Colorimetric assay of apoptosis through in-situ biosynthesized gold nanoparticles inside living breast cancer cells

Abnormalities in apoptosis (More or less than normal rate) is a central factor to detect many human disorders such as many types of cancer and to show therapeutic potential of drugs. During apoptosis, oxidation of reduced gluthation (GSH) to its oxidized form, GSSG, results in a decreased GSH to GSSG ratio. Here, we used altered GSH/GSSG redox state and the release of Cyt c from mitochondria to cytosol as an indicator for apoptosis assay. This study reports a visual method for cell apoptosis assay through in-situ biosynthesized gold nanoparticles (AuNPs) inside livingcells, only after adding a sufficient amount of gold ion. After incubation of apoptotic and non-apoptotic cells with chloroauric acid solution, high level of GSH act as reducing agent in formation of AuNPs using thiol inside living non-apoptotic cells. While in the apoptotic cells, what's happening is based on changes in plasmonic coupling between AuNPs embedded along the oxidized gluthation and Cyt c aggregates in cytosol which causes color changes from red to purple. In this study, we successfully reported cell-based (inside a living cells) and cell free (cell lysis) methods for apoptosis assay of breast cancer cells and we achieved very good results in comparison with a standard apoptosis assay procedure. The linear range for MCF-7 cells detection from 30 to 3 x 10(5) cells/ml was obtained with a detection limit of 30 cells. In addition, the proposed approach is applicable to detect other apoptotic cells.