Infection resistant polymer brush coating on the surface of biodegradable polyester

Biomaterials with anti-infective coatings are usually found to suffer from low cyto-compatibility and therefore, development of a stable, effective polymeric anti-bacterial substrate without compromising the biocompatibility is still an unmet challenge. Addressing this, a simple strategy for developing non-leaching antibacterial coating on a biodegradable substrate is reported here. The strategy can be utilized for mitigating serious biomedical implant related complications arising from generation of biocide resistant bacterial strains, losing antibacterial activity over time etc. without significantly compromising the cytocompatibility of the biomaterials. To develop the infection resistant yet cytocompatible biomaterials comprised of tartaric acid based biodegradable aliphatic polyester, we have primarily focussed on attaching anti-infective polymer brushes such as poly (2-hydroxyethyl methacrylate) (PHEMA), poly (poly (ethylene glycol) methacrylate) (PPEGMA) and poly[(2-methacryloyloxyethyl] trimethyl ammonium chloride) (PMETA) on hydroxyl functionalized polyester substrate via surface initiated atom transfer radical polymerization (SIATRP). The brushes were thoroughly characterized for reaction kinetics, grafting yield, surface density, topography and hydrophilicity. Among the various brushes, cationic polymer brush (PMETA) was found to exhibit highest antibacterial activity, with only ~3% and ~4% adherence of E. coli (Escherichia coli) and S. aureus (Staphylococcus aureus), respectively. In order to show its widespread use and also to vary initiator density, polylactic acid (PLA) was blended with this tartaric acid based aliphatic polyester and a 3D (three-dimensional) scaffold was fabricated by 3D printing using the blend. Finally, PMETA brush was grown onto the scaffold surface for various time periods and the evaluation of antibacterial activity (using gram positive and gram-negative bacteria) and cytocompatibility (using mammalian osteoblast cells) were carried out on the brush modified scaffold. A balance between antibacterial activity and cytocompatibility was found at optimum brush length achieved after 18 h of SIATRP suggesting that this composition offers a stable, non-leaching, anti-infective, but cytocompatible coating on biodegradable polymeric implant surface for addressing several biomaterials associated infections.