title: A multi-material coating containing chemically-modified apatites for combined enhanced bioactivity and reduced infection via a drop-on-demand micro-dispensing technique.
abstract: Prevention of infection and enhanced osseointegration are closely related, and required for a successful orthopaedic implant, which necessitate implant designs to consider both criteria in tandem. A multi-material coating containing 1:1 ratio of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite as the top functional layer, and hydroxyapatite as the base layer, was produced via the drop-on-demand micro-dispensing technique, as a strategic approach in the fight against infection along with the promotion of bone tissue regeneration. The homogeneous distribution of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite micro-droplets at alternate position in silicon-substituted hydroxyapatite-silver-substituted hydroxyapatite/hydroxyapatite coating delayed the exponential growth of Staphylococcus aureus for up to 24 h, and gave rise to up-regulated expression of alkaline phosphatase activity, type I collagen and osteocalcin as compared to hydroxyapatite and silver-substituted hydroxyapatite coatings. Despite containing reduced amounts of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite micro-droplets over the coated area than silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite coatings, silicon-substituted hydroxyapatite-silver-substituted hydroxyapatite/hydroxyapatite coating exhibited effective antibacterial property with enhanced bioactivity. By exhibiting good controllability of distributing silicon-substituted hydroxyapatite, silver-substituted hydroxyapatite and hydroxyapatite micro-droplets, it was demonstrated that drop-on-demand micro-dispensing technique was capable in harnessing the advantages of silver-substituted hydroxyapatite, silicon-substituted hydroxyapatite and hydroxyapatite to produce a multi-material coating along with enhanced bioactivity and reduced infection.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore.
authors.forename: Poon Nian
authors.initials: PN
authors.lastname: Lim
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore.
authors.forename: Zuyong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore.
authors.forename: Lei
authors.initials: L
authors.lastname: Chang
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore.|Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan.
authors.forename: Toshiisa
authors.initials: T
authors.lastname: Konishi
authors.affiliation: School of Materials Science and Engineering, Nanyang Technology University, 50 Nanyang Avenue, Singapore, 639 798, Singapore.
authors.forename: Cleo
authors.initials: C
authors.lastname: Choong
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Singapore, 119 757, Singapore.
authors.forename: Bow
authors.initials: B
authors.lastname: Ho
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117 576, Singapore. mpetes@nus.edu.sg.
authors.forename: Eng San
authors.initials: ES
authors.lastname: Thian
mesh_terms: D017667:Adipocytes / Q000166:cytology; D000469:Alkaline Phosphatase / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001031:Apatites / Q000737:chemistry*; D001861:Bone Regeneration; D049109:Cell Proliferation; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D003094:Collagen / Q000737:chemistry; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal; D016348:Osseointegration / Q000187:drug effects; D015675:Osteocalcin / Q000737:chemistry; D011208:Powders; D012825:Silicon / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects*; D013499:Surface Properties
chemical_list: D000900:Anti-Bacterial Agents; D001031:Apatites; D020099:Coated Materials, Biocompatible; D006882:Hydroxyapatites; D011208:Powders; D015675:Osteocalcin; D012834:Silver; D003094:Collagen; D000469:Alkaline Phosphatase; D012825:Silicon