HiPIMS carbon coatings show covalent protein binding that imparts enhanced hemocompatibility

Magnetron sputtering is an established coating process rarely used for carbon films due to low deposition rates and poor adhesion. Substantial ion fluxes with tunable energies can be added by converting the process to high power impulse magnetron sputtering (HiPIMS) using a high voltage pulsed power supply. Here, we use a mixed mode (HiPIMS with transition to arc) process to deposit carbon coatings for applications in blood-contacting devices. Films produced at negative substrate bias in the range 0-350 V covalently bind protein molecules directly from buffer solution, making them biologically functionalisable, unlike coatings deposited with conventional magnetron sputtering. The HiPIMS coatings showed strikingly low thrombogenicity. A proof of principle application was demonstrated by deposition onto a stainless steel cardiovascular stent. Adhesion and toughness sufficient to withstand the extreme deformation, that accompanies surgical insertion, was achieved with negative bias in the range 100-350 V. Covalently immobilized, cell-adhesive extracellular matrix (ECM) proteins, tropoelastin and fibronectin, significantly increased the proliferation of endothelial cells on the HiPIMS coatings. Optimum proliferation was observed in the negative bias range 200-350 V. These results suggest that HiPIMS carbon coatings have great potential for biomedical devices where functionalization with active biomolecules can accelerate tissue integration. (C) 2018 Elsevier Ltd. All rights reserved.