Shape dependent physical mutilation and lethal effects of silver nanoparticles on bacteria

Abstract

In this report, spherical silver nanoparticle (AgNP-sp) and rod-shaped silver nanoparticle (AgNR) were prepared by chemical reduction method and their antibacterial activity against various Gram-positive and Gram-negative bacteria had been evaluated for their efficiency. Minimal inhibitory concentration (MIC) tests were conducted to study the antibacterial properties, and substantiated with killing kinetics of silver nanoparticles (AgNPs). The study revealed that both AgNP-sp and AgNRs are good antibacterial candidates. Bacterial sensitivity to nanoparticles (NPs) was found to vary depending on microbial species. Disc diffusion studies revealed the greater effectiveness of AgNP-sp and AgNR against Klebsiella pneumoniae AWD5 at the doses of 249 and 392 µg. The dose dependent activities of prepared NPs were also observed on the batch studies of disc diffusion and MIC with various strains. The optical and morphological structures of NPs were analyzed by UV-visible, XRD, FE-SEM and TEM. Further, FESEM of bacterial culture treated with AgNPs confirmed antibacterial activity of NPs by showing rupture of bacterial cell wall. Also, the genome of test organism was found to have CusCFBA and CusRS operons. The killing kinetics confirmed that the death rate of K. pneumoniae was higher against AgNP-sp as compared to AgNR.

Silver Nanoparticles Derived from Albizia lebbeck Bark Extract Demonstrate Killing of Multidrug‐Resistant Bacteria by Damaging Cellular Architecture with Antioxidant Activity

“…It has been reported that the antibacterial or bactericidal properties of silver nanoparticles are shape and size‐dependent and smaller particles (<30 nm) were more effective against K. pneumoniae and S. aureus , while spherical particles are more active than rod shape . In our study, the nanoparticles Ag‐NP‐AE is spherical with an average diameter of 27 nm, that may attribute to the release of silver ions responsible for bactericidal activity of Ag‐NP‐AE at extremely low concentrations (0.5–0.84 μM or 0.085–0.143 μg); while AE of A. lebbeck bark showed anti‐bacterial activity at 128–1024 μg/mL, i. e., at much higher concentrations against all the bacterial isolates tested.…”

“…To cater the need scientists are looking into a metal nano‐particle based drugs, as nano‐sized molecules (<100 nm) have larger surface area than their volume, and thus able to penetrate the microbial cells faster to kill at nano‐dose . Another advantage is its ability to kill bacteria on contact, by bypassing the bacterial resistant mechanisms i. e., enzymatic inactivation, decreased cell permeability, altered target site, increased efflux due to overexpression of efflux pumps, and mutation of existing genes or acquiring new genes . In this study, we have reported the biosynthesis of silver nanoparticles using AgNO 3 and aqueous extract of bark of a traditionally used well known ethnomedicinal plant as reducing and stabilizing agents, because metallic nanoparticles from medicinal plant extracts posse's biocompatibility and antimicrobial activity.…”

“…The global spread of multidrug‐resistant bacteria and biofilm‐associated infections, along with the emerging and re‐emerging pathogens necessitate new antimicrobials. To cater the need scientists are looking into a metal nano‐particle based drugs, as nano‐sized molecules (<100 nm) have larger surface area than their volume, and thus able to penetrate the microbial cells faster to kill at nano‐dose . Another advantage is its ability to kill bacteria on contact, by bypassing the bacterial resistant mechanisms i. e., enzymatic inactivation, decreased cell permeability, altered target site, increased efflux due to overexpression of efflux pumps, and mutation of existing genes or acquiring new genes .…”

“…Several studies reported the broad‐spectrum antimicrobial activity of silver nanoparticles, including the drug‐resistant S. aureus , K. pneumonia , E. coli , E. faecalis , P. aeruginosa , A. baumannii , and M. tuberculosis . The silver nanoparticles synthesized with AgNO 3 and leaf extract of Annona reticulata showed potent activity against Bacillus cereus and Staphylococcus aureus at 125 and 31.25 μg/mL; while it inhibits Escherichia coli , Pseudomonas aeruginosa and Candida albicans at 62.5 μg/mL .…”

Review of the effects of silver nanoparticle exposure on gut bacteria

“…AgNPs are generally obtained from colloidal dispersions, and depending on the method used during synthesis could display a variety of morphologies, including nanocubes, nanoprisms, nanospheres, triangular nanoplates and rod‐like shapes (Huang, Zhai, Dong, & Wang, ; Sarkar, Kapoor, & Mukherjee, ). A study comparing the antibacterial activity of spherical and triangular Ag nanoprisms against Escherichia coli showed that they exerted greater bacterial toxicity due to their sharp edges with triangular shape (Acharya et al, ). Similarly, truncated triangular AgNPs display stronger biocidal action than that observed by spherical and rod‐shaped NPs (Pal, Tak, & Song, ).…”