Materials that contain silver nanoparticles possess strong antimicrobial properties allowing to decrease the risk of developing a wound infection. Hydroxyapatite is naturally occurring mineral based on calcium phosphate This material has a high degree of biocompatibility, exhibits osteoconductive behavior and can promote chemical bonding between implanted material and living tissue.
The main objective of this study was estimation of the inhibition of bacterial growth on the surface of hydroxyapatite doped with variable amounts of silver nanoparticles, synthesized in situ, against bacteria such as E.coli, S. aureus and E. faecalis respectively.
This evaluation was analyzed by means of Kirby-Bauer method and was based on measurement of sensitivity of bacteria exposed to hydroxyapatite sample doped by silver nanoparticles by culturing bacteria on solid growth media surrounding sources of tested substances. Mueller Hinton agar was used as a culture medium. The density of bacterial suspensions was adjusted to 0,5 McFarland unit. 9 mm discs containing suspensions of bone substitute (100 mg/ml) were placed on agar plate. The samples were incubated for 24 h at 37˚C. Prior to analysis hydroxyapatite was obtained by calcination of bone pulp. The first sample contained pure hydroxyapatite, second hydroxyapatite modified with 1000 ppm of silver nanoparticles and third HAp with 500 ppm of AgNPs.
Table 1. Evaluation of inhibition of bacterial growth
Table 1 presents the results of measured zones of inhibition. Due to the presence of silver nanoparticles, samples 2 and 3 exhibited antibacterial activity on E. coli and S. aureus. Notably, the size of inhibition zone is determined by the concentration of silver nanoparticles. A higher content of AgNPs lead to formation of larger zone of inhibition. Interestingly, the E. faecalis bacteria are not sensitive to any sample.
Samples 2 and 3 showed an increased antimicrobial activity against S. Aureus leading to a decrease in viability of the bacterial strain. A sample of pure hydroxyapatite does not exhibit a strong antibacterial effect.
The results showed that the antibacterial activity of tested materials, except the pure hydroxyapatite, reached the highest values against E.coli and S. aureus. Kirby-Bauer tests revealed that the samples 2 and 3 show inhibitory activity and in the future can be used as a bone substitutes with valuable antimicrobial properties.
This work was financed by the National Centre for Research and Development under the Lider project contract no. 037/481/L-5/13/NCBR/2014
References:
[1] Ciobanu C.S., Iconaru L.S., Le Coustumer P., Nanoscale Res Lett. 2012; 7(1): 324.