eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2022-12-20 19 4 1065 1078 10.13005/bbra/3056 42310 article Rajni Mishra 1 Ketki Gwalani Nandiata Nashikkar 1 Sunita Bundale 1 Hislop School of Biotechnology Hislop College Nagpur-440001 Maharashtra India Azadirachta  indica  (Neem ) is an important  medicinal plant  with proven strong antiseptic, antiviral, antifungal and antibacterial properties. The study here presents the antibacterial and QS (Quorum Sensing) inhibitory potential of biogenic Silver nanopaticles (AgNPs) from   Azadirachta  indica  leaf extracts. The nanoparticles were synthesized using an aqueous extract of Azadirachta  indica  leaves and  silver nitrate solution. The size, crystal structure, elemental composition and other physical properties of nanoparticles were determined using different microscopic and spectroscopic techniques. The average diameter of the nanoparticles  was  found to  be between 20-43 nm with  crystalline morphology. These extracellularly  synthesized  AgNPs strongly inhibited Gram negative pathogenic species and  exhibited   demonstrable anti- Quorum Sensing (QS) activity as evident from pigment inhibition and 75- 80% decrease in  biofilm mass on AgNPs treatment in a dose dependent manner. https://www.biotech-asia.org/vol19no4/antibacterial-and-anti-quorum-sensing-studies-of-extracellularly-synthesized-silver-nanoparticles-from-azadirachta-indica-neem-leaf/ Azadirachta  indica; AgNPs; Anti –Quorum Sensing; biofilm; biomedical application; nanotechnology;  nanoparticle  concentration;  Anti –Quorum Sensing