Functionalizing Orthopedic Implants with Silver Nanoparticles to Treat Infection

INTRODUCTION Implant-associated infection, although rare, has been one of main complications accompanied by orthopedic implant surgeries including prosthetic joint replacement and fracture fixation. The number of such infections has continuously increased with growing demands for surgical implantation due to population aging and increased participation in outdoor activities. The established infections may not be effectively treated with systemic chemotherapy with antibiotics, often necessitating additional surgical procedures such as simple debridement and reimplantation. Even for systemic antibiotic treatment, there still remain several concerns, for example, systemic toxicity, low efficiency and hospitalization issue. Therefore, there have been continuing need to deliver antibacterial agent to the surgical site in a sustained manner. Calcium phosphate (CaP) biomaterials including hydroxyapatite (HAP), β-tricalcium phosphate (β-TCP) and biphasic calcium phosphate (BCP) composed of HAP and β-TCP, are widely used as a bone substitute and a coating material on various orthopedic implants. On the other hand, silver ions have demonstrated broad antibacterial spectrum including gram-positive and gram-negative pathogens. In view of clinical relevance of CaP materials and well-known antibacterial activity of silver, we hypothesized that the silver ions gradually released from CaP-based orthopedic implants would efficiently suppress postsurgical infections. Here, we present a facile method to grow antibacterial silver particles on CaP biomaterials and subsequently release silver ions for a controllable period of time. Our strategy includes two steps; i) binding a reducing agent, citrate, on CaP surface and ii) reducing silver ions (Ag) into silver (Ag) locally on the CaP surface. Our goal in this study is the formation of silver particles on CaP-based biomaterials and the sustained release of silver ions with controllable dosage.