Synthesis of Silver Nanoparticles by Sodium Borohydride Reduction Method: Optimization of Conditions for High Anti-staphylococcal Activity

Aim: The aim of this research was to optimize the reaction conditions for the production of silver nanoparticles sufficiently bioactive for incorporation into pharmaceutical gels.

Methods: Silver nanoparticles were prepared by silver nitrate-sodium borohydride reduction method under different stoichiometric conditions and differences in their spectral properties were investigated while bioactivities were studied against different bacterial species. The most bioactive sample was characterized using transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy, and the influences of varying reaction conditions (pH, solvent type and solvent temperature) were investigated using the stoichiometric ratio with best bioactivity.

Results: The 25: 25 batch (sodium borohydride and silver nitrate in equal volume ratio) demonstrated the highest bioactivity which was significantly different (P = 0.05) from others. Physicochemical characterization revealed a hydrodynamic size of 17.46 d.nm (pdi 0.62) and a peak resonance mode at 450 nm. Bioactivity was highest at neutral pH conditions of reaction and improved with precursor solvent temperature, up to 45°C. Whereas the control sample of ciprofloxacin demonstrated no activity against Staphylococcus aureus, silver nanoparticles in methanol exhibited very good activity against Staphylococcus aureus.

Conclusion: It is hereby concluded that reaction conditions can affect the antimicrobial activity of silver nanoparticles, possibly by influencing the size and yield of silver nanoparticles using the silver nitrate-sodium borohydride reduction method.