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

Abstract

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 (λ_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 via 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.