Mussel-Mimetic Hydrogel Coating with Anticoagulant and Antiinflammatory Properties on a Poly(lactic acid) Vascular Stent.

Biodegradable stents are the most promising alternatives for the treatment of cardiovascular disease nowadays, and the strategy of preparing functional coatings on the surface is highly anticipated for addressing adverse effects such as in-stent restenosis and stent thrombosis. Yet, inadequate mechanical stability and biomultifunctionality limit their clinical application. In this study, we developed a multicross-linking hydrogel on the polylactic acid substrates by dip coating that boasts impressive antithrombotic ability, antibacterial capability, mechanical stability, and self-healing ability. Gelatin methacryloyl, carboxymethyl chitosan, and oxidized sodium alginate construct a double-cross-linking hydrogel through the dynamic Schiff base chemical and in situ blue initiation reaction. Inspired by the adhesion mechanism employed by mussels, a triple-cross-linked hydrogel is formed with the addition of tannic acid to increase the adhesion and antibiofouling properties. The strength and hydrophilicity of hydrogel coating are regulated by changing the composition ratio and cross-linking degree. It has been demonstrated in tests in vitro that the hydrogel coating significantly reduces the adhesion of proteins, MC3T3-E1 cells, platelets, and bacteria by 85% and minimizes the formation of blood clots. The hydrogel coating also exhibits excellent antimicrobial in vitro and antiinflammatory properties in vivo, indicating its potential value in vascular intervention and other biomedical fields.

One-step synthesis of golf ball-like thiol-functionalized silica particles.

There is increasing interest in the synthesis of golf ball-like particles. Most of the reports on golf ball-like particles have focused on polymer particles, while relatively few are concerned with inorganic particles. In this work, golf ball-like thiol-functionalized silica particles were synthesized for the first time by a one-step sol-gel reaction using 3-mercaptopropyl trimethoxysilane (MPTMS) and tetraethoxysilane (TEOS) as the precursors. The particle growth with time was monitored by SEM and a particle formation mechanism was proposed. The effects of different reaction parameters including the TEOS/MPTMS molar ratio, the NH4OH concentration, and the stirring rate on the morphology and size of the golf ball-like organosilica particles were studied. Given that the thiol groups have versatile functionalities, golf ball-like thiol-functionalized silica particle is a useful model for academic studies.

Environmentally Friendly and Broad-Spectrum Antibacterial Poly(hexamethylene guanidine)-Modified Polypropylene and Its Antifouling Application.

Biological fouling is one of the main reasons that limits the application of traditional polypropylene (PP) fishing nets in aquaculture. Here, a new environmentally friendly and broad-spectrum antibacterial agent called cationic poly(hexamethylene guanidine) (PHMG) was grafted onto PP molecular chains via permanent chemical bonding to inhibit the biological fouling. The antibacterial monofilaments were obtained by blending different contents of PP-g-PHMG with PP by melt spinning. FTIR results found PHMG to be stably present in the mixed monofilaments after high-temperature melt spinning molding. The crystallinity, relaxation behavior, mechanical properties, water absorptivity, and antibacterial and antifouling efficiencies of the PP-g-PHMG/PP blends were strongly dependent on PP-g-PHMG. The crystallinity increased with increasing PP-g-PHMG content. Adding PP-g-PHMG improved the breaking strength, knotting strength, and elongation at the break for all ratios of PP-g-PHMG/PP blends. However, the water absorption caused by PHMG is low, ranging between 2.48% and 3.45% for the PP-g-PHMG/PP monofilaments. The monofilaments showed excellent nonleaching antimicrobial activities against Staphylococcus aureus and Escherichia coli. The electrostatic adsorption of the negatively charged bacteria and the destruction of their cell membrane allowed the growth inhibition to reach 99.69% with a PP-g-PHMG content of 40%. The marine fish farming experiment also showed a long-term antifouling effect.

An injectable anti-microbial and adhesive hydrogel for the effective noncompressible visceral hemostasis and wound repair.

An in-situ formed hemostatic hydrogel (GelMA/OD/Borax) was prepared for the emergency wound hemostasis and anti-inflammation applications. Gelatin was chosen as the backbone and modified with methacrylic anhydride (MA) to synthesize GelMA, which showed the admirable UV light activatable polymerizing ability. Aldehyde groups, which cross-linked with the -NH2 on the tissue surface and afforded the tissue adhesion, were produced by oxidizing the o-hydroxyl groups of dextran. Further, the sodium tetraborate formed dynamic boric acid ester bonds with the oxidized dextran (OD). With this triple-network structure, the as-prepared hydrogel presented excellent hemostatic capacity and surmounted a high blood pressure of 165 mmHg, which is higher than the threshold systolic blood pressure of healthy adults (i.e., 120 mmHg). The mechanical property, morphology, biocompatibility and degradation of the hydrogel were character Borax, the hydrogel successfully blocked the bleeding and accelerated the wound healing. This research provides a new modality for the design of a multifunctional hemostatic hydrogel for effective hemostasis and wound healing.

Influence of Acidity and Oxidant Concentration on the Nanostructures and Electrochemical Performance of Polyaniline during Fast Microwave-Assisted Chemical Polymerization.

Polyaniline (PANI), a typical conducting polymer, has attracted great interest as an electrode material. A series of PANIs were prepared through fast microwave-assisted chemical oxidative polymerization with varying HCl and APS concentrations here. It was found that the microwave synthesized PANIs had ~4 times higher for the yields and 7~10 times higher for the electrical conductivity in comparison to PANI samples prepared using conventional method. PANI nanosheets could easily be fabricated in weakly acidic solution due to their oligomeric structure, which contained flat phenazine rings. By contrast, linear PANI chains produced in highly acidic solutions formed nanofibers. The APS concentration did not significantly affect the molecular structures of PANIs under the conditions here. However, increasing the concentration of APS produced nanofibers with shorter branches, which may be due to secondary nucleation during chain growth resulting from increases in active initiation centers. The electrical conductivity and electrochemical performance of PANIs were both improved with increasing HCl and APS concentrations. Improvements due to increases in HCl concentration may be attributed to additions in conjugation length and enrichment of doping levels, while improvements due to increases in APS concentration could be attributed to the increased crystallinity of PANI, which facilitates ion transport.

Fabrication of Vertical Array CNTs/Polyaniline Composite Membranes by Microwave-Assisted In Situ Polymerization.

A vertical array carbon nanotubes (VACNTs)/polyaniline (PANi) composite membrane was prepared by microwave-assisted in situ polymerization. With microwave assistance, the morphology of PANi revealed a smaller diameter and denser connection. Meanwhile, thermogravimetric analysis showed improved thermal stability of microwave-assisted PANi for higher molecular weight. Focused ion beam thinning method was used to cut the VACNTs/PANi membrane into dozen-nanometer thin strips along the cross-sectional direction, and transmission electron microscopy observation showed seamless deposition of PANi between VACNT gaps, without damaging the vertical status of CNTs. Meanwhile, stronger conjugate interaction between the quinoid ring of PANi and VACNTs of the composite membrane were prompted by microwave-assisted in situ polymerization. By using nanoindentation technology, the VACNTs/PANi composite membrane showed exponential increasing of modulus and hardness. Meanwhile, the elasticity was also improved, which was proved by the calculated plastic index. The results can provide helpful guidance for seamlessly infiltrating matrix into CNT array and also demonstrate the importance of structural hierarchy for getting proper behavior of nanostructures.

Influence of annealing on chain entanglement and molecular dynamics in weak dynamic asymmetry polymer blends.

The influence of annealing above the glass transition temperature (T(g)) on chain entanglement and molecular dynamics of solution-cast poly(methyl methacrylate)/poly(styrene-co-maleic anhydride) (PMMA/SMA) blends was investigated via a combination of dynamic rheological measurement and broadband dielectric spectroscopy. Chain entanglement density increases when the annealing temperature and/or time increases, resulting from the increased efficiency of chain packing and entanglement recovery. The results of the annealing treatment without cooling revealed that the increase of the entanglement density occurred during the annealing process instead of the subsequent cooling procedure. Annealing above T(g) exerts a profound effect on segmental motion, including the transition temperature and dynamics. Namely, T(g) shifts to higher temperatures and the relaxation time (τ(max)) increases due to the increased entanglement density and decreased molecular mobility. Either T(g) or τ(max) approaches an equilibrium value gradually, corresponding to the equilibrium entanglement density that might be obtained through the theoretical predictions. However, no obvious distribution broadening is observed due to the unchanged heterogeneous dynamics. Furthermore, side group rotational motion could be freely achieved without overcoming the chain entanglement resistance. Hence, neither the dynamics nor the distribution width of the subglass relaxation (ß- and γ-relaxation) processes is affected by chain entanglement resulting from annealing, indicating that the local environment of the segments is unchanged.