Green synthesis of silver nanoparticles using the BT5 tea cultivar of Bangladesh: unveiling molecular mechanisms of anti-cancer activity in mice model

Silver nanoparticles (AgNPs) have sparked widespread interest due to their remarkable physiochemical capabilities, and they are now being used as a beneficial tool in the biomedical field. However, typical synthesis processes generate dangerous compounds that raise environmental and safety concerns. This is one of the main reasons for choosing a greener synthesis approach. The BT5 cultivar of green tea, which is high in phenolic and flavonoid compounds and has strong antioxidant activity (IC₅₀ ≈ 97.8 μg mL^-1), was used in an eco-friendly way to produce AgNPs. The green synthesis approach was confirmed by the rapid color change (light to dark brown) of AgNO₃ solution upon the addition of the BT5 extract. Several methods were performed to characterize the synthesized BT5-AgNPs, using UV-vis spectroscopy (<i>λ</i> _max = 424 nm), FTIR, DLS, zeta potential (-39.8 ± 0.45 mV), TGA, XRD (crystalline size = 11.25 nm), and FE-SEM (35 ± 8.36 nm). BT5-AgNPs showed strong antiproliferative properties inimical to Ehrlich-Lettre ascites carcinoma cells (EAC) of the Swiss albino variety of mice model, with low-concentration treatment (1 mg kg^-1) resulting in 52.15% cell growth inhibition. Fluorescence microscopy using DAPI staining revealed morphological alterations <i>via</i> heterochromatization and karyorrhexis. Gene expression analysis revealed upregulation of hallmark genes p53 and BAX and Bcl2 downregulation in the low- and high-concentration groups, indicating activation of the apoptotic pathway. Most likely due to cytotoxic effects and altered cellular responses, a higher dosage (5 mg kg^-1) resulted in slightly lower efficacy.