Development of Ti–Ta–Nb–Mo–Zr high entropy alloy by μ-plasma arc additive manufacturing process for knee implant applications and its biocompatibility evaluation

Abstract

It describes development of equiatomic Ti–Ta–Nb–Mo–Zr HEA by μ-plasma arc additive manufacturing process for knee implant applications, its microstructure study and in-vitro biocompatibility evaluation using cell viability, released metallic ions, and corrosion behaviour. Cell viability was evaluated by treating HeLa, HEK-293, and BHK cells with 20, 40, 60, and 100 μl concentrations of prepared media for the developed HEA for 24, 48, 72 h incubation durations. Released amounts of Ti, Ta, Nb, Mo, and Zr ions were estimated in 4.4; 5.4; and 7.4 pH value simulated body fluid solution (SBF) for immersion durations of 1, 3, and 7 weeks. Corrosion behaviour was studied in 4.4; 5.4; and 7.4 pH value SBF solution at 37 °C. Ti–Ta–Nb–Mo–Zr HEA consists of BCC major and minor phases having fine dendritic and inter-dendritic structure. Average % cell viability decreased with increase in prepared media concentration. Overall average values of viability for HeLa, HEK-293, and BHK cells treated with prepared media are 90%; 88%; and 92% respectively. BHK cells showed maximum cell viability at each media concentration and for each incubation duration. Ti–Ta–Nb–Mo–Zr HEA did not harm appearance of HeLa, HEK-293, and BHK cells. Overall averaged released amounts of Ti, Ta, Nb, Mo, and Zr ions are 37, 26; 57; 38, and 28 ppb respectively. Ti–Ta–Nb–Mo–Zr HEA has minimum values of all essential corrosion parameters without causing any pitting. It showed excellent biocompatibility hence referred as bio-HEA which is a new class of biomaterials for knee implants that can overcome limitations of the present materials.