The Controllable Release Of La³⁺ In SiO₂/Ca-P Gradient Rare-earth Coating Fabricated By Laser Cladding And Its Inhibitory Effect On Osteoclast Activity

Aseptic loosening is the main reason for joint failure after artificial implantation,and osteolysis?wear debris disease?is the primary factor of aseptic loosening.Rare earth ion with the function of inhibiting the formation of osteoclast is an effective way to prevent osteolysis,however,there is a limitation in applying rare earth therapy due to its concentration-dependent behaviors.How to effectively control the concentration of rare earth ions around the joint becomes a huge challenge.In this paper,a good solution to this challenge is that the calcium-phosphate bioceramic coating doped with La₂O₃ and SiO₂ was fabricated using gradient design by laser cladding on medical metal material?Ti-6Al-4V?.The structure and performance of ceramic coatings were continuously optimized by adjusting the the doping amount of SiO₂ and calcium-phosphorus ratio.XRD analysis confirms that when the doping amount of SiO₂ is 10wt%,the formation amount of HA+TCP by laser cladding reaches the maximum.Analysis of the coating cross section shows that the doping of SiO₂ improves the bonding quality of the bioceramic coating.In particular,when the doping amount of SiO₂ is 10 wt%,the cracks between the coating and the substrate significantly reduce,and at the same time,the microhardness distribution and the average microhardness of the ceramic layer,alloying layer and substrate are more uniform compared with other coatings.Bioactivity analysis shows that the coating with Ca/P=1.40 and 10 wt%SiO₂ is of excellent ability to deposit bone-like apatite,determining the best bioactivity of the coating.Biocompatibility analysis shows that the Ca-P ceramic coating doped with La₂O₃ and SiO₂ does not express cytotoxic,and when the doping amount of SiO₂ is 10wt%,the Ca/P ratio is 1.40,it shows the best biocompatibility of osteoblasts.The degradation of Ca-P coating and the release of La³⁺were estimated by immersing the coating in SBF solution.Results show that the weight of the coating alternates with the continuous deposition of bone-like apatite and the degradation of TCP.The release amount of La³⁺exhibits fluctuating changes.The average concentration of La³⁺in undoped SiO₂ coating fluctuates between 9.5 PBB and 12.0PPB per day.The concentration of La³⁺in doped SiO₂ coating averages 1.4?5.7 PBB per day.