Controlled Hydration, Transition, and Drug Release Realized by Adjusting Layer Thickness in Alginate-Ca2+/poly(N-isopropylacrylamide) Interpenetrating Polymeric Network Hydrogels on Cotton Fabrics

Strength, pliability, and hydrophobicity of mung bean starch straws: Orientation change caused by annealing time

To achieve starch straws with high strength and large toughness, the effects of annealing time on structural and functional performances of mung bean starch straws were studied. The results revealed that with increasing annealing time from 0to 60 min, the ratios of 1047 cm-1/1022 cm-1 in Fourier transform infrared spectroscopy decreased from 1.37 to 1.20, and the relative crystallinities decreased from 12.09% to 11.01%. The relative crystallinity increased to 13.28% when annealing time increased to 120 min. The maximum bending force increased from 10.93 to 104.24 N, and modulus of elasticity enhanced from 0.93 to 62.68 N/mm when annealing time increased from 0 to 120 min. Starch straws annealed for 120 min had the lowest water absorption (94.61%), while starch straws annealed for 60 min had the highest water absorption (127.38%). This outcome not only lay a theoretical foundation for preparing biodegradable starch straws with excellent performance, but also apply for beverages, food container, food packaging films, and so on, strongly promoting starch industrial transformation and development.

Natural Phytic Acid-Assisted Polyaniline/Poly(vinyl alcohol) Hydrogel Showing Self-Reinforcing Features

Polyaniline (PANi) hydrogels that combine advantages of hydrogels and conductive PANi have recently emerged in areas of wearable devices and personal healthcare. Nevertheless, their mechanical performance often gradually degrades after being used for a period, caused by destruction of the inner structures when external forces are applied. Inspired by biological structures with persistent durability, we develop here a phytic acid-assisted PANi/poly(vinyl alcohol) (PVA) hydrogel that shows self-reinforcing features. As a natural product holding plenty of phosphate groups, phytic acid (PA) plays two crucial roles when preparing this hydrogel: (1) aniline is salinized by PA in aqueous solution to promote in situ polymerization, making the resulting PANi conductive; (2) PA/PANi particles form hydrogen bonds with PVA, acting as stress concentration points to induce structure orientation. The optimal PVA/PA/PANi hydrogel displays dark green color with a uniform distribution of PA/PANi particles. After experiencing repetitive 4 × 100 stretching at a strain of 10%, the hydrogel exhibits an enhanced fracture strength (20.35 MPa), Young's modulus (22.66 MPa), and toughness (36.24 MJ·m-3) compared with the original hydrogel. This self-reinforcing feature is mainly attributed to the formation of anisotropic structures fixed by hydrogen bonds between PA/PANi particles and PVA chains upon repetitive external forces. Moreover, anisotropic structures can be disassembled by swelling the post-stretched hydrogel in water, and the swollen hydrogel shows similar self-reinforcing behaviors. The good mechanical durability and reusable characteristics make the PVA/PA/PANi hydrogel a reliable strain sensor. This work provides a structural growing-reviving approach for conductive hydrogels with persistent durability.

Metal ions doping effect on the physicochemical, antimicrobial, and wound healing profiles of alginate-based composite

The alginate (Alg) matrix with immobilized hydroxyapatite (HAp) and zinc oxide (ZnO), cross-linked by chitosan (CS) and metal ions (Meⁿ⁺) Ca²⁺, Zn²⁺, and Cu²⁺ was created as a wound dressing. The effect of Meⁿ⁺ and their concentrations on water vapor transition, fluid handling, dehydration, drug release, and healing are shown. Me-containing samples have a lower sorption capacity, than a commercial Kaltostat, however, a much lower degree of their dehydration provides a longer wound wet. The Meⁿ⁺ presence lowers the environmental pH to slightly acidic values promoting healing. Ca²⁺, Zn²⁺, and Cu²⁺ in complexes with CS increase antimicrobial effect against E. coli and S. aureus, slow down the Anaesthesine release, making it compatible with Fickian diffusion in the Zn²⁺ and Cu²⁺ presence, and non-Fickian transport under Ca²⁺ influence. The material promotes the proliferation of the fibroblasts, an increase of collagen fibres, and new arterial and venous capillaries, indicating the intensity of the healing process.