Here, a novel macroporous hydrogel dressing is presented that can accelerate wound healing and guard against bacteria-associated wound infection. Carboxymethyl agarose (CMA) is successfully prepared from agarose. The CMA molecular chains are cross-linked by hydrogen bonding to form a supramolecular hydrogel, and the hydroxy groups in the CMA molecules complex with Ag + to promote hydrogel formation. This hydrogel composite exhibits pH-responsiveness and temperature-responsiveness and releases Ag + , an antibacterial agent, over a prolonged period of time. Moreover, this hydrogel exhibits outstanding cytocompatibility and hemocompatibility. In vitro and in vivo investigations demonstrate that the hydrogel has enhanced antibacterial and anti-inflammatory capabilities and can significantly accelerate skin tissue regeneration and wound closure. Astonishingly, the hydrogel can cause the inflammation process to occur earlier and for a shorter amount of time than in a normal process. Given its excellent antibacterial, anti-inflammatory, and physicochemical properties, the broad application of this hydrogel in bacteriaassociated wound management is anticipated.

Natural deep eutectic solvents (NADESs) are sustainable, nontoxic, and biodegradable solvents, which are composed of natural primary metabolites. A green and efficient approach based on choline chloride−malic acid, a NADES, was developed for extracting chitin from crustacean shells, and its effectiveness for demineralization and deproteinization was determined. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to investigate changes in the chemical composition of extracted chitin. The results revealed that most of the minerals and proteins were removed from the shrimp shells by using a NADES with the assistance of microwave irradiation. The quality of the obtained chitin was superior, and it displayed a relative crystallinity of 71%. All of these results were achieved without using harsh chemicals, which can raise environmental issues. This study provides a green and facile approach for chitin production from crustacean shells and reveals the potential of NADESs for applications in the extraction of biopolymers from natural sources.

In this study, a novel biocompatible magnetic chitin nanofiber composite (MCNC) was developed as a support for enzyme immobilization, and the enzyme-immobilizing ability was elucidated using chymotrypsin (CT) as a model enzyme. Chitin nanofibers (CNFs) were prepared via 2,2,6,6tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of chitin and then further modified with magnetic nanoparticles. Glutaraldehyde was used to crosslink the additional CT molecules and aggregate them onto the MCNCs. The CNFs were characterized by transmission electron microscopy, and Fourier transform infrared spectroscopy. The results showed that the CNFs were properly formed and that the CT molecules immobilized on the MCNCs presented excellent properties. After heating the composites at 60 °C for 3 h, the non-crosslinked and cross-linked immobilized CTs retained 51.6% and 70.7% of the initial activity, respectively, whereas the free CTs retained only 29.6% of the initial activity. In addition, non-cross-linked and cross-linked immobilized CTs retained 85.7% and 84.9% of the initial activity, respectively, after 20 days, whereas the free CTs retained only 18.8% of the initial activity. When the MCNCs were used to immobilize the CT molecules, the enzyme loading capacity was enhanced up to 6.3-fold upon cross-linking. Moreover, the immobilized CTs could be easily separated and recycled from the reaction system by a magnetic force.

In this research, a two-step extraction approach was developed for chitin preparation from shrimp shells by utilizing citric acids and deep eutectic solvents (DESs), which effectively removed minerals and proteins. In the first step, minerals of shrimp shells were removed by citric acid, and the demineralization efficiency reached more than 98%. In the second step, the removal of protein was carried out using deep eutectic solvents with the assistance of microwave, and the deproteinization efficiency was more than 88%. The results of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA) showed that the quality of DES-prepared chitin was comparable to that of traditional acid/alkali-prepared chitin. These results were realized without utilizing hazardous chemicals, which are detrimental to the environment. This research indicates that a DES-based preparation approach has the potential for application in the recovery of biopolymers from natural resources.

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