Synthesis and antibacterial study of silver nanoparticle-Bac8c conjugates

Abstract Background . Antimicrobial resistance is listed as one of the top ten global health issues driven by the misuse and overuse of antibiotics. Silver nanoparticles (AgNPs) have been used extensively in the past few decades as an antimicrobial agent to treat various skin infections due to their broad antibacterial spectrum. Despite their efficacy, high toxicity remains a major drawback. AgNPs can be conjugated with antimicrobial peptides (Bac8c), to form AgNP-Bac8c conjugates with enhanced antibacterial effect. Method . AgNPs were synthesised via the chemical reduction method. Various concentrations of Bac8c were used to mix with AgNPs to form AgNP-Bac8c conjugates. UV–vis spectra, size, and zeta potential measurements were performed on AgNPs and conjugates. FESEM/EDX was used to study morphology and actual size of AgNPs and the optimised conjugate (AgNP-Bac8c-8). Broth microdilution assay and MTT assay were performed to evaluate the antibacterial effects and cytotoxicities of AgNPs, Bac8c, and AgNP-Bac8c-8. Results . Synthesised AgNPs showed a λ max at 418 nm in UV–vis spectrum, possessed an actual size of 37.8 ± 9.8 nm, and a zeta potential of −27.8 mV. AgNP-Bac8c-8 was found to be the optimised conjugate. AgNP-Bac8c-8 showed a size 51 ± 8.4 nm under FESEM and a zeta potential of +5 mV. AgNP-Bac8c-8 has demonstrated an enhanced antibacterial effect against both sensitive and resistant bacteria ( Staphylococcus aureus and Pseudomonas aeruginosa ) in contrast to AgNPs and Bac8c alone. AgNP-Bac8c-8 showed a lower cytotoxicity towards human skin cells as compared to Bac8c, but not AgNPs alone. Conclusion. AgNP-Bac8c conjugate has demonstrated an enhanced antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa , including resistant strains. A lower cytotoxicity was reported for AgNP-Bac8c compared to Bac8c, but not statistically significant, in terms of toxicity, compared to AgNPs. Stability, bioactivity, and cytotoxicity of the conjugate can be optimised further in future studies to provide a potent treatment option for skin infections.