Interplay between zinc surface functionalization and degradation behavior in targeted implant applications

Zinc (Zn) is a promising biodegradable metal with an optimal degradation rate and biocompatible degradation products. Zn has been widely studied in transient bone healing and cardiovascular stent applications, with research suggesting potential neurovascular and gastrointestinal applications. Therefore, understanding Zn's behaviour across these physiological environments is crucial for guiding further research. Advances in additive manufacturing allow exploring Zn's topography and porosity, while surface functionalisation is key to enhancing Zn's bioactivity and drug-eluting, creating opportunities tailored to patient needs. Surface modifications of bioresorbable Zn can significantly influence its degradation behaviour and corrosion layer composition. Current research highlights various modifications, with ZnO coatings showing variable behaviour, phosphates generally slow corrosion, and polymers having minimal impact on Zn degradation. This paper comprehensively analyses in vitro and in vivo models for Zn degradation, exploring how surface modifications influence this profile. It also synthesises biological data on degradation products and their biological effects. A thorough understanding of Zn degradation and its biological interactions is essential as biomaterials evolve from passive to smart replacements, highlighting key challenges and future directions in this evolving field.