Zinc-Doping Induces Evolution of Biocompatible Strontium–Calcium-Phosphate Conversion Coating on Titanium to Improve Antibacterial Property

Abstract

Implant-associated infections (IAI) remains a common and devastating complication in orthopedic surgery. To reduce the incidence of IAI, implants with intrinsic antibacterial activity have been proposed. The surface functionalization and structure optimization of metallic implants can be achieved by surface modification using the phosphate chemical conversion (PCC) technique. Zinc (Zn) has strong antibacterial behavior toward a broad-spectrum of bacteria. Herein, Zn was incorporated into strontium−calcium-phosphate (SrCaP) coatings on titanium (Ti) via PCC method, and the influence of its doping amount on the phase, microstructure, antibacterial activity, and biocompatibility of the composite coating was researched. The results indicated that traces of Zn doping produced grain refinement of SrCaP coating with no significant effect on its phase and surface properties, while a higher Zn content induced its phase and microstructure transformed into zinc−strontium-phosphate (SrZn 2 (PO 4 ) 2 ). SrCaP-Zn1 and SrCaP-Zn4 represented trace and high content Zn-doped coatings, respectively, which exhibited a similar bacterial attachment for a short time but showed inhibition of biofilm formation after continuous incubation up to 24 h. The killing rates of SrCaP-Zn1 coating for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) reached 61.25% and 55.38%, respectively. While that data increased to 83.01% and 71.28% on SrCaP-Zn4 coating due to the more-releasing Zn 2+ . Furthermore, in vitro culture of MC3T3-E1 cells proved that the Zn-doped coatings also possessed excellent biocompatibility. This study provides a new perception for the phase and microstructural optimization of phosphate coatings on implant surfaces, as well as fabricating promising coatings with excellent biocompatibility and antimicrobial properties against IAI.

Immunomodulatory biomaterials for implant-associated infections: from conventional to advanced therapeutic strategies

“…6 A Schematic image illustrating the functionalization of the orthopedic implants with Zn and its antibacterial mechanism to prevent IAI. Reproduced with permission [ 152 ]. Copyright 2022, American Chemical Society.…”

Effect of Substrates Performance on the Microstructure and Properties of Phosphate Chemical Conversion Coatings on Metal Surfaces

“…Roughness and wettability, as important properties of the material surface, are directly involved in influencing the interaction of the implanted material with the surrounding physiological environment [ 25 ]. Figure 4 a depicts the 3D profile micrographs of the ZnP coating on the TA and ZA substrates.…”

3D printed strontium–zinc-phosphate bioceramic scaffolds with multiple biological functions for bone tissue regeneration

“…Since ions released from bioceramic scaffolds play crucial roles in new bone formation, 28 the capability of SZP scaffolds for sustained release of Sr 2+ , Zn 2+ and PO 4 3À were expected to have better tissue regeneration performance and more biological functions than b-TCP scaffolds with the limited release of Ca 2+ and PO 4 3À , which was indeed proved in our following studies for the first time. Although other Sr/Zn containing biomaterials such as Sr/Zn dual ions-collagen co-assembly HA, Sr/Zn dual substituted CaP bioceramics or titanium alloy coated with Sr-Zn-P bioceramic mixture have been explored with multiple bioactivities for bone repair, [17][18][19]29 SZP scaffolds hold the advantages for clinical transformation due to the longrange ordered crystal structure of the single-phased SZP, which makes the scaffold's properties and functions super stable and sustainable. Specifically, 3D-printed SZP scaffolds exhibit multiple bioactivities including osteogenesis, angiogenesis, immunomodulation and anti-bacterial activity.…”