Influence of the pre-exposure of a Zn-0.8Mg-0.2Sr absorbable alloy in bovine serum albumin containing media on its surface changes and their impact on the cytocompatibility of the material

In this study, the ternary alloy ZnMg0.8Sr0.2 (wt%) was pre-exposed in a phosphate buffer solution (PBS) with and without the addition of 1 wt% of bovine serum albumin (BSA) to simulate the early stage of the post-implantation period. We investigated the influence of the presence of BSA in the pre-exposure medium on surface chemistry, roughness topography and cytotoxicity of the pre-exposed materials. This study revealed that the pre-exposure in PBS with the addition of BSA induces the formation of a relatively thick and compact phosphate layer on the sample surface. In contrast, the majority of the surface of the samples pre-exposed in pure PBS appear almost untouched, and only a few small areas covered by eye-visible corrosion products were observed. This resulted in lower ion release (66 µmol/L) and a consequent decrease of the cytotoxicity of the eluates prepared from the samples pre-exposed in the BSA containing media. Together with the knowledge available from the literature, the obtained results indicate that BSA affects the degradation mechanism of the Zn-based alloy, resulting in the formation of zinc-BSA complexes. These complexes stimulate the precipitation of phosphates and a consequent formation of solid corrosion products with a protective function. This partially mimics the surface changes occurring in the early post-implantation period. The aforementioned suggests that a suitable pre-exposure of Zn-based absorbable materials in a protein containing media could be used as an approach to obtain reliable data about cytocompatibility by in vitro tests and reduce the discrepancies with the results obtained in vivo.