Covalent Grafting of Chitosan on Plasma-Treated Polytetrafluoroethylene Surfaces for Biomedical Applications

Surface modification of polymeric materials allows to improve the biomaterial surface properties, enabling the development of optimized materials that have mechanical and biological responses adapted or adaptable to the environment where they will be implanted. Chitosan is claimed as a biopolymer with biodegradable, biocompatible and antimicrobial properties making it particularly interesting for the development and application of new functionalized materials. However, its properties and applications strongly depend on its degree of deacetylation (DDA) and molecular weight (Mw). In this study, three types of chitosan were used and fully characterized according to their DDA and Mw by ¹³C NMR, FTIR, potentiometric titration and SEC. Then, three linking arms were investigated in order to graft these three chitosan types on aminated PTFE surfaces: glutaric anhydride, poly(ethylene glycol) bis(carboxymethyl) ether and poly(ethylene-alt-maleic anhydride). The grafting efficiencies were evidenced by XPS, with an increase of chitosan characteristic bands in high resolution spectra, and by contact angle measurements, which indicated the hydrophilic character of the surfaces. Topographic changes after grafting were also observed by SEM with evidences of the grafting procedure influence. Results show the potential of conjugating plasma treatments with grafting techniques towards the development of optimized chitosan-based coatings for a wide range of applications in biomaterials and materials for health.