Formation of antibacterial coatings on chitosan matrices by magnetron sputtering

Abstract

Chitosan as a biodegradable natural polymer is currently among the most attractive alternatives for the replacement of plastics, metals and other materials in various industries. Biodegradable chitosan matrices find their use as materials for biomedical devices, implants, scaffolds. Copper nanoparticles in their turn impart bacteriostatic and antibacterial properties to medical products, as well as copper coatings and nanopowders. We obtain thin copper coatings on the biodegradable chitosan matrices using magnetron sputtering. The optimal sputtering regimes were selected: high frequency discharge power of ~200 W at the frequency of 13.5 MHz in argon medium. The argon pressure was maintained within 1 Pa. As a target, a disk of 80 mm in diameter was made of copper grade M1. The resulting copper content in the samples does not exceed the toxicity threshold for humans 200–250 mg/day. The presence of an ultrathin copper film does not change the morphology and crystal structure of chitosan films. In the course of sample degradation in model media, copper is released from the film with the higher copper content in all variants of media (the highest release in the alkaline medium); and from all films in alkaline environment. The greatest yield is observed in the case of the smallest sputtering. To investigate the antimicrobial properties of copper-coated films, multiresistant strains of gram-positive and gram-negative microorganisms (S. aureus, E. coli and P. aeruginosa) were used. Summarizing the results, we can conclude that copper sputtering does not significantly affect the complex of the physicochemical properties of chitosan films, but imparts their antibacterial properties significantly; in particular, the films suppress the growth of S. aureus.