Synthesis, optimization and characterization of silver nanoparticles using the catkin extract of Piper longum for bactericidal effect against food-borne pathogens via conventional and mathematical approaches

Graphical abstract
Highlights • Catkin extract of Piper longum was used to optimize and biosynthesize AgNPs. • Biosynthesized AgNPs were characterized using UV, FTIR, TEM, XPS, GC-MS and XRD. • The antibacterial activity of the AgNPs was determined against 7 different food-borne pathogens.
Inspired with an increasing environmental awareness, we performed an eco-friendly amenable process for the synthesis of silver nanoparticles (AgNPs) using the catkins of Piper longum as an alternative approach with the existing methods of using plant extracts. The fabrication of nanoparticles occurred within 10 min. This was initially observed by colour change of the solution. UV–visible spectroscopic studies (UV–Vis) were performed for further confirmation. The analysis elucidated that the surface plasmon resonance (SPR) was specifically corresponding to AgNPs. Fourier transform infrared spectrophotometry (FTIR) studies indicated that polyphenols could possibly be the encapsulating agents. The size and shape of the nanoparticles was analysed using Transmission electron microscopy (TEM). The nanoparticles were predominant spheres ranging between 10 and 42 nm at two different scales. The formation of elemental silver was confirmed further by X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). GC-MS analysis was used to identify the possible encapsulates on the nanoparticles. The antibacterial effect of the biosynthesized AgNPs was tested against two gram-positive (Bacillus cereus and Staphylococcus aureus), and five gram-negative (Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella typhi) bacteria. Outcomes of the study suggest that these pathogens were susceptible to the AgNPs. This is the first ever international report on correlating the antibacterial effect of silver nanoparticles using mathematical modelling with a conventional antimicrobial assay. The results indicate that nanoparticles of silver synthesized using catkin extract of P. longum can be exploited towards the development of potential antibacterial agents.