methanol display dispersed disks and then form stacked disk structures after dialysis. The path-dependent morphology was correlated to solubility parameters, an understanding of which offers routes to tailor self-assemblies with limited sets of building blocks. Agency for Science, Technology and Research (A*STAR) Published version

There is an urgent need for effective bactericidal agents for use in real commercial formulations because many old disinfectants, such as halogenated compounds, are now banned. Cationic polymers may have good bactericidal properties in pure water or buffer but typically become ineffective in the presence of anionic surfactants that are widely used in many commercial formulations. Here, we discover that polyion complex (PIC) nanoparticles formed by cationic polymers of poly[3-(acrylamido)propyl]trimethylammonium chloride (PAMPTMA) in the presence of anionic surfactants display a promising fast-bactericidal effect (>99.99% killing within a 10 min treatment) on Gram-negative Escherichia coli (ATCC 8739). To examine the influence of the hydrophobicity on the bactericidal property, we synthesize PAMPTMA-b-poly(butyl methacrylate) and discover that increasing the hydrophobicity has little influence on the bactericidal property of PIC nanoparticles. A mechanism study shows that cationic PIC nanoparticles rapidly cause significant pores in both the outer and inner membranes because of their large size and high local concentration of positive charges. Rapid membrane pore formation results in fast cell death. The discovery—certain cationic polymers when formulated with anionic surfactants are even more bactericidal than neat cationic polymers alone—paves the way for potential applications of synthetic cationic polymers in commercial formulations. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) MOH (Min. of Health, S’pore) Accepted version

Star polymers with a cross-linked nanogel core are promising carriers of cargo for therapeutic applications due to the synthetic control of amphiphilicity of arms and stability at infinite dilution. Three nanogel-core star polymers were investigated to understand how the arm-block chemical structure controls loading efficiency of a model drug, ibuprofen, and its spatial distribution. The spatial distribution profiles of hydrophobic core, hydrophilic corona, and encapsulated drug were determined by small-angle neutron scattering (SANS). SANS provides the nanometer-scale sensitivity to determine how the arm-block chemistry enhances the sequestering of ibuprofen. Validated molecular dynamics simulations capture the trends in drug profile and polymer segment distribution with further details on drug orientation distribution. This work provides a basis to study structure–function relationships in macromolecular-based carriers of cargo and represents a path toward validated and predictive simulation.

The closed assembly transition from polymers to micelles and open assembly to clusters are induced by supramolecular π–π stacking in model oligocarbonate–fluorene (F-TMC) end-group telechelic polymers. The critical micelle concentration (CMC) depends on the F-TMC degree of polymerization that further controls the weak micelle association and strong clustering of micelles regimes. Clustering follows a multistep equilibria model with average size scaling with concentration reduced by the CMC as R ∼ (c/CMC)1/4. The F-TMC packing that drives the supramolecular self-assembly from polymers to micelles stabilizes these larger clusters. The clusters are characterized by internal relaxations by dynamic light scattering. This signifies that while F-TMC groups drive the clustering, the micelles interconnected via F-TMC bridging interactions remain coupled to the extent that the clusters relax via Rouse–Zimm dynamics, reminiscent of microgels.

Spherical Poly(3-hexylthiophene)-azide-[6,61-phenyl-C61-butyric acid methyl ester (P3HT-azide-PCBM) microgel was synthesized by introducing an azide cross-linkable group into the conjugated polymer. Its UV-vis spectrum shifts blue as a result of the systematic disruption of planarity along the P3HT backbone and a reduction in long range conjugation. And the corresponding fluorescence spectrum also indicates that a strong intra-molecular photo-induced electron transfer is originated from the covalent linkage of PCBM moiety to the P3HT backbone via the hexyl bridge upon photoexcitation. Combined Gel Permeation Chromatography (GPC), dynamic and static light scattering (DLS and SLS) measurements prove that the resultant P3HT-azide-PCBM copolymer is a uniform spherical microgel with a hydrodynamic radius of 130 nm at room temperature. The spherical P3HT-azide-PCBM microgel can be used as electron donor or compatibilizer in bulk-heterojunction (BHJ) devices, but its introduction reduces the photovoltaic performance compared with the blend of P3HT/PCBM, because the hole mobility in the crosslinked polythiophene backbones is largely decreased.

Triblock polyelectrolyte gels were characterized by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). The oppositely charged end blocks self-assemble into polyelectrolyte complex cores, while the neutral poly(ethylene oxide) middle block bridges adjacent cores. The size of the polyelectrolyte complex core does not change with temperature. However, the neutral middle block displays a temperature-dependent conformation. The liquid-like order of the complex core within the gel phase leads to stretched bridging chains that approach their unperturbed dimensions with increasing concentration. A stretch ratio for bridging chains was defined as the ratio between stretched and unperturbed dimensions. A further reduction in the chain stretching occurs with increasing temperature due to solvent quality. DLS observes multiple modes consistent with a collective diffusion (fast mode) and diffusion of clusters (slow mode). The dynamics of these clusters are at length scales associated with the SANS excess scattering, but with relaxation time near the crossover frequency observed by mechanical spectroscopy.

A fluorescent pyrene probe method was applied to measure the critical micelle concentration (CMC) of oligocarbonate-fluorene end-functionalized poly(ethylene glycol) (F(m)E(445)F(m)) triblock copolymers in water. The CMC decreases with lower temperature and higher values of the hydrophobic block length, m. When analyzed by a closed-assembly micelle model, the estimated energetic parameters find a negative ΔH°(mic) and small positive ΔS°(mic) suggestive of enthalpy-driven micellization, which differs from entropy-driven oxyethylene/oxybutylene triblock copolymers and octaethylene glycol-n-alkyl ethers. The enthalpy-driven micellization of F(m)E(445)F(m) may result from the limited hydration of individual hydrophobic F blocks that leads to few hydrogen-bonded waters released during F block association. The π-π stacking oligocarbonate-fluorene system also observed enthalpy-entropy compensation when compared to a series of published data on diblock and triblock copolymer systems. An anomalously low partition equilibrium constant for m = 15.3 implies a tightly-packed core that excludes pyrene intercalation into the fluorene core. This is discussed along with the possible limited applicability to estimate the CMC and potential model drug molecule insertions into the intercalated micelle core.

A series of microgel particles composed of a polystyrene (PS) core and a thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) shell with different shell thicknesses were investigated to elucidate the effect of microgel softness on its shear thickening behavior. Since the softness of the microgels increases with decreasing temperature through the volume phase transition effect of PNIPAM shell, the measured softness parameter, n, which is derived from the Zwanzig-Mountain equation, was used to measure and describe the combined influences of temperature and shell thickness. Confocal microscopy is used to investigate the interaction potential between microgel particles with different softness parameters. According to the obtained results, the softness parameter can provide an estimate for the shear thickening behavior of microgel suspensions, at least semi-quantitatively.

The mechanism of charge-transfer complexation in electron-donor (D)/electron-acceptor (A) active layer was studied for a pseudobinary blend model system, poly(4-vinylpyridine) (P4VP)/[6,6]-phenyl-C...

The mechanism of two-dimensional (2D) crystal formation from an air-drying suspension of soft microgel particles is investigated via in situ confocal laser scanning microscopy (CLSM). According to the time-resolved radial distribution function g(r), the process can be divided into two separate stages, i.e., nucleation and growth. During the air-drying process, the soft poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) spherical microgel particles first deform into a disk-like shape as the thickness of the concave water layer becomes comparable to their diameter. Subsequently, the particles are driven together by attractive capillary forces to initiate the nucleation process. Once the critical nuclei size is reached, the 2D nuclei can then grow into a crystal. Subsequently, during the crystal growth process, convective water flow compels free microgel particles from the liquid phase to the crystal growth front. While trapped in the growth front, the particles rearrange themselves into crystal structures. The size of 2D crystals increases quadratically with time. Ideally, these findings will promote more experimental and theoretical work aimed at elucidating the 2D fluid-to-solid transition of soft microgel particles, as well as 2D soft disk crystal growth in condensed matter physics.