Butea monosperma seed extract mediated biosynthesis of ZnO NPs and their antibacterial, antibiofilm and anti-quorum sensing potentialities

Nanoparticles (NPs) prepared through safer, eco-friendly and natural-based products can be used various applications including antimicrobial and biomedical applications. Quorum sensing (QS) is a complex system for intercellular communication that regulates the expression of many virulence determinants, in the opportunistic Pseudomonas aeruginosa. Thus, the disruption of QS-mediated communication system could be an alternative strategy to combat infection caused by drug resistant P. aeruginosa. In this study, zinc oxide nanoparticles (ZnO NPs) were synthesized by using seed extract of Butea monosperma and further characterized by XRD, SEM and TEM. The biosynthesized ZnO NPs were then subjected to the investigation of their antibacterial, antibiofilm activities as well as the anti-quorum sensing potentialities for biomedical applications. The minimum inhibitory concentration (MIC) value against P. aeruginosa was found 1600 µg/ml, and it was found that ZnO NPs effectively reduced virulence factors Viz. swarming and swimming of P. aeruginosa by 62.8 and 45%, respectively. Exopolysaccharides production was also affected by ZnO NPs which indicate the disruption of biofilm formation. Further, the in silico docking analysis displayed that ZnO NPs efficiently interacted within QS (Las/Rhl) mechanism of P. aeruginosa by binding to the catalytic cleft of LasI synthase (Gly-116-ZnO = 2.8 A), RhlI synthase (Gly-180-ZnO = 3.7 A) and transcription receptor protein LasR receptor (Asn-141-ZnO = 2.9 A), RhlR receptor (Tyr-72-ZnO = 2.6 A). Thus, it was concluded that the effective interaction of ZnO NPs with Las and Rhl system led to the inactivation of autoinducers such as N-acyl homoserine lactones (AHL) molecules which finally led to the inactivation of QS and down regulation of virulence determinants. Consequently, the present in vitro and in silico results obtained suggest that the synthesized ZnO NPs can be efficiently used as potent antimicrobial agents to prevent the colonization, biofilm formation as well as anti-QS-mediated determinants caused by pathogenic drug resistant bacteria.