Influence of surface modification of Ti6Al7Nb alloy on adhesion of poly (lactide-co-glycolide) coating (PLGA)

The paper presents the results of studies on the influence of surface topography and wettability of a Ti6Al7Nb alloy substrate on the adhesion of a PLGA coating. The alloy surface was modified using a mechanical pre-treatment including: grinding, vibration treatment, mechanical polishing, sandblasting and anodic oxidation. The polymer coating was applied to the metal substrate by a dip-coating method. The scope of the research included microscopic observations of the substrate and polymer coating using SEM and acoustic microscopy. In addition, studies on the wettability and topography of the polymer coating and the metal substrate, the thickness of the polymer coating as well as qualitative and quantitative testing of the adhesion of the polymer coating to the substrate were carried out. Coating adhesion tests were conducted for samples in the initial state and after 6 weeks exposure to Ringer's solution. Analysis of the results indicates the influence of the method used to modify the metal substrate on its topography and wettability. These parameters affect the thickness of the obtained polymer coating. Regardless the parameters of the metal substrate, a qualitative analysis of the adhesion of the coating applied to the substrate of the Ti6Al7Nb alloy did not show any delamination for both samples exposed and non-exposed to Ringer's solution. On the other hand, quantitative scratch-test studies showed different adhesion of the polymer coating to the substrate depending on the surface topography obtained by various modification methods. The cytotoxicity test conducted by the indirect method using extracts confirmed that the surface modification does not affect cell growth. The complex methods of surface pre-treatment of the alloy together with the kind of polymer selected for the study allowed to develop well adhered PLGA layers on Ti6Al7Nb intended for short term implants. The lack of delamination of the layer during 6 weeks was proved, what allows for maintaining the protection function of the layer during this period and contribute to improving biocompatibility.