Integrating QQ with Nano-techniques – A Potent Antibacterial Therapy

Biofilms are highly organized 3D structures where bacteria are embedded in a self-produced complex matrix, made of extracellular polymeric substances (EPS). Biofilms are produced via the quorum sensing (QS) pathway. QS is mediated by bacteria producing, releasing and detecting extracellular signaling molecules called autoinducers (AIs). If AIs are produced more, then the biofilm’s cell density will be greater, these biofilms are responsible for microbial activity. As of now there are at least three known mechanisms for QS pathways. Those include (1) luminescence inducer/regulator (LuxI/LuxR)-type quorum sensing with acyl-homoserine lactones (AHL) as signal molecules (in Gram-negative bacteria); (2) oligopeptide two-component-type quorum sensing with short peptides as signal molecules (in Gram-positive bacteria); and (3) AI-2 quorum sensing: expressed via the luxS gene (in both types of bacteria). To produce antimicrobial activity, the QS mechanism needs to be suppressed. Quorum quenching (QQ), works against QS, which, in turn, helps in antimicrobial activity. In some cases, AHL is modified to disrupt QS mechanisms. For example, Agrobacterium and Pseudomonas, can cleave their own AHL signals. Recent research in nanotechnology has resulted in the development of nanoparticle drugs, which showed the anti-QS mechanisms. On the basis of their unique properties, nanoparticles act as anti-infective agents, so they are used in drug development. Nanoparticles (NPs) do not destroy cell wall to kill the microbes but they act at cellular level, that is the biochemical and molecular level, and destroy the membranes. Some of the nanoparticles used in drug development are silver NPs, gold NPs, ZnO NPs, SiO2 NPs and TiO2 NPs. Nanoparticles help in eliminating the QS, which leads to a low density biofilm (through a decrease in bacterial growth) which helps to treat and prevent bacterial infection.