In vitro biocompatibility investigation of femtosecond laser surface modified high entropy TiTaHfNbZr alloy as a potential biomaterial for orthopedic applications

Abstract

This study aims to evaluate the biocompatibility of a novel, biomedically promising TiTaHfNbZr high entropy alloy (HEA) for orthopedic implant applications and evaluates the biocompatibility enhancements via femtosecond laser-induced surface patterning. With this purpose, four different surface patterns with grooves and indents of varying repeating frequencies were formed on the TiTaHfNbZr surfaces via laser processing, followed by comprehensive in vitro biocompatibility tests. Results demonstrated that laser patterning is a highly effective strategy for enhancing the biocompatibility of TiTaHfNbZr. The inherent biocompatibility of the HEA, superior to that of 316L stainless steel (SS), is attributed to its composition of exclusively non-cytotoxic elements. Laser-induced surface modifications further amplified this advantage by increasing surface roughness and hydrophilicity, which directly promoted Saos-2 osteoblast adhesion and proliferation. Among the formed patterns, the narrow-spaced groove (HEA-2) pattern emerged as the optimal topography, promoting cell alignment and yielding the highest cell densities. The anisotropic nature of this pattern, combined with its high surface energy, was identified as the primary mechanism for its distinct performance. Consequently, laser-patterned TiTaHfNbZr HEA represents a class of highly promising material for next-generation orthopedic implants. The unique synergistic effect of the biocompatible high-entropy matrix and the laser-induced surface topography provides a clear pathway to accelerate early-stage osseointegration, establishing a compelling rationale for subsequent in vivo studies to evaluate long-term clinical applicability.