Synthesis and Fluorescent Thermoresponsive Properties of Tetraphenylethylene-Labeled Methylcellulose.

Functional polymer, especially the one based on renewable and sustainable materials, has attracted increasing attention to satisfy the growing demand for the design of stimuli-responsive devices. Methylcellulose (MC) is a water-soluble derivative of cellulose, which has been widely used in many fields for its biocompatibility and biological inertness. In this work, MC is labeled by tetraphenylethylene (TPE) via azide-alkyne click reaction to obtain a fluorescent cellulose-based derivative of MC-TPE. The degree of substitution of MC-TPE is determined to be 0.074, which can be self-assembled into micelles in water with the size of 42 ± 6 nm. MC-TPE shows thermoresponsivity and thermoreversibility in size, transmittance, and fluorescence, enabling it to work as a fluorescent thermosensor. Moreover, MC-TPE exhibits nontoxicity and biocompatibility, allowing its application in MCF-7 cell imaging. Therefore, this newly functional natural polymer shows promising potentials in the fields of sensing and bioimaging.

Moisture loss inhibition with biopolymer films for preservation of fruits and vegetables: A review.

In cold storage, fruits and vegetables still keep a low respiratory rate. Although cold storage is beneficial to maintain the quality of some fruits and vegetables, several factors (temperature and humidity fluctuations, heat inflow, air velocity, light, etc.) will accelerate moisture loss. Biopolymer films have attracted great attention for fruits and vegetables preservation because of their biodegradable and barrier properties. However, there is still a certain amount of water transfer occurring between storage environment/biopolymer films/fruits and vegetables (EFF). The effect of biopolymer films to inhibit moisture loss of fruits and vegetables and the water transfer mechanism in EFF system need to be studied systematically. Therefore, the moisture loss of fruits and vegetables, crucial properties, major components, fabrication methods, and formation mechanisms of biopolymer films were reviewed. Further, this study highlights the EFF system, responses of fruits and vegetables, and water transfer in EFF. This work aims to clarify the characteristics of EFF members, their influence on each other, and water transfer, which is conducive to improving the preservation efficiency of fruits and vegetables purposefully in future studies. In addition, the prospects of studies in EFF systems are shown.

Chitosan-based hydrogels with injectable, self-healing and antibacterial properties for wound healing.

Developing an efficient and available material for improved cutaneous tissue regeneration is a major challenge in healthcare. Inspired by the concept of moist wound healing, the injectable and self-healing adenine-modified chitosan (AC) hydrogels are designed to significantly accelerate wound healing without the addition of therapeutic drugs. A series of AC derivatives with degree of substitution (DS) ranging from 0.21 to 0.55 were synthesized in aqueous solutions, and the AC hydrogels were prepared by a simple heating/cooling process. AC hydrogels presented good self-healing, low swelling rate capacity, biocompatibility, promote cell proliferation and excellent hemostatic effect. The hydrogels displayed excellent antibacterial activities against gram-negative bacteria, gram-positive bacteria, fungi and drug-resistance bacteria. Moreover, the full-thickness skin defect model experiments showed that AC hydrogels could reduce inflammatory cell infiltration and accelerate wound healing significantly. The hydrogel can shed new light on designing of the multifunctional dressings for wound healing.

Novel multifunctional adenine-modified chitosan dressings for promoting wound healing.

Wound healing is a dynamic and intricate process, and newly dressings are urgently needed to promote wound healing over the multiple stages. Herein, two water-soluble adenine-modified chitosan (CS-A) derivatives were synthesized in aqueous solutions and freeze-dried to obtain porous sponge-like dressings. The novel derivatives displayed antibacterial activities against S. aureus and E. coli. Moreover, CS-A derivatives demonstrated excellent hemocompatibility and cytocompatibility, as well as promoted the proliferation of the wound cells by shortening the G1 phase and improving DNA duplication efficiency. The ability of CS-A sponges to promote wound healing was studied in a full-thickness skin defect model. The histological analysis and immunohistochemical staining showed that the wounds treated with CS-A sponges displayed fewer inflammatory cells, and faster regeneration of epithelial tissue, collagen deposition and neovascularization. Therefore, CS-A derivatives have potential application in wound dressings and provide new ideas for the design of multifunctional biomaterials.

Preparation of a novel antibacterial chitosan-poly(ethylene glycol) cryogel/silver nanoparticles composites.

Cryogel was synthesized through cryogelation of methacrylated carboxymethyl chitosan (mCMC) and poly(ethylene glycol) diacrylate (PEGDA) precursors by photopolymerization. Due to its excellent properties, such as fast swelling behavior, inter-connective porous structure, high water absorbing capacity, especially the presence of abundant carboxylmethyl groups on its backbone, the cryogel not only favored the absorption of silver ions but also was proved to be a good matrix for the incorporation of silver nanoparticles (AgNPs) by in situ chemical reduction. The structure, morphology, and swelling behavior of the cryogel and cryogel/AgNPs composite were characterized. And the results of inhibition zone test and antibacterial inhibition ratio indicated the cryogel/AgNPs composite exhibited prominent and durable antibacterial activity against Gram-negative E. coli and could be utilized as potential antibacterial materials.