Sui Chengji,Liu Fei,Tang Lihua,Li Xue,Zhou Yunlei,Yin Huanshun,Ai Shiyun
A sensitive and selective photoelectrochemical (PEC) method is described for the detection of protein kinase A (PKA) activity based on the use of graphite-like carbon nitride (g-C 3 N 4 ) and the CdS quantum dots (QDs). Firstly, a complex was synthesized from g-C 3 N 4 and gold nanoparticles (AuNPs). It was employed as both the PEC-active material and as a support for immobilization of peptides. The latter were assembled on an ITO electrode modified with g-C 3 N 4 -AuNPs and subsequently phosphorylated by PKA in the presence of adenosine 5′-[γ-thio]triphosphate (ATP-S). Finally, CdS quantum dots (QDs) were introduced on the ITO in order to increase the PEC response of g-C 3 N 4 based on the Cd-S binding between the QDs and thiol groups. Under the optimal conditions and a typical working voltage of −0.3 V, the method has a dynamic range that extends from 0.05 to 50 unit·mL −1 , with a 0.017 unit·mL −1 lower detection limit. The method was successfully applied to the quantification of the inhibitory effect of ellagic acid on the activity of PKA, and to monitor enzyme activity in cell lysates.
Schematic of a sensitive and selective photoelectrochemical biosensor for the detection of protein kinase A activity. It is based on the use of graphite-like carbon nitride and CdS quantum dots.
Wang Mo,Yang Zhiqing,Guo Yunlong,Wang Xinxu,Yin Huanshun,Ai Shiyun
We demonstrate a photo-electrochemical biosensor for the sensitive and specific detection of microRNA using Bi 2 S 3 nanorods as a photoactive material and streptavidin as the unit that inhibits photocurrent. Bi 2 S 3 nanorods were synthesized hydrothermally in organic phase and displayed excellent light-to-current conversion efficiency. The Bi 2 S 3 was deposited on an indium tin oxide (ITO) slice and then modified with gold nanoparticles onto which biotinylated hairpin probe DNA was deposited as a monolayer. Following hybridization between the biotinylated probe DNA and the target microRNA, the stem-loop structure of the probe DNA was unfolded and the biotin directed outwards into the solution. Streptavidin was then added to bind to biotin via the strong streptavidin-biotin interactions. This causes the photocurrent of the modified ITO to decrease due to steric hindrance that blocks the transfer of electrons from added ascorbic acid to the surface of the electrode. The method has a detection limit as low as 3.5 fM of microRNA and can excellently discriminate even singly mismatched microRNA. The method was successfully applied to investigate the effect of abscisic acid on the expression level of microRNA-159a in seeds of Arabidopsis thaliana . We conclude that the assay presented here has a large potential as a method for quantification of microRNA and for studying the epigenetic regulation of flowering plants.
The photocurrent generation and decrease mechanism of the PEC biosensor.
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