Enhanced biodegradability, osteogenesis, and angiogenesis of Zn-Li alloys through calcium plasma immersion ion implantation

Abstract

Biodegradable zinc alloys are a promising research focus for bone implants due to their excellent bioactivity and mechanical properties, but the slow biodegradation rate and poor osseointegration limit their clinical application. In this study, calcium (Ca) ions were implanted into the surface of Zn-0.1Li alloys to improve their biodegradable, osteogenic, and angiogenic properties via the plasma immersion ion implantation (PIII) technique. FE-SEM and AFM results have demonstrated that Ca ion implantation appropriately increased the surface micro-roughness of the Zn-0.1Li alloy, thereby providing a larger contact surface area for biodegradation and osseointegration. Analysis using AES, XRD, and XPS revealed that Ca existed in the form of CaO. Based on SRIM simulations and FIB/TEM cross-sectional analysis, the thickness of the Ca ion implantation layer is approximately 52.2 nm, with a peak implantation dose exceeding 3.5 × 10⁵ atoms/cm². Static and electrochemical corrosion tests demonstrated that Ca ion implantation significantly accelerated the overall degradation behaviour of the Zn-0.1Li alloy and the release of zinc ions. In vitro experiments using MC3T3-E1 cells and HUVECs showed that Ca ion implantation samples significantly increased the expression of osteogenic genes (ALP, Runx2, OCN, and Col I) and angiogenic genes (VEGF, eNOS, and FGFR), demonstrating superior osteoinductive and angiogenic properties. Finally, in vivo rat femoral implantation studies revealed that Ca ion implantation samples exhibited enhanced biodegradation and osseointegration. In conclusion, Ca ion implantation effectively improved various properties of the Zn-0.1Li alloy, broadening its potential applications in dental and orthopedic fields.

Statement of significance

Zn alloys are one of the most promising biodegradable metals and have become a research hotspot in dentistry and orthopedics. However, the slow biodegradation rate and poor osteoinductivity severely limit their clinical application. In this study, we implanted Ca ions into the surface of Zn-0.1Li alloys via PIII to modulate their properties. In vitro and in vivo studies have confirmed that Ca ion implantation can effectively improve the surface micromorphology, biodegradability, osteoinductivity and angiogenic properties of Zn-0.1Li alloys, making them more prospective for use in bone implants.