Synthesis; characterization and antimicrobial effects of composites based on multi-substituted hydroxyapatite and silver nanoparticles

Abstract

Nano hydroxyapatite doped with zinc (0.2wt%), silver (0.25wt%) and gold (0.025wt%), (HAP), has been obtained by an innovative wet chemical approach, coupled with a reduction process for silver and gold. The synthesized multi-substituted nano HAP was freeze-dried and calcined at 650°C. Nano HAP has been characterized by XRD, FTIR spectroscopy and imaging techniques: TEM, SEM and AFM. Then, nano HAP was mixed with previously synthesized silver nanoparticles (AgNPs), in the amount of 9wt%, to give a novel material (HAP-Ag). The AgNPs were prepared by the reduction of silver nitrate with glucose in alkaline medium. TEM and UV–Vis confirmed the formation of AgNPs with an average size of 12nm. Further, organic matrix composites were obtained from a filler made of HAP and/or HAP-Ag and a mixture of monomers (such as bis-GMA and TEG-DMA), which were polymerized at various compositions in AgNPs content up to 5.4wt%. Antibacterial activities of these composites were investigated against several different pathogenic species: Escherichia coli, Staphylococcus aureus, Staphylococcus spp., Bacillus cereus, and Candida albicans, using the Kirby–Bauer disk-diffusion method. Antibacterial activities are enhanced with increasing of silver content within composites. These effects clearly reveal that AgNPs can be effectively utilized in combination with multi-substituted HAP and polymeric matrix, both used as carriers, in order to improve their efficiency against various pathogenic species. These composites can be considered a promising antimicrobial material for coating of orthopedic and dental implants or used as bone cements in surgical applications.