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Microbial infections and microbial resistance lead to a high demand for new antimicrobial agents. Quaternized polysaccharides are cationic antimicrobial candidates; however, the limitation of homogeneous synthesis solvents that affect the molecular structure and biological activities, as well as their drug resistance remains unclear. Therefore, the authors homogeneously synthesize a series of quaternized chitin (QC) and quaternized chitosan (QCS) derivatives via a green and effective KOH/urea system and investigate their structure–activity relationship and biological activity in vivo and in vitro. Their study reveals that a proper match of degree of quaternization (DQ) and degree of deacetylation (DD′) of QC or QCS is key to balance antimicrobial property and cytotoxicity. They identify QCS‐2 as the optimized antimicrobial agent with a DQ of 0.46 and DD′ of 82%, which exhibits effective broad‐spectrum antimicrobial properties, good hemocompatibility, excellent cytocompatibility, and effective inhibition of bacterial biofilm formation and eradication of mature bacterial biofilms. Moreover, QCS‐2 exhibits a low propensity for development of drug resistance and significant anti‐infective effects on MRSA in vivo comparable to that of vancomycin, avoiding excessive inflammation and promoting the formation of new blood vessels, hair follicles, and collagen deposition to thus expedite wound healing.

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Polyethylenimine‐modified sugarcane bagasse cellulose (SBCMP), as a new adsorbent, was synthesized by the reaction of polyethylenimine (PEI) with sugarcane bagasse cellulose and glutaraldehyde. The adsorption of Cu(II) by SBCMP was pH‐dependent, and the higher removal efficiency of Cu(II) appeared in the range of pH 3.0–6.0. The adsorption isothermal data fitted well with the Langmuir model, and the maximum adsorption capacity of SBCMP was up to 107.5 mg/g. The adsorption kinetics was best described by the pseudo‐second‐order kinetic. The adsorption of Cu(II) by SBCMP was unfavorable at high temperatures, and thermodynamic analyses implied that the adsorption of Cu(II) by SBCMP was an exothermic reaction. Fourier transform infrared spectroscopy (FT‐IR) combined with X‐ray photoelectron spectroscopy (XPS) revealed that Cu(II) adsorption on SBCMP mainly controlled by the nitrogen atoms of NH group in PEI. The results of regeneration cycles showed that SBCMP was suitable for reuse in the adsorption of Cu(II) from aqueous solution. These experimental results suggested that SBCMP is expected to be a new biomass adsorbent with high efficiency in removing Cu(II) from wastewater.

Sensors, displays, and energy storage devices utilized in electronics are undergoing a rapid transition from rigid to flexible and stretchable materials. Traditional electronics-material substrates (metals and semiconductors) have several flaws, including insufficient softness and flexibility and high fragility, resulting in breakage upon stretching and folding. In addition, these materials have limited biodegradability for recycling. Thus, natural polymer hydrogels, with intrinsic biodegradability and biocompatibility, have been recently used to fabricate eco-friendly sensors and flexible energy storage devices. These hydrogels exhibit a vast range of tunable mechanical properties, making them suitable for the fabrication of flexible electronics. Here, dual cross-linked chitin hydrogels with high strength, flexibility, and biodegradability were synthesized using a sequential chemical and physical cross-linking strategy. The dual cross-linked chitin hydrogels exhibited a more comprehensive energy dissipation mechanism than hydrogels that were only physically or chemically cross-linked. Additionally, they could be used as flexible substrates for screen printing, with immense potential applications in the fields of wearable sensors and flexible supercapacitors. Furthermore, the hydrogel-based flexible electronics can be biodegraded in soil or easily recycled in Chitinase solution. This strategy provides a promising route for creating high strength, toughness, and biodegradable chitin hydrogels, which may contribute to the sustainable development of flexible electronics.