title: Proposed mechanism of antibacterial action of chemically modified apatite for reduced bone infection.
abstract: Surface-bound silver ions were demonstrated to be responsible for the antibacterial action of silver, silicon-containing hydroxyapatite (Ag,Si-HA). X-ray photoelectron spectroscopy, transmission electron microscopy, and induced coupled plasma spectroscopy results suggested that silver ions in the crystal structure diffused toward the crystal surface of Ag,Si-HA, and interacted with adherent Staphylococcus aureus bacteria, thus damaging the cell wall and inducing leakage of potassium ions. All these steps constitute the mechanism of antibacterial action for Ag,Si-HA. Consequently, Ag,Si-HA gave rise to a 7-log reduction of the adherent bacteria as compared to HA and Si-HA at 168 h. Silicon in Ag,Si-HA helped to mitigate the reduced effect of bone differentiation in Ag-HA as shown in the alkaline phosphatase, type I collagen and osteocalcin results, promoting enhanced biological response, without compromising the antibacterial property. On the whole, Ag,Si-HA containing an optimized content of 0.5 wt % silver and 0.7 wt % silicon provides antibacterial properties and enhanced biological response.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117 576, Singapore.
authors.forename: P N
authors.initials: PN
authors.lastname: Lim
authors.forename: L
authors.initials: L
authors.lastname: Chang
authors.forename: B Y
authors.initials: BY
authors.lastname: Tay
authors.forename: V
authors.initials: V
authors.lastname: Guneta
authors.forename: C
authors.initials: C
authors.lastname: Choong
authors.forename: B
authors.initials: B
authors.lastname: Ho
authors.forename: E S
authors.initials: ES
authors.lastname: Thian
mesh_terms: D000273:Adipose Tissue / Q000166:cytology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001031:Apatites / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects / Q000382:microbiology* / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D007477:Ions; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D056951:Photoelectron Spectroscopy; D011188:Potassium / Q000737:chemistry; D012825:Silicon / Q000494:pharmacology; D012834:Silver / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000648:ultrastructure; D013499:Surface Properties
chemical_list: D000900:Anti-Bacterial Agents; D001031:Apatites; D007477:Ions; D012834:Silver; D011188:Potassium; D012825:Silicon
keywords: antibacterial; apatite; silicon; silver; stem cell