Zinc as a potential bio-degradable temporary implant material

Abstract

This paper discusses the possibility of developing metallic zinc (Zn) and its alloys as temporary bio-implants by improving its properties through alloying, mechanical deformations and surface modifications. Even though the research on Mg and Fe as potential temporary implant materials started over two decades ago, Zn is a comparatively newer candidate in this arena. The scope for Zn-based materials for bio-related applications is immense due to their metabolically essential status, ideal biodegradation rates and the possibility of proper excretion by the kidneys. This paper covers the unique favourable properties of Zn and its alloys, which can be explored for bio-applications, along with its limitations and possible options to overcome the limitations. The mechanical properties of Zn implants can be improved to the set standards of load-bearing applications by alloying and mechanical deformations like extrusion, rolling and severe plastic deformations. As a result, the microstructure of the metal alters by grain refinement, formation and redistribution of intermetallic phases, resulting in enhanced hardness, Young's modulus and elastic modulus of the material. The Zn implant surface can be made fully bioactive and corrosion-resistant by engineering its surfaces with biocompatible polymers, bioactive materials like hydroxyapatite and bio-inductive elements like Si. The biochemical treatments, sol–gel techniques and plasma electrolytic oxidation (PEO) processes are effective for surface modification of Zn-based materials. Alloying, mechanical treatments and surface modification techniques are reported to be effective in improving the function of Zn-based implant materials, as discussed in this paper.