Modification of chitosan using amino acids for wound healing purposes: A review.

Chitosan, a well-known biopolymer due to its unique properties, has received considerable attention as a result of the amine group activity that locates on the backbone of chitosan. To improve the mechanical and antibacterial characteristics of chitosan, various modifications have been used. Amino acids, the monomeric units of proteins, among all other compounds have been chosen to discuss as promising materials for wound healing in combination with chitosan. This review aims to provide an up-to-date overview of the methods used for modification of chitosan and the potential biomedical application, in particular wound healing, reported in the literature during the last five years.

Preparation of chitosan-based composites with urethane cross linkage and evaluation of their properties for using as wound healing dressing.

In this research, biocomposite films containing chitosan (CS), polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), with different ratios, have been provided. The effects of adding hexamethylene 1, 6-di(aminocarboxysulfonate) (HMDACS) as cross-linking agent and the formation of urethane linkage on mechanical properties such as tensile strength, elongation and dynamic-mechanical properties such as storage modulus and tan δ were studied. Also, the antibacterial properties of the composites were investigated by viable bacterial cell counting and compared in reducing the bacterial growth. The final results showed the composite containing CS (50 wt%), PVA (30 wt%), PVP (20 wt%) and HMDACS (2 wt%) had the highest mechanical properties. Scanning electron microscopy (SEM) micrographs confirmed uniform distribution of components in the polymer matrix. In general, low contact angle values revealed the hydrophilicity of the prepared films. It was found that the composites made by combining CS, PVA and PVP at concentration of 50, 25, 25 wt% (A3) and 60, 20, 20 wt% (B4), cross-linked with 2 wt% HMDACS, had the best antibacterial activity against Escherichia coli and Staphylococcus aureus, hence they can be used as promising materials for the preparation of wound dressings.

Ciprofloxacin-functionalized magnetic silica nanoparticles: as a reusable catalyst for the synthesis of 1H-chromeno[2,3-d]pyrimidine-5-carboxamides and imidazo[1,2-a]pyridines.

In this research, synthesis and characterization of new surface-functionalized magnetic silica nanoparticles are reported. The magnetic silica nanoparticle was synthesized by a silica coating of the magnetite nanoparticles through a sol-gel process, and then, their surface was modified by (3-chloropropyl)triethoxysilane and covalently functionalized by ciprofloxacin. The catalyst activity of prepared functionalized nanoparticle was investigated by isocyanide-based multicomponent reactions for the synthesis of 1H-chromeno[2,3-d]pyrimidine-5-carboxamides and imidazo[1,2-a]pyridines. This catalyst was recycled by magnetic filtration and reprocessed five times without having a significant loss of catalytic activity.