Biocompatible GSH-Coated CDS/ZNS Quantum Dots for Fluorescent Imaging of Cancer and Epithelial Cell Lines

The present paper presents the development and characterization of glutathione-coated CdS/ZnS core-shell quantum dots (QDs) for biocompatible cellular imaging and targeting. CdS/ZnS quantum dots were produced using a one-pot high-temperature technique and made water-soluble through ligand exchange with DL-cysteine. Glutathione (GSH) was coupled by EDC/NHS chemistry to enhance stability and biocompatibility, resulting in quantum dots (QDs) with a hydrodynamic diameter of approximately 20 nm, robust blue fluorescence emission at 455 nm, and a quantum yield of 39%. FTIR validated the effective alteration of the GSH surface. MTT studies on MCF-7 and HeLa cells revealed robust cell viability (>90%) at doses up to 10 μg/mL, signifying little cytotoxicity. Confocal imaging demonstrated effective cellular absorption, whereas antibody (EpCAM) conjugation facilitated target labeling and flow cytometric sorting of circulating tumor cells. The GSH-coated quantum dots provide a durable, low-toxicity substitute for conventional fluorophores in cellular imaging and cancer cell identification.