Surface modification of PLLA scaffolds via reactive magnetron sputtering in mixtures of nitrogen with noble gases for higher cell adhesion and proliferation

Abstract

Despite the widespread use of bioresorbable electrospun poly-L-lactic acid scaffolds in tissue engineering, a significant drawback is the high hydrophobicity of their surface. A proper solution for this problem is the surface modification with titanium oxynitride coatings using reactive magnetron sputtering. However, this method is characterized by a low deposition rate and the difficult selection of suitable working parameters. A feasible solution to this problem is the addition of a noble gas to the working gas nitrogen, which increases the deposition rate and thus the coating thicknesses, even with gentle magnetron sputtering process parameters. In this study, the results of surface modification of poly-L-lactic acid scaffolds using direct current reactive magnetron sputtering of a titanium target in the presence of a mixture of the working gas nitrogen with one of the following noble gases: helium, neon, argon, krypton, and xenon. Due to this modification, depending on the composition of the gas mixture, a thin nitrogen-containing titanium coating forms on the scaffold surface, represented by titanium oxide and titanium oxynitrides of different stoichiometry. At the same time, the modification process does not significantly affect the morphology, crystallinity and molecular conformation of the poly-L-lactic acid scaffold backbones, while an increase in the surface wettability is observed. Another biomedical important effect of this surface modification is an observed increase in the adhesion and proliferative activity of fibroblast culture applied to the investigated poly-L-lactic acid scaffold samples. The poly-L-lactic acid scaffold samples surface-modified via direct current reactive magnetron sputtering of a titanium target in a mixture of the working gas nitrogen and the noble gas argon shows the highest number of adhered fibroblasts.