Introduction: Breast cancer remains one of the most prevalent malignancies globally with over two million new cases annually traditional treatments including chemotherapy and radiotherapy, while effective, often lead to harmful side effects, drug resistance, and damage to healthy tissues. Nanotechnology has recently emerged as a promising alternative in cancer therapy. Among various nanomaterials, silver nanoparticles (AgNPs) are particularly notable for their antimicrobial, anti-inflammatory, and anticancer properties. Biogenic synthesis of AgNPs using probiotic bacteria such as Lactobacillus casei offers a green, sustainable, and cost-effective method, avoiding toxic chemicals and producing nanoparticles with enhanced stability and biological activity. Previous studies demonstrated that biosynthesized AgNPs can induce apoptosis, inhibit proliferation, and suppress migration of cancer cells. This study aims to evaluate the cytotoxic effect of AgNPs biosynthesized by Lactobacillus casei (AgNPs-LC) on human breast cancer MCF-7 cells, analyzing dose- and time-dependent responses to identify effective concentrations with minimal toxicity.
Methods: In this study, silver nanoparticles were synthesized using Lactobacillus casei cultures and characterized by UV–Vis spectroscopy and transmission electron microscopy (TEM). Human breast cancer MCF-7 cells were purchase from Pasture Institute of Iran and cultured in DMEMand 10% FBS, followed by treating by AgNPs-LC at concentrations of 6.25, 12.5, 25, 50, and 100 µg/mL for 24, 48, and 72 hours. Cell viability was measured by the MTT assay, assessing mitochondrial activity by absorbance at 570 nm. All treatments were performed in triplicates.
Results: The result showed that fabricated AgNPs-LC have a spherical shape with an average size of 15 nm and a UV absorption peak at 458 nm. MTT data revealed a clear dose- and time-dependent decrease in cell viability. Viability remained relatively high at low concentrations after 24 hours but significantly decreased after 48 and 72 hours. Increasing concentrations of AgNPs-LC progressively reduced cell survival. The 12.5 µg/mL treatment group showed significant viability reduction without excessive toxicity, indicating a promising therapeutic window.
Conclusion: Based on our data, the produced AgNPs using Lactobacillus casei display strong cytotoxic effects on MCF-7 cancer cells. These findings suggest that biogenic AgNPs as promising candidates for adjunctive breast cancer therapy, potentially reducing drug resistance and side effects. Therefore, further research should investigate molecular apoptotic pathways, reactive oxygen species (ROS) production, and conduct in vivo studies.