Silver Nanoparticles: Conventional Vs Ultrasound Synthesis, Inhibition of Staphylococcus-aureus

Objectives: Synthesize of AgNPs by ultrasound and conventional techniques, analyze morphology, particle size, Staphylococcus-aureus culture’s antibacterial effect and in vitro cytotoxicity.
Methods: AgNPs were obtained by reduction of silver-nitrate (AgNO₃) and sodium-borohydride (NaBH₄), with incorporation of sodium citrate; synthesized conventionally group was obtained in magnetically-stirring and ultrasonic-medium group. Samples were centrifuged (14000rpm/10min). AgNPs were characterized by UV-Vis-Spectroscopy and Electronic-Transmission-Microscopy. Evaluation of antibacterial effect in S-aureus cultures by disk diffusion test using an adjusted solution (0.5-McFarland), MTT assay was performed to evaluate cytotoxicity using mouse fibroblast cell-line. One-Way ANOVA was applied.
Results: AgNPs were synthesized by conventional magnetically-stirring technique showed UV-Vis absorbance in 400nm, smaller (10nm) particles with spherical morphology compared with synthesized AgNPs by ultrasonic technique (410nm of UV-Vis absorbance, spherical nanoparticles with 50nm in size). Inhibition of S-aureus in conventionally synthesized AgNPs (2.16mm, S=±0.14) significantly higher (p>0.05) when compared with ultrasound (1.08mm, S=±0.14) control-group lincomycin = 29 mm, no-cytotoxic effect was demonstrated with both synthesized AgNPs groups (p<0.05).
Conclusions: The magnetically stirring technique to obtain AgNPs is more effective in the inhibition of Staphylococcus-aureus, even though ultrasound technique provides good physical characteristics, they presented less antimicrobial activity. Both AgNPs techniques resulted to be non-cytotoxic, which emphasizes the interest for incorporation into biomaterials. Acknowledgements: Projects (DGAPA-UNAM): PAPIIT-TA200414, PAPIME-PE202214; CONACyT-México(CB176450) and Lourdes Palma (INB-UNAM) for the technical support.