Antimicrobial Properties of Silver-Infused Bioactive Glass

Objectives: Previous research has shown that the incorporation of releasable silver ions into bioactive glass (BAG) produces bactericidal outcomes against common bacteria. However, the effect of the silver-containing BAG against streptococcus mutans has not previously been determined. This study compared the antimicrobial activity of conventional BAG and silver-containing BAG prepared in our laboratory.
Methods: Sol-gel synthesis methods were used to formulate the BAGs. Compositions prepared are shown in Table 1. Silver nitrate and alkoxide precursors were used to synthesize the sol-gels in an argon atmosphere. Aged and heat-treated glasses were micronized to produce fine powders.

Bioactivity was assessed using FT-IR after soaking BAGs for 7 days in simulated body fluid (SBF). BAG powder (0.1g/10mL) was added into S. mutans cultures (BHI broth) in log phase, and co-incubated for 4hr, 24hr, and 48hr. Control samples received no BAG. The viability of the bacteria was determined by serial diluting and counting the colony-forming units (CFUs) on blood agar plates after 72 hour incubation (37°C, 5%CO2). ANOVA was used to look for significant differences in the data (α=0.05)
Results: FT-IR revealed that all of the glasses we tested were bioactive. Silver-containing BAGs had significantly lower CFUs compared to the control and the Ag-free BAGs. The silver-containing BAGs provided complete kill of all bacteria in the samples, resulting in zero CFU counts at 4hr, 24hr, and 48hr. BAG85 and BAG65 both provided significantly lower CFUs than the control culture.
Conclusions: Expanding the native antimicrobial effects of our sol-gel bioactive glasses through the addition of silver has provided a promising avenue to further its effectiveness and use in the field of restorative dentistry. The silver-infused glass showed superior antimicrobial effects compared to the non-silver-containing glass, and holds the potential for making composites with potent antibacterial activity.