Synthesis of N,N-Diethyl, N-Methyl Chitosan Chloride with Certain Quaternization Degree and Molecular Spectroscopic and Thermo-Morphological Study of the Alkylation

Recent advances in chitosan-based materials; The synthesis, modifications and biomedical applications

The attention to polymer-based biomaterials, for instance, chitosan and its derivatives, as well as the techniques for using them in numerous scientific domains, is continuously rising. Chitosan is a decomposable naturally occurring polymeric material that is mostly obtained from seafood waste. Because of its special ecofriendly, biocompatible, non- toxic nature as well as antimicrobial properties, chitosan-based materials have received a lot of interest in the field of biomedical applications. The reactivity of chitosan is mainly because of the amino and hydroxyl groups in its composition, which makes it further fascinating for various uses, including biosensing, textile finishing, antimicrobial wound dressing, tissue engineering, bioimaging, gene, DNA and drug delivery and as a coating material for medical implants. This study is an overview of the different types of chitosan-based materials which now a days have been fabricated by applying different techniques and modifications that include etherification, esterification, crosslinking, graft copolymerization and o-acetylation etc. for hydroxyl groups' processes and acetylation, quaternization, Schiff's base reaction, and grafting for amino groups' reactions. Furthermore, this overview summarizes the literature from recent years related to the important applications of chitosan-based materials (i.e., thin films, nanocomposites or nanoparticles, sponges and hydrogels) in different biomedical applications.

Recent advances of chitosan-based polymers in biomedical applications and environmental protection

Interest in polymer-based biomaterials such as chitosan and its modifications and also the methods of their application in various fields of science is uninterruptedly growing. Owing to unique physicochemical, biological, ecological, physiological properties, such as biocompatibility, biodegradability, stability in the natural environment, non-toxicity, high biological activity, economic affordability, chelating of metal ions, high sorption properties, chitosan is used in various biomedical and industrial processes. The reactivity of the amino and hydroxyl groups in the structure makes it more interesting for diverse applications in drug delivery, tissue engineering, wound healing, regenerative medicine, blood anticoagulation and bone, tendon or blood vessel engineering, dentistry, biotechnology, biosensing, cosmetics, water treatment, agriculture. Taking into account the current situation in the world with COVID-19 and other viruses, chitosan is also active in the form of a vaccine system, it can deliver antibodies to the nasal mucosa and load gene drugs that prevent or disrupt the replication of viral DNA/RNA, and deliver them to infected cells. The presented article is an overview of the nowaday state of the application of chitosan, based on literature of recent years, showing importance of fundamental and applied studies aimed to expand application of chitosan-based polymers in many fields of science.

Encapsulation and <i>In Vitro </i>Controlled Release of Doxycycline in Temperature-Sensitive Hydrogel Composed of Polyethyleneglycol–polypeptide (L-Alanine-co-L-Aspartate)

Doxycycline was loaded with synthesized micelles composed of methyl Poly (ethylene glycol-block-poly (L-alanine–co–L-aspartate), or mPEG–Ala–Asp, and then characterized as a drug delivery carrier. The synthesis of the temperature-sensitive mPEG–Ala–Asp block copolymer was carried out by two-step ring-opening polymerization: firstly, the mPEG reacts with L-alanine N-carboxylic anhydride, and secondly the resulting mPEG–Ala reacts with benzyl aspartate N-carboxylic anhydride. The molecular structure of the copolymers obtained was determined by FT-IR and NMR spectroscopy methods and the micelles were characterized by SEM, TEM and DLS, respectively. The controlled release of Dox from hydrogel in the presence of PBS (8 to 9% by weight) lasts 6 to 7 days exhibiting stable release rates. The drug release mechanisms were studied: Higuchi and zero order models. The results and correlation coefficients applied to the Higuchi and zero-order models. The findings show the potential use of mPEG–Ala–Asp as an effective depot matrix to deliver anthracycline class drugs.