Analytical Applications of Enzymatic Growth of Quantum Dots

• Published in: Chemistry : a European journal Vol. 16; no. 21; pp. 6187 - 6192
• Main Authors: Saa, Laura, Virel, Ana, Sanchez-Lopez, Jose, Pavlov, Valery
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-06-2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Acetylcholinesterase - metabolism; Alkaline phosphatase; Alkaline Phosphatase - metabolism; Assaying; Biocatalysis; Cadmium; Cadmium Compounds - chemistry; Cadmium sulfides; Chemistry; emission spectroscopy; enzyme catalysis; Enzymes; Esterases; Fluorescence; Hydrogen Sulfide - metabolism; Mathematical analysis; Phosphatase; Quantum Dots; semiconductors; Sulfates - chemistry
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.200903373

We have developed an analytical assay to detect the enzymatic activity of acetylcholine esterase and alkaline phosphatase based on the generation of quantum dots by enzymatic products. Acetylcholine esterase converts acetylthiocholine into thiocholine. The latter enhances the rate of decomposition of sodium thiosulfate into H2S, which in the presence of cadmium sulfate yields CdS quantum dots showing a time dependent exponential growth, typical of autocatalytic processes. This assay was also applied to detect acetylcholine esterase inhibitors. Alkaline phosphatase hydrolyzes thiophosphate and yields H2S, which instantly reacts with Cd2+ to give CdS quantum dots. The formation of CdS quantum dots in both reactions was followed by fluorescence spectroscopy and showed dependence on the concentration of enzyme and substrate.
Dot products: We have developed two analytical assays for enzymatic activity based on the generation of quantum dots from enzymatic products. These assays were applied to the detection of acetylcholine esterase and alkaline phosphatase. These enzymes induce the formation of H2S, which in the presence of cadmium cations yields CdS quantum dots.