Highly Stable Graphene-Based Nanocomposite (GO–PEI–Ag) with Broad-Spectrum, Long-Term Antimicrobial Activity and Antibiofilm Effects

Abstract

Various silver nanoparticle (AgNP)-decorated graphene oxide (GO) nanocomposites (GO-Ag) have received increasing attention owing to their antimicrobial activity and biocompatibility; however, their aggregation in physiological solutions and the generally complex synthesis methods warrant improvement. This study aimed to synthesize a polyethyleneimine (PEI)-modified and AgNP-decorated GO nanocomposite (GO-PEI-Ag) through a facile approach through microwave irradiation without any extra reductants and surfactants; its antimicrobial activity was investigated on Gram-negative/-positive bacteria (including drug-resistant bacteria) and fungi. Compared with GO-Ag, GO-PEI-Ag acquired excellent stability in physiological solutions and electropositivity, showing substantially higher antimicrobial efficacy. Moreover, GO-PEI-Ag exhibited particularly excellent long-term effects, presenting no obvious decline in antimicrobial activity after 1 week storage in physiological saline and repeated use for three times and the lasting inhibition of bacterial growth in nutrient-rich culture medium. In contrast, GO-Ag exhibited a >60% decline in antimicrobial activity after storage. Importantly, GO-PEI-Ag effectively eliminated adhered bacteria, thereby preventing biofilm formation. The primary antimicrobial mechanisms of GO-PEI-Ag were evidenced as physical damage to the pathogen structure, causing cytoplasmic leakage. Hence, stable GO-PEI-Ag with robust, long-term antimicrobial activity holds promise in combating public-health threats posed by drug-resistant bacteria and biofilms.

Comparative Study on the Fungicidal Activity of Metallic MgO Nanoparticles and Macroscale MgO Against Soilborne Fungal Phytopathogens

“…Analogously, the destabilization of the cell outer membrane in gram-negative bacteria was observed through the accumulation of envelope protein precursors after exposure to AgNPs and GO-AgNPs, even in gram-positive bacteria with a strong physical barrier (Chen et al, 2014;Zhao et al, 2018). Previous results, reported by Leung and coworkers, proved that nMgO directly interacted with Escherichia coli and caused the downregulation of outer membrane proteins (Omp), such as channel porins and ion channel proteins, as well as disturbance of proteins involved in the membrane lipid metabolism process, making cells liable to lyse (Leung et al, 2014).…”

“…Several studies have suggested that the formation of reactive oxygen species (ROS) and its accumulation in cells seem to be the underlying mechanism of metal nanoparticles against bacterial pathogens, particularly because the generated ROS directly destroy the cell multiplication capacity (Horst et al, 2013;Chen et al, 2014). It is generally believed that microorganism disinfection relies on the direct interaction between nanoparticles and biological cells (Chen et al, 2012;Zhao et al, 2018). In particular, Huang et al, further demonstrated that peptide linkages in the bacterial cell wall are physically damaged by the generation of superoxide ions on the surface of nMgO (Huang et al, 2005).…”

Toxicological response of the model fungus Saccharomyces cerevisiae to different concentrations of commercial graphene nanoplatelets

“…In relation to studies investigating the biological impact of GFNs on microbial systems, many publications have reported the antibacterial properties of different graphene derivatives and composites [9][10][11][12][13] . In case of the interactions between fungi and graphene-based materials, most of the efforts have focused on improving the antifungal properties of GFNs through their modification with antimycotic drugs, peptides or metals [14][15][16][17] .…”

Bioactive silver phosphate/polyindole nanocomposites

“…6 and 16) to 48 h. 30 Studies of "prolonged exposure" reported either antibacterial activity aer long term storage of the nanomaterials repeated exposures 31,32 and the exposure of bacteria to such nanomaterials for durations longer than 24 h with subsequent monitoring of bacterial growth are relatively uncommon. 31,33 Our understanding of the underlying mechanism of the existing long term antibacterial activity of nanoparticles in vitro/ vivo is still relatively nascent. 34 The simultaneous existence of ROS and non ROS mediated long term antibacterial activity in nanomaterials is therefore an important area of research.…”