Synthesis and Antibacterial Evaluation of Calcinated Ag-Doped Nano-Hydroxyapatite with Dispersibility

Abstract

Purpose

Dispersible hydroxyapatite (HAp) nanoparticles are very useful for applying a monolayer to implantable medical devices using the nano-coating technique. To improve tolerance to infection on implanted medical devices, silver-doped HAp (Ag-HAp) nanoparticles with dispersiblity and crystallinity were synthesized, avoiding calcination-induced sintering, and evaluated for antibacterial activity.

Methods

The Ca_10-xAg_x(PO₄)₆(OH)₂ with x = 0 and 0.2 were prepared by wet chemical processing at 100°C. Before calcination at 700°C for 2 h, two kinds of anti-sintering agents, namely a Ca(NO₃)₂ (Ca salt) and a poly-acrylic acid/Ca salt mixture (PAA-Ca), were used. Escherichia coli was used to evaluate the antibacterial activity of the nanopowder.

Results

When PAA-Ca was used as an anti-sintering agent in calcination to prepare the dispersible nanoparticles, strong metallic Ag peaks were observed at 38.1° and 44.3° (20) in the X-ray diffraction (XRD) profile. However, the Ag peak was barely observed when Ca salt was used alone as the anti-sintering agent. Thus, using Ca salt alone was more effective for preparation of dispersible Ag-HAp than PAA-Ca. The particle average size of Ag-HAp with 0.5 mol% of Ag content was found to be 325 ± 70 nm when the formation of large particle-aggregations was prevented, as determined by dynamic light scattering instrument. The antibacterial activity of the Ag-HAp nanoparticles possessing 0.5 mol% against E. coli was greater than 90.0%.

Conclusions

Dispersible and crystalline nano Ag-HAp can be obtained by using Ca salt alone as an anti-sintering agent. The nanoparticles showed antibacterial activity.