The impact of varying sizes of silver nanoparticles on the induction of cellular damage in Klebsiella pneumoniae involving diverse mechanisms

Silver nanoparticles (AgNPs) are extensively studied as potent antibacterial agents targeting antibiotic-resistant pathogens. Cellular damage induced through various mechanisms that can affect multiple cell components like the outer membrane, enzymes, and proteins is closely linked to their chemical and morphological characteristics. We investigated the impact of AgNPs’ size on their antibacterial effectiveness using two differently sized nanoparticles: silver nanoparticle- (AgCL) with an average size of 21 nm and silver nanoparticle- (AgCS) with an average size of 13 nm, derived from and through environmentally friendly methods. The study evaluated their antibacterial effects by assessing morphology changes via scanning electron microscopy, metabolic alterations using Fourier transform infrared (FT-IR) spectroscopy, and oxidative stress responses through biochemical markers in cells exposed to AgNPs. The results showed that both AgCL and AgCS exhibited remarkable antibacterial activity, evidenced by inhibition zones of 14 ± 1.5 and 16 ± 1.0 mm, respectively. Morphological changes in cells treated with AgNPs were size dependent, with notable alterations noted. FT-IR spectroscopy revealed size and concentration-dependent biochemical changes, particularly in shifts in functional groups involved in the fluidity of cell wall lipid, and protein structure. Exposure to AgNPs led to increased oxidative stress markers like lipid peroxides and reduced levels of enzymatic and non-enzymatic antioxidants, more prominently observed with smaller AgCS nanoparticles (13 nm). AgNPs induce oxidative stress and morphological changes in strains, with smaller nanoparticles demonstrating greater efficacy. These findings underscore the importance of nanoparticle size in optimizing the antibacterial properties against pathogens.