Functionalized Concave Cube Gold Nanoparticles as Potent Antimicrobial Agents against Pathogenic Bacteria

Abstract

Gold (Au) is an inert metal in a bulk state; however, it can be used for the preparation of Au nanoparticles (i.e., AuNPs) for multidimensional applications in the field of nanomedicine and nanobiotechnology. Herein, monodisperse concave cube AuNPs (CCAuNPs) were synthesized and functionalized with a natural antioxidant lipoic acid (LA) and a tripeptide glutathione (GSH) because different crystal facets of AuNPs provide binding sites for distinct ligands. There was an ∼10 nm bathochromic shift of the UV–vis spectrum when CCAuNPs were functionalized with LA, and the size of the as-synthesized monodisperse CCAu nanoparticles was 76 nm. The LA-functionalized CCAu nanoparticles (i.e., CCAuLA) showed the highest antibacterial activity against Bacillus subtilis. Both fluorescence images and scanning electron microscopy images confirm the damage of the bacterial cell wall as the mode of antibacterial activity of CCAuNPs. CCAuNPs also cause the oxidation of bacterial cell membrane fatty acids to produce reactive oxygen species, which pave the way for the death of bacteria. Both CCAu nanoparticles and their functionalized derivatives showed excellent hemocompatibility (i.e., percentage of hemolysis is <5% at 80 μg of AuNPs) to human red blood cells and very high biocompatibility to HeLa, L929, and Chinese hamster ovary-green fluorescent protein (CHO-GFP) cells. Taken together, LA and GSH enhance the antibacterial activity and biocompatibility, respectively, of CCAu nanoparticles that interact with the bacteria through Coulomb as well as hydrophobic interactions before demonstrating antibacterial propensity.

Diospyros malabarica Fruit Extract Derived Silver Nanoparticles: A Biocompatible Antibacterial Agent

“…The negative surface potential brings about stronger electrostatic repulsion with the negatively charged RBCs. In both cases, the percentage (%) of hemolysis was less than that of the therapeutically acceptable hemolytic value (i.e., 5%) (Nayak et al, 2016;Hossain et al, 2019;Sarker et al, 2022). Furthermore, the variation in hemolysis percentage is due to the differences in membrane composition of human and rat RBCs (da SilveiraCavalcante et al, 2015).…”

“…The compatibility of human and rat erythrocytes with bAgNPs (i.e., Aq@AgNPs and Et@AgNPs) was investigated according to our previously established protocol (Ranjan Sarker et al, 2019;Sarker et al, 2022). Briefly, human and rat red blood cells (RBCs) were isolated from serum through centrifugation at 500 g for 10 min.…”

Green synthesis of silver nanoparticles using Phyllanthus emblica extract: investigation of antibacterial activity and biocompatibility in vivo

“…The compatibility of bAgNPs with human red blood cells (RBCs) was investigated according to our previously published protocol with minor modifications. 5,6,12 In brief, 6 mL of human blood was drawn from the donor's left hand following the venipuncture technique and collected in a tube containing 10% EDTA. The blood was then centrifuged at 500g for 10 minutes at room temperature to separate RBCs from serum.…”

“…The aim is to engineer materials at both the atomic and molecular levels to create nanostructures with superior functionalities. 4 Inorganic nanoparticles, such as gold (Au) [5][6][7][8][9] and silver (Ag), 4,7,[10][11][12][13] have been widely studied as antibacterial agents due to their excellent physical and chemical properties. Among these, silver nanoparticles (AgNPs) have been extensively utilized as antimicrobial agents in various medical applications, including wound dressings, cardiovascular and orthopedic implants, catheters, and dental composites.…”