| Summary: | Although silver nanoparticles are known for their antibacterial activity, little research has been carried out on
what synthesis method provides the most effective particles. In this study, silver nanoparticles were synthesised
via chemical reduction by using silver nitrate as the silver precursor, ascorbic acid as the reducing agent and
sodium citrate as the stabilising agent. The solutions were adjusted to several pH values employing sodium
hydroxide, citric acid or nitric acid. Dynamic light scattering and absorption spectra in the ultraviolet/visible
region characterisation revealed that employing nitric acid to adjust the pH produced more varied and larger
silver particle sizes. Then, silver nanoparticles were supported on montmorillonite and saponite through wet
impregnation or ion exchange methods. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and
transmission electron microscopy characterisation confirmed that silver nanoparticles were successfully loaded
onto the clay minerals. Next, the antibacterial activity of the samples was evaluated against Escherichia coli and
Staphylococcus aureus by determining their minimum inhibitory concentrations and minimum bactericidal concentrations. The free silver nanoparticles did not show any antibacterial activity at 125 mg/L. In contrast, the
silver-loaded samples obtained by wet impregnation and with a higher silver content displayed the strongest
antibacterial effect. Finally, the cytotoxicity of the samples was determined in GM07492-A cell line by using an
XTT colorimetric assay. The calculated IC50 values revealed that the supported silver nanoparticles were barely
toxic. Thus, the silver-loaded clay minerals obtained here are promising antibacterial materials with a high-grade
safety profile.
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