Analytical Applications of Enzymatic Growth of Quantum Dots

Abstract

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 H(2)S, 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 H(2)S, which instantly reacts with Cd(2+) 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.

Organophosphorus acid anhydrolase bio-template for the synthesis of CdS quantum dots

“…2,3 Synthesis of dual functional bioinorganic hybrid nanostructures directed by active enzymes remains little explored. 5 Here, we report a direct synthesis of CdS quantum dots within enzyme matrix conjugated with OPAA enzyme. Pairing these semiconducting probes with intact and active enzymes opens the doors to understanding the mechanisms of many previously unknown bioprocesses.…”

Nanomaterials for Sensing and Destroying Pesticides

“…48 Thiol-containing molecules (in this case, thiocholine) promote the decomposition of S 2 O 3 2− to H 2 S, which, in the presence of Cd 2+ ions, forms fluorescent nanocrystals of CdS. Formation of these fluorescent nanoparticles is monitored by fluorescence spectroscopy.…”

Enzymatic Growth of Metal and Semiconductor Nanoparticles in Bioanalysis

“…The drawback of the systems based on the enzymatic generation of metallic NPs is that only UV–vis spectroscopy and electrochemistry can be utilized for reading of a signal. Bioanalytical enzymatic systems producing fluorescent NPs can employ much more sensitive techniques such as fluorescence spectroscopy or photoelectrochemistry to register the read out signal as demonstrated in the seminal work . Two analytical assays for detection of enzymatic activities in which generation of fluorescent CdS NPs was induced by products of bio‐catalytic reactions were reported.…”

“…B) TEM image of the CdS QDs formed in the presence of ALP (228 ng mL −1 ), sodium thiophosphate (75 × 10 −6 m ) and Cd(NO 3 ) 2 (2.5 × 10 −3 m ). Reproduced with permission …”