Fluorescence-based CdTe nanosensor for sensitive detection of cytochrome C

Cytochrome c (Cyt c) is commonly used as intrinsic biomarker for several characteristics of the cell such as respiration, energy level and apoptosis. In the present study a simple colorimetric sensor should be developed and tested for the real-time detection of Cyt c in living cells. We synthesized cadmium telluride quantum dots (CdTe QDs) capped with thioglycolic acid (TGA) as a fluorometric Cyt c nanosensor. The synthesized TGA/CdTe QDs nanosensor was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and absorption as well as fluorescence spectrophotometry. We investigated the developed TGA/CdTe QDs sensor with regard to its applicability in the fluorometric detection of Cyt c. Results showed that the TGA/CdTe QDs could be used as a sensitive fluorescence probe for the quantification of different concentrations of Cyt c ranging from 0.5 − 2.5 μM. Increased binding of QDs to Cyt c results in decreasing fluorescence. The fluorescence of the QDs is inversely correlated to the Cyt c concentration. Based on these data, a standard curve up to 2.5 μM Cyt c was established. Moreover, the developed nanosensor was applied in different concentrations on primary human dermal fibroblasts. Results showed that TGA/CdTe QDs were taken up by cells and could be visualized by fluorescence microscopy. Quantification of Cyt c within living cells via QDs is, however, influenced by various factors such as cell damage, QD aggregation or the level of reactive oxygen species, which have to be taken into account.