Modulating the growth of cysteine-capped cadmium sulfide quantum dots with enzymatically produced hydrogen peroxide

Ruta Grinyte,Valeri Pavlov,Laura Saa,Javier Barroso

doi:10.1007/s12274-016-1378-1

Abstract

Cysteine (CSH) readily stabilizes cadmium sulfide quantum dots (CdS QDs) that grow in aqueous buffered solutions. The oxidation of CSH by hydrogen peroxide (H2O2) at room temperature yields cystine (CSSC), which is less efficient in stabilizing CdS QDs compared to CSH. Herein, we demonstrate that such oxidation causes a decrease in the formation rate of CSH-capped CdS QDs from Cd2+ and S2− ions. For the first time, we combined the oxidation of CSH with the glucose oxidase (GO x )-assisted biocatalytic oxidation of D-glucose, which leads to a buildup of H2O2 in the reaction mixture. The enzymatically modulated in situ growth of CdS QDs was monitored using two techniques: fluorescence spectroscopy and photoelectrochemical (PEC) analysis. This system enables quantification of GO x and glucose in human serum.

Highlights

The exponential development of nanotechnology during the past decades has enabled the fabrication of new materials and the design of novel biosensing methods
We demonstrate that the oxidation of the CSH stabilizing agent by H2O2 causes a decrease in the formation rate of CSH-capped cadmium sulfide quantum dots (CdS quantum dots (QDs)) from Cd2+ and S2– ions
The formation of fluorescent cadmium sulfide (CdS) QDs was monitored by fluorescence spectroscopy

Summary

Introduction

The exponential development of nanotechnology during the past decades has enabled the fabrication of new materials and the design of novel biosensing methods. A valuable tool that has been employed in biosensing is the use of inorganic nanoparticles (NPs). The optical properties of metal NPs depend on their shapes and sizes [2]. Metal NPs are used in bioanalysis as labels in affinity assays [3,4,5], enhancers of Raman scattering [6,7,8,9], quenchers of fluorescence signal [10, 11], and scaffolds for assembling biorecognition elements [12, 13]. In situ enzymegenerated metal NPs are usually not fluorescent and hardly demonstrate any photocatalytic activities. This drawback limits their use in bioassays

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Conclusion