The increasing occurrence of antibiotic-resistant pathogens, especially superbugs, is compromising the efficacy of traditional antibiotics. Silver nanoparticles (AgNPs) loaded graphene oxide (GO) nanocomposite (GO-Ag) has drawn great interest as a promising alternative antibacterial material. However, GO-Ag nanocomposite often irreversibly aggregates in physiological solutions, severely influencing its antibacterial capacity and practical application. Herein, a PEGylated and AgNPs loaded GO nanocomposite (GO-PEG-Ag) is synthesized through a facile approach utilizing microwave irradiation, while avoiding extra reducing agents. Through PEGylation, the synthesized GO-PEG-Ag nanocomposite dispersed stably over one month in a series of media and resisted centrifugation at 10 000×g for 5 min, which would benefit effective contact between the nanocomposite and the bacteria. In contrast, GO-Ag aggregated within 1 h of dispersion in physiological solutions. In comparison with GO-Ag, GO-PEG-Ag showed stronger bactericidal capability toward not only normal Gram-negative/positive bacteria such as E. coli and S. aureus (∼100% of E. coli and ∼95.3% of S. aureus reduction by 10 μg/mL nanocomposite for 2.5 h), but also superbugs. Moreover, GO-PEG-Ag showed lower cytotoxicity toward HeLa cells. Importantly, GO-PEG-Ag presented long-term antibacterial effectiveness, remaining ∼95% antibacterial activity after one-week storage in saline solution versus <35% for GO-Ag. The antibacterial mechanisms of GO-PEG-Ag were evidenced as damage to the bacterial structure and production of reactive oxygen species, causing cytoplasm leakage and metabolism decrease. The stable GO-PEG-Ag nanocomposite with powerful and long-term antibacterial capability provides a more practical and effective strategy for fighting superbugs-including pathogen threats in biomedicine and public health.

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.

We developed a real-time colorimetric method based on LAMP-integrated microfluidic chip system for diagnosing multiple respiratory viruses.