Photoelectrochemical determination of the activity of alkaline phosphatase by using a CdS@graphene conjugate coupled to CoOOH nanosheets for signal amplification

Abstract

AbstractA method is described for photoelectrochemical determination of the activity of alkaline phosphatase (ALP). It employs an indium tin oxide (ITO) electrode modified a CdS quantum dots@graphene (CdS@GR) composite and hexagonal cobalt oxyhydroxide (CoOOH) nanosheets. The CdS@GR nanocomposite was synthesized by assembling the CdS quantum dots onto a GO film to receive a basic photocurrent response of the ITO. This is further improved by covering it with CoOOH nanosheets. Secondly, 2-phospho-L-ascorbic acid (AAP) is added as a substrate for ALP. Its hydrolysis yields ascorbic acid which reduces CoOOH to form cobalt(II) ion. As a result, the CoOOH nanosheets decompose. This is accompanied by a reduction of the photocurrent. The effect was used to design a selective and sensitive assay of determination of the activity of ALP. Under the optimized experimental conditions, response is linear in the 10 to 300\xa0U·L−1ALP activity range. The detection limit is 1.5\xa0U·L−1 at a signal-to-noise ratio of 3.\n Graphical abstractIndium tin oxide (ITO) was coted with\xa0CdS@graphene and\xa0CoOOH to obtain a material with superior photoelectrochemical properties. The detection of alkaline phosphatase (ALP) was accomplished by using 2-phospho-L-ascorbic acid (AAP) which is\xa0hydrolyzed by ALP to release\xa0ascorbic acid (AA) which reduces CoOOH to Co2+.