Comparative evaluation of antibacterial efficacy of silver nanoparticles synthesized with Cannabis sativa extract at different concentrations

Abstract

In recent years, concern about the rise of super-resistant bacteria and the environmental pollution associated with the inappropriate use of antibiotics and the waste generated during their production has grown significantly. In response to this problem, innovative solutions have been proposed, such as the use of silver nanoparticles (AgNP), recognized for their potent antimicrobial properties against a wide range of organisms, including pathogenic bacteria. This study presents an innovative and environmentally friendly approach to the synthesis of silver nanoparticles using sonotrode, where Cannabis sativa extract acts as a reducing agent, replacing sodium borohydride (NaBH₄), a commonly used but highly polluting and carcinogenic chemical reagent. The research explored the use of different concentrations of C. sativa in the green synthesis of AgNP, evaluating their physicochemical properties and antimicrobial efficacy. To confirm the concentration, chemical composition and structural features of the nanoparticles, techniques such as atomic absorption spectroscopy (AAS), dispersion X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were employed. Scanning electron microscopy (SEM) analysis revealed details about the morphology and average size of the silver nanoparticles. Finally, the antibacterial efficacy of the nanoparticles was evaluated by the agar dilution method, underlining the potential of this innovative approach in the fight against resistant bacteria and environmental pollution. The results obtained show that the 0.5% Bio-AgNPs samples produced 53% nanoparticles, while the 2% Bio-AgNPs produced 87%. EDX analysis confirmed the presence of silver (Ag), while FTIR spectra indicated the presence of phenols, flavonoids, amino groups, alkanes, and alkenes. Ag–Ag metal bond vibrations were observed in Raman spectroscopy, and SEM analysis revealed the formation of predominantly spherical nanoparticles with sizes less than 50 nm. Furthermore, bacteriological assays demonstrated that 50, 25, and 12.5 ppm concentrations of C-AgNPs and Bio-AgNPs showed significant inhibition, highlighting that 2% C. sativa provided the best antimicrobial property. The observed biocompatibility, successful reduction of silver nitrate, and remarkable antibacterial efficacy of the synthesized nanoparticles underline the great potential of green synthesis strategies in nanoparticle production. These findings suggest that nanoparticles synthesized using this method are not only effective, but also compatible with an environmentally sustainable approach.