Multilayer Assembly of Tannic Acid and an Amphiphilic Copolymer Poloxamer 188 on Planar Substrates toward Multifunctional Surfaces with Discrete Microdome-Shaped Features.

Tannic acid (TA) is a natural polyphenol compound with a broad spectrum of biological activities, the most notable of which being antioxidation. Poloxamer 188 (P188), a synthetic triblock copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), is amphiphilic in nature and best known for its ability to seal structurally damaged cellular membranes. The integration of both substances onto planar substrates could bring a new option for multifunctional coatings that are advantageous for implantable biomedical devices. Here, we demonstrate the feasibility of multilayer assembly of TA/P188 toward such a coating based on hydrogen bonding between phenolic hydroxyls of TA and ether groups of P188, and the unique surface feature it generates. The interactions between these two compounds were studied both in solution and in substrate-supported layer-by-layer assembly. The multilayer assembly process exhibits an exponential growth pattern as characterized by UV-vis spectrophotometry and quartz crystal microbalance with dissipation. Morphologically unique, microdome-shaped surface features emerge and evolve with the number of layers assembled. Such features bring a reservoir function to this coating, as demonstrated by the loading of hydrophobic nile red dye. Furthermore, the presence of TA in the multilayers was revealed by silver nitrate staining, and its antioxidation activity was demonstrated through a 2,2-diphenyl-1-picryl-hydrazyl free-radical scavenging assay.

Amphiphilic Cellulose Nanocrystals for Enhanced Pickering Emulsion Stabilization.

Sulfated cellulose nanocrystals (CNC) with high surface charge density are inadequate for stabilizing oil-water emulsions, which limits their applications as interfacial stabilizers. We performed end-group modification by introducing hydrophobic chains (polystyrene) to CNC. Results showed that the modified CNC are more effective in emulsifying toluene and hexadecane than pristine CNC. Various parameters were investigated, such as concentration of particles, electrolytes, and polarity of solvents on the characteristics of the emulsions. This study provides strategies for the modification of cellulose nanocrystals to yield amphiphilic nanoparticles that enhance the stability of emulsions. Such systems, bearing biocompatible and environmentally friendly characteristics, are attractive for use in a wide range of industries spanning food, biomedicine, pharmaceuticals, cosmetics, and petrochemicals.

Ultrathin alternating copolymer nanotubes with readily tunable surface functionalities.

Well-defined ultrathin nanotubes (30 nm in diameter and of micrometer-scale length) were generated through the self-assembly of a novel alternative copolymer synthesized using an epoxy-thiol click-chemistry reaction. The self-assembly mechanism was investigated both by experiments and using dissipative particle dynamics (DPD) simulations. The obtained nanotubes can be readily functionalized with carboxy groups, amino groups, peptides, or other groups by simple modular click copolymerization.

Cellulose Nanocrystal-ZnO Nanohybrids for Controlling Photocatalytic Activity and UV Protection in Cosmetic Formulation.

A high-performance semiconductor zinc oxide (ZnO) on melamine formaldehyde-coated cellulose nanocrystals (MFCNCs) was synthesized and evaluated for its application in smart cosmetics. These ZnO@MFCNC hybrid nanostructures were evaluated for their in vitro sun protection factor performance and photocatalytic activity under simulated UV and solar radiation. The photodegradation kinetics of a model pigment (methylene blue) was fitted to the Langmuir-Hinshelwood model. A 4-fold increase in the photocatalytic activity of ZnO@MFCNCs was observed when compared to pure ZnO. This is associated with (i) increased specific surface area provided by the MFCNC template, (ii) confined surface energy and controlled growth of ZnO nanoparticles, and (iii) entrapment of photoinduced charge carriers in the pores of the core-shell MFCNC rod, followed by fast promotion of interfacial e-charge transfer to the surface of the catalyst. The present study demonstrates how an increase in photocatalytic activity can be engineered without the introduction of structural defects or band gap tailoring of the semiconductor. The aqueous-based ZnO@MFCNC hybrid system displayed attractive UV-absorption and photocatalytic characteristics, offering the conversion of this renewable and sustainable technology into intelligent cosmetic formulations.

Water-based synthesis of cationic hydrogel particles: effect of the reaction parameters and in vitro cytotoxicity study.

Micro/nanoscale hydrogel particles are of great interest for biomedical applications, such as carriers for therapeutic delivery. Compared to conventional hydrogel particles that are mainly composed of vinylic monomers, we have introduced a simple methodology to prepare multi-functional cationic hydrogel particles by adopting the epoxy-amine chemistry in water exemplifying "click" characteristics. Herein, we investigate the effects of key reaction parameters, including time, temperature, reactant concentration and amine-epoxy stoichiometric ratio, on the preparation and properties of such hydrogel particles. Our results indicated that the aforementioned parameters could greatly impact the particle formation. The hydrodynamic diameter, surface charge, and morphology of the resultant particles were characterized by dynamic light scattering and scanning electron microscopy. Particle size was inversely correlated with the following reaction parameters: reaction time, temperature, and reactant concentration. This is likely due to the influence of the parameters on the formation of the intermediate thermosensitive prepolymers. Different reaction conditions yielded a wide range of particle surface charges, varying from +47 mV to +71 mV. Morphological analysis also revealed significant effects induced by the variation of reaction time and temperature. All particles exhibited a temperature-dependent swelling property. However, the extent of swelling and sensitivity varied depending on the reaction conditions. Finally, in vitro cytocompatibility studies based on murine RAW264.7 macrophages showed the particle acute cytotoxicity being dose and surface charge dependent. Cytocompatibility of the cationic hydrogel particles was improved by reducing the surface charges with variation of the synthesis conditions.

Enhanced colloidal stability and antibacterial performance of silver nanoparticles/cellulose nanocrystal hybrids.

The aggregation of nanoparticles has been shown to significantly reduce the activity of nanomaterials, resulting in inferior performance. As an alternative to the use of traditional capping agents, stabilization of unstable nanoparticles with water-dispersible and biocompatible carriers is a promising strategy. A bioinspired coating strategy was developed and the hybrid nanoparticles displayed excellent colloidal stability that significantly improved antibacterial activity when silver nanoparticles (AgNPs) were used as a model. Cellulose nanocrystals (CNCs) were first modified with dopamine, followed by in situ generation and anchoring of AgNPs on the surface of CNCs through the reduction of silver ions by polydopamine coated CNCs. The results indicated that the dispersion stability of AgNPs was significantly enhanced by the CNC, which in turn resulted in more than fourfold increase in antibacterial activity based on antibacterial studies using Escherichia coli and Bacillus subtilis.

Fluorinated raspberry-like polymer particles for superamphiphobic coatings.

Raspberry-like (RB) polymer particles were prepared, fluorinated, and cast onto glass plates to yield highly water- and oil-repellant superamphiphobic particulate coatings. To procure the RB particles, glycidyl-bearing 212 and 332 nm particles (abbreviated as s-GMA and l-GMA, respectively) were first prepared via surfactant-free free radical emulsion polymerization. Reacting the glycidyl groups of the l-GMA particles with 2,2'-(ethylenedioxy)bis(ethylamine) (EDEA) produced large amine-functionalized particles (l-NH2). The l-NH2 particles were then reacted with an excess of the s-GMA particles to create RB particles. For surface fluorination, the residual glycidyl groups of the smaller s-GMA particles surrounding the central l-NH2 core of the RB particles were first converted to amino groups by reaction with EDEA. The purified amino-bearing particles were subsequently reacted with an excess of a statistical copolymer poly(2-(perfluorooctyl)ethyl methacrylate-co-glycidyl methacrylate), P(FOEMA-co-GMA). Casting these particles onto glass plates yielded particulate films that exhibited static contact angles of 165 ± 2°, 155 ± 3°, 152 ± 4°, and 143 ± 1° and droplet rolling angles of <1 °, <1 °, 7 ± 2°, and 13 ± 2° for water, diiodomethane, corn-based cooking oil, and hexadecane droplets, respectively. These results demonstrated that this practical bottom-up approach could be used to produce superamphiphobic coatings.

Facile aqueous-phase synthesis of multi-responsive nanogels based on polyetheramines and bisepoxide.

A new strategy for the preparation of nanogels from commercially available monomers of bisepoxide and aliphatic polyetheramine has been developed. The nanogels are generated in a one-pot process through aggregation polymerization of an in situ formed thermal sensitive intermediate polymer in an additive-free and catalyst-free aqueous environment. Such a facile process allows easy size tuning of the gel particles from the nanometer to the micron scale, simply by adjusting the reactant concentration. The obtained nanogels demonstrated responsiveness to multiple biologically relevant stimuli, including temperature, pH, and oxidation. Nile red was encapsulated in the nanogels as a model hydrophobic drug. In vitro drug release studies showed stimuli-triggered release from the nanogels, suggesting the potential for controlled drug delivery.

Facile preparation of novel peptosomes through complex self-assembly of hyperbranched polyester and polypeptide.

This work reported for the first time a facile template-free method to prepare polypeptide-based vesicles (peptosomes) through one-step complex self-assembly of carboxyl-terminated hyperbranched polyester and cationic poly-l-lysine (PLL). The preparation of such peptosomes, named complex peptosomes (CPs) here, is very simple just by mixing two kinds of polymer aqueous solutions together. The CP size can be readily controlled from nanosize to microsize through the adjustment of polymer concentration. The resulting nanosized CPs show unexpected size stability independent of a broad solution pH range, long-term storage stability, and almost no cytotoxicity and have demonstrated great potential to be used as the carriers in drug delivery.