Evaluation of the biocompatibility of the GSH-coated Ag2S quantum dots in vitro: a perfect example for the non-toxic optical probes

Near-infrared quantum dots (NIR QDs) are promising candidate for the fluorescent probes due to their better penetration depth, long-lived luminescence with size-tunable photoluminescence wavelengths. Glutathione-coated silver sulfide quantum dots (GSH-Ag₂S QDs) were synthesized using AgNO₃ and Na₂S in the aqueous media and they can give reaction with glutathione reductase (GR) and glutathione-s transferase (GST) enzymes as acting substrate analogue in vitro. Investigation of the toxicity of the nanomaterials are necessary to use them in the medical field and biomedical applications. Thus, in this study we investigated biocompatibility of the GSH-Ag₂S QDs in vitro using 293 T and CFPAC-1 cell lines. Cell viability by MTT assay, light microscopy, fluorescence microscopy, oxidative stress enzyme activities and ICP-MS analysis were performed to evaluate the cytotoxicity and internalization of the GSH-Ag₂S QDs. GSH-Ag₂S QDs showed great biocompatibility with both cell lines and did not cause imbalance in the oxidative stress metabolism. The ultralow solubility product constant of Ag₂S QDs (K_sp = 6.3 × 10^-50) prevents release of Ag ions into the biological systems that is in agreement with data obtained by ICP-MS. In conclusion, this data prove potential of GSH-Ag₂S QDs as a biocompatible optical probe to be used for the detection and/or targeting of GSH impaired diseases including cancer.