Antibacterial nanosized silver substituted hydroxyapatite: Synthesis and characterization

Abstract

The silver (0.5-3 at %) substituted nanosize hydroxyapatites (AgHAs) were synthesized by microwave processing. The X-ray diffraction (XRD) peaks are very broad, indicating that the AgHAs were of nanosize (30 nm). Transmission electron microscopy analysis shows needle-like morphology of AgHA, having length 60-70 nm and width 15-20 nm. The AgHA phase was stable up to 700 degrees C without any secondary phases. The antibacterial effect of AgHA against Escherichia coli and Staphylococcus aureus was observed by spread plate method, even for low concentration of silver ions (0.5%) with 1 x 10(5) cells/mL of respective bacterial culture, after a 48 h incubation period. However, some colonies of E. coli were seen with a high dose of 1 x 10(8) cells/mL after 24 h. The zone of inhibition by disc diffusion test method was found to vary with the amount of silver in the sintered AgHA pellets, for both the bacteria, after 24 h of inoculation. Osteoblast cell attachment in varying density was noticed on AgHA samples with 0.5, 1.0, and 1.5% silver substitution. However, osteoblast spreading was significantly greater on 0.5% AgHA compared to 1.0 or 1.5% substituted AgHA samples. Thus, the low amount of AgHA has a potential of minimizing the risk of bacterial contamination, without compromising the bioactivity, and is expected to display greater biological efficacy in terms of osseointegration.

Antimicrobial activity of hemocompatible silver doped hydroxyapatite nanoparticles synthesized by modified sol–gel technique

“…(0.128 nm) is larger than Ca 2? (0.099 nm) it resulted in increase in lattice parameters (Rameshbabu and Prasad Rao 2007;Stanic et al 2011). Figure 2, shows the FTIR spectra of HAp and Ag-HAp samples.…”

“…Antimicrobial activity for Ag nanoparticles is reported in the range 1.69-100 lg/ml for various bacterial cultures (MarambioJones and Hoek 2010; Kvitek et al 2008;Kim et al 2011;Sondi and Sondi 2004). Silver based HAp nanocomposites have been shown to exhibit antimicrobial activity in growth medium where the Ag concentration ranges from 10 to 70 lg/ml for Gram-negative and Gram-positive cultures (Diaz et al 2009;Rameshbabu and Prasad Rao 2007). In this study, Ag-HAp exhibited antimicrobial activity at a much lower silver concentration of 7 lg/ml against E. coli and at 15 lg/ml for S. aureus.…”

“…The success of these orthopedic and dental implants is dependent on implant osteointegration, but the long term survival is dependent on its resistance to bacterial infections (Chen et al 2006). A disadvantage of HAp is that, proteins, amino acids, and other organic substances are easily adsorbed, which could create an environment conducive for the growth of bacteria on its surface leading to infection at the implant site, accompanied by decreased penetration of antibiotics and reduced blood supply (Rameshbabu and Prasad Rao 2007). When microorganisms adhere onto implant surfaces, they can form biofilms wherein microorganisms tend to be more resistant to antimicrobial agents (Stanic et al 2011).…”

“…In view of this, use of inorganic antibacterial agents has attracted interest for control of microbial infections. Doping HAp with antimicrobial metal ions has been exploited to address these issues (Rameshbabu and Prasad Rao 2007;Stanic et al 2011;Xiao et al 2010;Kim et al 2011).…”

“…(Diaz et al 2009;Rameshbabu and Prasad Rao 2007;Stanic et al 2011;Zheng et al 2009). In this study crystalline Ag-HAp nanorods have been synthesized at 100°C using a modified sol-gel method followed by dialysis (Jadalannagari et al 2011).…”