Biosynthesis of Silver Nanoparticles Using Callus Extract of Catharanthus roseus var. alba and Assessment of Its Antimicrobial Activity

Objective: To express a cost efficacious and environment friendly method for the green synthesis of silver nanoparticles (AgNPs) from Catharanthus roseus var. alba (C. roseus var. alba) callus extract.
Methodology: The aqueous solution of sliver nitrate containing Ag+ ions (1 mM) are integrating 100 μL of aqueous extract of callus of C. roseus var. alba and 10 mL of 1% w/v aqueous solution of polyethylene glycol 4000 to 90 mL. This was then alkalized with 0.1 NaOH (20 μL) and treated in a microwave oven (800 W) for 40 sec for the reduction of metal ion and the reaction takes place at room temperature (250C). The reduction of the Ag+ ions by aqueous callus extract of C. roseus var. alba in the solutions was monitored by UV–Visible spectrum and further characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and x-ray diffraction (XRD). Antibacterial activity was assessed on bacterial strain of Staphylococcus aureus and Pseudomonas aeruginosa (S. aureus and P. aeruginosa) by using the disc-diffusion assay method.
Results: Characterization of AgNPs was done DLS, TEM and XRD methods. The Dynamic Light Scattering (DLS) showed the particle size distribution of the AgNPs synthesized from C. roseus var. alba callus extract was found 86.95 nm with polydispersity index (PDI) value of = 0.304. TEM images showed the formation of AgNPs with an average size of 10 nm to 20 nm. And the XRD analysis showed that the AgNPs were crystalline in nature with face-centered-cubic (FCC). For the assessment of antibacterial activity the concentration of AgNPs 25 μL, 50 μL, 100 μL and 150 μL were used against both the bacterial strain S. aureus and P. aeruginosa, the zone of inhibition found 4 mm, 7 mm, 16 mm and 23 mm as well as 5 mm, 9 mm, 19 mm and 26 mm respectively.
Conclusions: Aseptically engendered callus of C. roseus var. alba demonstrates vigorous potential for synthesis of silver nanoparticles by rapid reduction of Ag+ to Ag. The biologically synthesized AgNPs showed more preponderant antibacterial effect against S. aureus and P. aeruginosa.