GREEN-SYNTHESIZED AZADIRACHTA INDICA–MEDIATED AGNPS WITH PHYSICOCHEMICAL CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY AGAINST DENTAL PSEUDOMONAS AERUGINOSA

Abstract

The growing prevalence of antimicrobial resistance (AMR) in opportunistic bacteria, especially Pseudomonas aeruginosa, poses a serious challenge in both dental and broader clinical environments. Objectives: In response to this issue, green nanotechnology—particularly plant-mediated silver nanoparticles (AgNPs)—has gained attention as an eco-friendly and biocompatible antimicrobial strategy. This study aimed to synthesize silver nanoparticles using Azadirachta indica (neem) leaf extract and to assess their antibacterial efficacy against dental isolates of P. aeruginosa. Methodology: Silver nanoparticles were fabricated through a modified reduction approach in which A. indica leaf extract served simultaneously as a reducing and capping agent. The synthesized nanoparticles were extensively characterized using UV–visible spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic light scattering (DLS) to determine their structural, morphological, and physicochemical properties. Antibacterial activity was evaluated by agar well diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays at concentrations of 10, 20, and 30 μg/mL. A 0.2% chlorhexidine solution was employed as a positive control. Results: XRD patterns confirmed the crystalline structure of the AgNPs, with an estimated average crystallite size of 16.07 nm. FTIR analysis identified bio functional groups from neem extract involved in nanoparticle stabilization, while SEM imaging revealed predominantly hexagonal-shaped particles. UV–visible spectroscopy showed a distinct surface plasmon resonance peak at 238 nm, and DLS analysis indicated a hydrodynamic diameter of 144.22 nm. The neem-mediated AgNPs exhibited dose-dependent antibacterial activity against P. aeruginosa, with mean inhibition zones of 12 ± 1.13 mm, 14 ± 2.05 mm, and 17 ± 1.15 mm at 10, 20, and 30 μg/mL, respectively. Notably, the antibacterial effect at 30 μg/mL was comparable to that of chlorhexidine (18 ± 1.46 mm). Conclusion: This study demonstrates that A. indica–derived silver nanoparticles possess significant antibacterial potential against P. aeruginosa. Their strong activity, coupled with a green and sustainable synthesis approach, suggests that these nanoparticles could serve as a promising alternative to conventional antimicrobials however, further in vivo studies and comprehensive toxicity evaluations are necessary before clinical or dental applications can be considered.