Synergistic effects of physicochemical parameters on bio-fabrication of mint silver nanoparticles: Structural evaluation and action against HCT116 colon cancer cells

Background: Physicochemical parameters such as temperature, pH, the concentration of the AgNO₃ and ratio of reactants act synergistically to influence the reaction kinetics, molecular mechanics, enzymatic catalysis and protein conformations that aid to affect the size, shape and biochemical corona of nanoparticles. The present study was performed to investigate the influence of reaction parameters on the bio-fabrication of silver nanoparticles (AgNPs) by using Mentha arvensis and to determine their potential to control the proliferation of colon cancer cells'. Methods: Plant-mediated method was used for the bio-fabrication and stabilization of AgNPs. Reaction parameters were arranged, and surface plasmon resonance (SPR) bands of AgNPs were collected by using a UV-Visible spectrophotometer. NPs were characterized structurally and optically by using SEM, AFM, EDX and DLS techniques. AgNPs and plant aqueous extract were tested against HCT116 colon cancer cells by using SRB assay, Annexin V assay and cell cycle analysis. Results: Spectrophotometric comparison of various reaction conditions manifested that 5 mM of AgNO₃, 60 °C in an acidic pH and a mixing ratio of 1:9 of plant extract and AgNO₃, respectively, are the optimized conditions for AgNP synthesis. Structural evaluation by SEM, AFM and particle size analysis confirmed that the NPs are <100 nm and are anisotropic, spherical, triangular and moderately dispersed in the colloidal mixture. SRB assay expressed biomass-stabilized AgNPs as effective cytotoxic particles against HCT116 colon cancer cells, and the IC₅₀ was measured at 1.7 µg/mL. Annexin V apoptosis assay further confirmed that the AgNPs induce apoptosis in a dose-dependent manner. Experimental evidence manifested that the AgNPs arrest cell cycle and expressed entrapment of a greater number of cells in the Sub-G1 phase, further verifying the anticancer abilities of AgNPs. Conclusion: These findings explain the synergistic effects of physicochemical parameters to optimize the phytosynthesis of biocompatible AgNPs to overcome the limitations of conventional chemotherapeutic treatments of colon cancer cells.