A label-free photoelectrochemical biosensor with near-zero-background noise for protein kinase A activity assay based on porous ZrO2/CdS octahedra

Herein, porous ZrO2 octahedra with uniform size and large surface area were synthesized by direct calcination of zirconium-based metal-organic frameworks (UiO-66) and its photoelectric properties were enhanced by modification with CdS nanoparticles. Based on porous ZrO2/CdS octahedra, a label-free and sensitive photoelectrochemical (PEC) biosensor with near-zero-background noise was proposed for protein kinase A (PKA) activity assay. The PKA-specific peptide was immobilized on the gold nanoparticles-modified indium tin oxide electrode through its cysteine end. With the participation of adenosine triphosphate (ATP), the peptide phosphorylation was catalyzed by PKA and the ZrO2/CdS octahedra were introduced to the electrode via Zr-O-P coordination between ZrO2 and phosphate group on the phosphorylated peptide. Under visible light irradiation, a large anodic photocurrent generated. The developed PEC biosensor had good analytical characteristics for PKA activity assay: near-zero background noise, wide linear range (0.001−100 U mL−1) and low detection limit (0.00035 U mL−1). This strategy provides an efficient avenue for PKA activity assay, and shows great potential application in diagnostics and drug discovery of PKA-related diseases. Moreover, the developed porous ZrO2/CdS octahedra may have a wider application in PEC monitoring of phosphorylation-dephosphorylation processes of proteins and fast PEC assay of organophosphorus pesticides.