Formation of three-dimensional polymer structures through radical and ionic reactions of peroxychitosan

Abstract Chitosan (Chit) and its derivatives have received much attention due to their biodegradability, non-toxicity, and biocompatibility along with their antimicrobial, antiviral, and antitumoral activity. The preparation of three-dimensional chitosan-based polymer structures is usually conducted through the formation of ionic, covalent, and hydrogen bonds or hydrophobic interactions using chemical intermolecular cross-linking. The objective of this work is to provide a systematic review of recent studies by various research groups on three-dimensional polymer chitosan structures for biomedical applications, drug delivery, cosmetics. The introduction of a peroxide –OO– group into the chitosan macromolecule, achieved by the authors of this review, allows for the formation of three-dimensional structures of chitosan derivatives through radical and ionic mechanisms. To the best of our knowledge, there is no information in the literature on peroxide derivatives of Chit synthesized through the reactions of the amino group other than the above-mentioned works. Radical reactions were initiated by a controlled decomposition of the peroxide groups in peroxychitosans (PChit) in order to form a three-dimensional polymer matrix. PChit were synthesized by the method of polymer-analogous reaction through the peroxidation of chitosan with tert-butylperoxymethyl maleate. pH-sensitive macrohydrogels with a covalently cross-linked three-dimensional polymer matrix were developed by graft copolymerization of 1-vinyl-2-pyrrolidone and PChit in an aqueous medium. The pH-sensitive macrogels absorb and release an antibiotic cefazolin depending on pH and can be grafted to a cotton fabric. pH-sensitive spherical hydrogel nanoparticles were synthesized in aqueous nanodroplets of a reverse emulsion via free-radical graft copolymerization of 1-vinyl-2-pyrrolidone and PChit with primary-tertiary peroxide groups. The formed nanogels were loaded with anionic or cationic fluorescent dyes as drug models. The swelling and release profiles depend on polymer-network density, nature of the dye, and pH. Peroxychitosan was synthesized through the radical interaction between chitosan and a peroxide monomer followed by the emulsion polymerization of vinyl monomers in the presence of peroxychitosan. Self-assembled pH-sensitive submicron particles were formed due to the intermolecular electrostatic interaction between the ammonium groups of chitosan and the carboxylate groups of peroxide-containing oligooxyethylene pyromellitate (OOP). The particles have the structure of an ionically cross-linked hydrogel, their size and surface charge depending on pH and the ratio of the functional groups. The presence of the OOP peroxide groups allowed for further synthesis of covalently cross-linked pH-sensitive nanoparticles. The three-dimensional polymer structures of chitosan and its derivatives are promising candidates for the development of polymer drug-delivery systems, cosmetics, antibacterial coatings.