Characterization of biogenically synthesized silver nanoparticles for therapeutic applications and enzyme nanocomplex generation.

The present study describes green synthesis of silver nanoparticles (AgNPs) and inulin hydrolyzing enzyme nanocomplexes (ENC) using Azadirachta indica (Ai) and Punica granatum (Pg) leaf extracts. Surface topology and physico-chemical characteristics of AgNPs were studied using surface plasmon resonance (SPR), FTIR, SEM, AFM and EDX analyses. Particle size analysis using dynamic light scattering and AFM studies revealed that Ai-AgNPs (76.4 nm) were spherical in shape having central bigger nano-regime with smaller surroundings while Pg-AgNPs (72.1 nm) and ENCs (Inulinase-Pg-AgNPs ~ 145 nm) were spherical particles having smooth surfaces. Pg-AgNPs exhibited significant photocatalysis of a thiazine dye, methylene blue. Both Ai- and Pg-AgNPs showed selective antibacterial action by inhibiting pathogenic Bacillus cereus, while the probiotic Lactobacillus strains remained unaffected. Ai-AgNPs showed potential anti-biofilm effect (30% viability) on B. cereus biofilms. Pg-AgNPs showed anti-cancer effect against human colon cancer cell lines (Caco-2) resulting in 40% cell death in 48 h. Enzymes (inulinase, L-asparaginase and glucose oxidase) were successfully immobilized onto nanoparticles together with the biogenic synthesis of AgNPs and recyclability of the Inulinase-Pg-AgNPs complex was demonstrated. The study elaborates characteristics of green synthesized nanoparticles and their potential applications as anti-cancer, antibacterial and antioxidant nano drugs that could be used in food and nutraceutical industries. Enzyme immobilization on AgNPs without any toxic cross-linker opens up newer possibilites in enzyme-nanocomplex research.