pH Alteration in Plant-Mediated Green Synthesis and Its Resultant Impact on Antimicrobial Properties of Silver Nanoparticles (AgNPs)

Abstract

Plant-mediated green synthesis is a cost-effective and eco-friendly process used to synthesize metallic nanoparticles. Experimental pH is of interest due to its ability to influence nanoparticle size and shape; however, little has been explored in comparison to the influence of this parameter on the therapeutic potential of resultant metallic nanoparticles. Our work investigated the influence of pH alternation on antimicrobial properties of plant-mediated green synthesized (using Spinacia oleracea leaf extract) silver nanoparticles. We further investigated if the antimicrobial activity was sustained at 8 weeks (after initial green synthesis). Antimicrobial properties were evaluated against Escherichia coli, Staphylococcus aureus, and Candida albicans. Our work confirmed that experimental pH in plant-mediated green synthesis of silver nanoparticles influenced their resultant antimicrobial properties. Silver nanoparticles generated at experimental pH 4,5, and nine showed activity against E. coli which was sustained at various levels over 8 weeks. No antimicrobial activity was observed against S. aureus, and weak antimicrobial activity against C. albicans. These interesting findings highlight the importance of experimental pH. Further understanding of the role experimental pH plays on resultant metallic nanoparticle properties as it relates to biological and therapeutic impact is required, which will have an impact on wider applications beyond antimicrobial activity.

Laboratory-synthesized biogenic silver nanoparticles (AgNPs) with potential therapeutic applications

“…The minimum inhibitory concentration (MIC) of the AgNPs against all tested pathogenic microbes was equivalent to 31.25 μg/100μl. These findings contrast with those of Miranda and his co-workers [20], who discovered that their synthesised AgNPs were effective against E. coli but had no antibacterial activity against S. aureus and only weak antimicrobial activity against Candida albicans. According to Khane and his colleagues [27], they found that AgNPs have antimicrobial activity against E. coli ATCC 25922, S. aureus ATCC 25923, and C. albicans.…”

“…Resazurin, a rapid screening assay, was used to test the antibacterial activities of the synthesized AgNPs against the following microbes: Escherichia coli (E. coli) (ATCC: 8739), Klebsiella pneumonia (K. pneumonia) (ATCC: 13883), Pseudomonas aeruginosa (P. aeruginosa) (ATCC: 15442), Vibreo parahemolyticu (V. parahemolyticus), Enterococcus faecalis (E. faecalis) (ATCC: 29212), Staphylococcus aureus (S. aureus) (ATCC: 25923), Bacillus subtilis (B. subtilis) (ATCC: 6633), and Candida albicans (C. albicans) (ATCC: 10231) was determined according to methodology of Miranda and his colleagues [20] with some modifications. Five µL of microbial suspension whose turbidity was adjusted to a 0.5 McFarland standard were placed in 96 wells.…”

Applications of Green Synthesized Metal Nanoparticles — a Review

“…The truncated triangular shape of the silver nanoparticle has strong antibacterial effects against E. coli. Truncated triangular silver nanoplates have a high contact area and surface reaction [185,186]. Green synthesis of silver nanoparticle structure and dimension also plays a most important role in catalyzing various types of dyes and photocatalytic degradation [134] and in the wastewater treatment process [187].…”

The Antifungal Activities of Silver Nano-Aggregates Biosynthesized from the Aqueous Extract and the Alkaline Aqueous Fraction of Rhazya stricta against Some Fusarium Species

“…Prior research found that pH might affect the characteristics of the synthesized NPs. It was found that an acidic pH of 4.5 increased the NPs antibacterial action against E. coli but had less activity against S. aureus and C. albicans [ 19 , 20 ]. This emphasizes the significance of pH and its function in the display of the NP’s biological and medicinal effects.…”

“…The addition of R. stricta root extract caused the color of the AgNPs to shift from pale yellow to orange-brown. The results indicated that these AgNPs made using R. stricta root extract and xylitol exhibited potential antibacterial action since they were monodispersed, stable, and had minimal aggregation [ 20 ]. These studies showed that biologically produced NPs outperform chemically or physically created NPs.…”