Formation of the octadecylphosphonic acid layer on the surface of Ti6Al4V ELI titanium alloy and analysis using Raman spectroscopy

Abstract

Increasing life expectancy, a sedentary lifestyle and bone diseases all contribute to an increasing demand for endoprostheses. Currently, the service life of a knee prosthesis is 10-17 years on average, depending on the patient's weight and activity. In addition, the most common reasons for revision operations after implantation are prosthesis loosening and infections resulting from the lack of implant-bone connection. That is why it is so important to constantly search for new materials or improve the current methods of obtaining biomaterials and modifying their surfaces. The main goal of the research is to improve the bonding of hydroxyapatite (HA) on the surface of titanium alloy, which is used in the construction of endoprostheses. At this stage of the research, octadecylphosphonic acid (ODPA) deposited on the surface of the Ti6Al4V ELI alloy was analyzed. To verify the layer, HA attachment (the precipitation process) was first checked, and then the modified plates were immersed in a synthetic body fluid (SBF) to simulate the conditions in the living organism. At each stage of the study, the samples were analyzed using: SEM, EDS and Raman spectroscopy - spectral measurements and surface mapping were performed. The study were supplemented by the measurements of the contact angle - checking the wettability of the surface, which is important for the analysis of biomaterials and surface roughness measurements by confocal microscopy. The results shows that ODPA it increases the amount of precipitation of HA when dipped in SBF. Another interesting finding is that the addition of ODPA to the annealed titanium alloy restricts the precipitation of HA on its surface.

Keywords: Endoprosthesis; Hydroxyapatite; ODPA; Raman spectroscopy; SBF; Titanium alloy.