Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

Abstract

AbstractAg-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10-xAgx(PO4)6(OH)2,xAg = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants ofa = b = 9.435 Å,c = 6.876 Å forxAg = 0.05,a = b = 9.443 Å,c = 6.875 Å forxAg = 0.2, anda = b = 9.445 Å,c = 6.877 Å forxAg = 0.3 are in good agreement with the standard ofa = b = 9.418 Å,c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity againstStaphylococcus aureus,Klebsiella pneumoniae,Providencia stuartii,Citrobacter freundiiandSerratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest againstS. aureus,K. pneumoniae, P. stuartii, andC. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity onP. stuartiiandC. freundii. The absorbance values measured at 490 nm of theP. stuartiiandC. freundiiin the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (xAg = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase ofxAgin the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii).