Biocompatibility analysis of an electrically-activated silver-based antibacterial surface system for medical device applications

Comparative antibacterial activity of silver nanoparticles synthesised by biological and chemical routes with pluronic F68 as a stabilising agent

The authors report the comparative antibacterial activity of silver nanoparticles synthesised by biological (using Fusarium oxysporum) and chemical routes in the presence and absence of pluronic F68 as a stabilising agent. The production of silver nanoparticles was evidenced by UV-visible spectra, with absorbance at about 420 nm in the case of both biological and chemical synthesis. X-ray diffraction pattern confirmed the presence of face-centred cubic structure (FCC plane). The nanoparticles characterised by transmission and scanning electron microscopy showed spherical silver nanoparticles with size range of 5-40 and 10-70 nm in the case of biologically and chemically synthesised nanoparticles, respectively. Addition of pluronic F68 showed the stabilisation of silver nanoparticles. Antibacterial efficacy of silver nanoparticles demonstrated different inhibitory activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Overall, biologically synthesised silver nanoparticles showed higher activity as compared with chemically synthesised nanoparticles. Silver nanoparticles synthesised in the presence of pluronic F68 by the chemical route exhibited synergism in antibacterial activity as compared with those synthesised without pluronic F68. On the contrary, biogenic silver nanoparticles without pluronic F68 showed higher antibacterial potential.

Effects of cathode design parameters on in vitro antimicrobial efficacy of electrically-activated silver-based iontophoretic system

Post-operative infection is a major risk associated with implantable devices. Prior studies have demonstrated the effectiveness of ionic silver as an alternative to antibiotic-based infection prophylaxis and treatment. The focus of this study is on an electrically activated implant system engineered for active release of antimicrobial silver ions. The objective was to evaluate the effects of the cathode design, especially the cathode material, on the in vitro antimicrobial efficacy of the system. A modified Kirby-Bauer diffusion technique was used for the antimicrobial efficacy evaluations (24 h testing interval). In phase-1 of the study, a three-way ANOVA (n = 6, α = 0.05) was performed to determine the effects of cathode material (silver, titanium, and stainless steel), cathode surface area and electrode separation distance on the efficacy of the system against Staphylococcus aureus. The results show that within the design space tested, none of these parameters had a statistically significant effect on the antimicrobiality of the system (P > 0.15). Subsequently, one-way ANOVA (n = 6, α = 0.05) was conducted in phase-2 to validate the inference regarding the non-significance of the cathode material to the system efficacy using a broader spectrum of pathogens (methicillin-resistant S. aureus, Escherichia coli, Streptococcus agalactiae and Aspergillus flavus) responsible for osteomyelitis. The results confirmed the lack of statistical difference between efficacies of the three cathode material configurations against all pathogens tested (P > 0.58). Overall, the results demonstrate the ability to alter the cathode material and related design parameters in order to minimize the silver usage in the system without adversely affecting its antimicrobial efficacy.