Analytical Sciences

L-Cysteine-capped CdTe Quantum Dots as a Fluorescence Probe for Determination of Cardiolipin

Wenfeng ZHAO,* Yingsing FUNG,* Waisum O,** and M. P. L. CHEUNG**

*Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China
**Department of Anatomy, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China

This paper described the investigation of surface-modified quantum dots (QDs) as a fluorescence probe for the detection of cardiolipin. A single-step method for preparation of non-toxic and photo-stable cadmium telluride (CdTe) QDs capped by L-cysteine in aqueous solution was developed. The prepared QDs were characterized by high-resolution transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry and spectrofluorometry. These functional QDs were used as a fluorescence probe for cardiolipin determination based on the fluorescence quenching. The optimum fluorescence intensity was found to be at pH 7.4 with QDs concentration of 4 × 10⁻⁵ mol L⁻¹. The effect of other phospholipids on the intensity of CdTe QDs showed a low interference response. Under optimized conditions, the quenched fluorescence intensity was linear with the concentration of cardiolipin in the range of 1.33 × 10⁻⁷ − 10.4 × 10⁻⁷ mol L⁻¹ (r = 0.9976) and a detection limit (S/N = 3) of 18.5 nmol L⁻¹. The proposed method was applied to the determination of cardiolipin content of HepG2 cell samples before and after oxidative stress with satisfactory results.

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