Burns can cause tremendous economic problems associated with irreparable harm to patients and their families. To characterize marine collagen peptides (MCPs) from the skin of Nile tilapia (Oreochromis niloticus), molecular weight distribution and amino acid composition of MCPs were determined, and Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical structure. Meanwhile, to evaluate the wound healing activity, in vitro and in vivo experiments were carried out. The results showed that MCPs prepared from the skin of Nile tilapia by composite enzymatic hydrolysis were composed of polypeptides with different molecular weights and the contents of polypeptides with molecular weights of less than 5 kDa accounted for 99.14%. From the amino acid composition, the majority of residues, accounting for over 58% of the total residues in MCPs, were hydrophilic. FTIR indicated that the main molecular conformations inside MCPs were random coil. In vitro scratch assay showed that there were significant effects on the scratch closure by the treatment of MCPs with the concentration of 50.0 μg/mL. In the experiments of deep partial-thickness scald wound in rabbits, MCPs could enhance the process of wound healing. Therefore, MCPs from the skin of Nile tilapia (O. niloticus) have promising applications in wound care.

Effective hemostasis is vital to reduce the pain and mortality of patients, and the research and development of hemostatic materials are prerequisite for effective hemostasis. Chitosan (CS), with good biodegradability, biocompatibility and non-toxicity, has been widely applied in bio-medicine, the chemical industry, the food industry and cosmetics. The excellent hemostatic properties of CS have been extensively studied. As a result, chitosan-based composite hemostatic materials have been emerging. In this review, the hemostatic mechanism of chitosan is briefly discussed, and then the progress of research on chitosan-based composite hemostatic materials with multiple forms such as films, sponges, hydrogels, particles and fibers are introduced. Finally, future perspectives of chitosan-based composite hemostatic materials are given. The objective of this review is to provide a reference for further research and development of effective hemostatic materials.

Three amphiphilic diblock copolymers, representative of three types of block copolymer (BCP) design, were synthesized using reversible addition-fragmentation chain-transfer (RAFT) polymerization. All of them have a same uncharged block of a random copolymer of commercially available acrylamide and acrylonitrile, P(AAm-co-AN), and exhibit a composition-tunable upper critical solution temperature (UCST). We show that by coupling a common P(AAm-co-AN) block with either hydrophobic polystyrene (PS) or hydrophilic poly(dimethylacrylamide) (PDMA) or the lower critical solution temperature (LCST) polymer of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), the BCP micelles formed in water or in phosphate buffered saline (PBS) can display diverse and UCST-dictated changes in response to temperature variations, such as the reversible dispersion-aggregation of micelles, dissolution-formation of micelles, and reversal of micelle core and corona. The results point out that P(AAm-co-AN) is a robust UCST polymer that can be introduced into controlled polymer architectures producible by RAFT, the same way as using the extensively studied LCST counterparts like poly(N-isopropylacrylamide) (PNIPAM). This ability should make the door wide open to exploring new thermosensitive polymers based on the thermosensitivity opposite to the LCST.

Chitosan oligosaccharide (COS), a natural polysaccharide with good antioxidant and anti-inflammatory properties, is the depolymerized product of chitosan possessing various biological activities. The present study was designed to investigate the possible anti-aging effect of COS on the aging model mouse induced by d-galactose (d-gal) and explore the underlying mechanism. In the experiment, 48 male Kunming mice (KM mice) were randomly divided into the normal group, model group, positive group, and low-medium-high dose polysaccharide groups (300, 600, 1200 mg/kg/day). The results showed that COS, by intragastric gavage after subcutaneous injection of d-gal (250 mg/kg/day) into the neck of mice consecutively for eight weeks, gradually recovered the body weight, the activity of daily living, and organ indices of mice, as well as effectively ameliorated the histological deterioration of the liver and kidney in mice triggered by d-gal. To be specific, COS obviously improved the activities of antioxidant enzymes in liver and kidney of KM mice, including catalase (CAT), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD), as well as decreased malondialdehyde (MDA) levels when compared with those in model group mice. Furthermore, COS not only elevated the diminished levels of serum immunoglobulin G (IgG) and IgM induced by d-gal, but also significantly inhibited the d-gal-caused upregulation of serum alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), uric acid (UA) and creatinine (CREA) levels as compared with those of mice in the model group. These results demonstrate that COS has an obvious anti-aging activity in d-gal-induced subacute aging mice, the mechanism of which, to some extent, is associated with enhancing the antioxidant defenses, reducing oxidative stress, and improving the immune function of aging model mice.

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