Polyphenol stabilized colloidal gold nanoparticles from Abutilon indicum leaf extract induce apoptosis in HT-29 colon cancer cells.

Green synthesized gold nanoparticles have received substantial attention owing to their biomedical applications, particularly in cancer therapy. Although anticancer activities of green synthesized gold nanoparticles have been reported earlier, the underlying mechanism behind their anticancer activity is still to be understood. The present study, describes the green synthesis of Abutilon indicum gold nanoparticles (AIGNPs) from Abutilon indicum leaf extract (AILE) and their cytotoxic mechanism in colon cancer cells. Dimensions of spherical shaped AIGNPs were found to be in the range of 1-20nm as determined by TEM. GC-MS and FTIR analysis indicated the presence of polyphenolic groups in AILE, which might have been involved in the stabilization of AIGNPs. In vitro free radical scavenging analysis revealed the radical quenching activity of AIGNPs. Further, the AIGNPs exhibited cytotoxicity in HT-29 colon cancer cells with IC50 values of 210 and 180μg/mL after 24 and 48h. This was mediated through nuclear morphological changes and cell membrane damage as evidenced by acridine orange/ethidium bromide, propidium iodide and AnnexinV-Cy3 staining methods. Mechanism of the observed cytotoxicity of AIGNPs was explained on the basis of increased levels of reactive oxygen species and simultaneous reduction in cellular antioxidants, which might have caused mitochondrial membrane potential loss, DNA damage and G1/S phase cell cycle arrest. Expression of cleaved Caspase-9, Caspase-8, Caspase-3, Lamin A/C and PARP, provided the clues for the induction of intrinsic and extrinsic apoptosis pathways in AIGNPs treated HT-29 cells. The study provides a preliminary guidance towards the development of colon cancer therapy using green synthesized gold nanoparticles.