Photoelectrochemical biosensor for protein kinase A detection based on carbon microspheres, peptide functionalized Au-ZIF-8 and TiO2/g-C3N4

In this work, a novel and sensitive photoelectrochemical (PEC) strategy was designed for protein kinase A (PKA) detection, comprising carbon microsphere (CMS) modified ITO electrode, TiO 2 as the phosphate group recognition material and graphite-carbon nitride (g-C 3 N 4 ) as photoactive material. For the first time, gold nanoparticle decorated zeolitic imidazolate frameworks (Au-ZIF-8) was employed to fabricate biosensor for PKA activity assay with the function of substrate peptide immobilization and signal amplification. Firstly, substrate peptides were assembled on the Au-ZIF-8/CMS/ITO surface through the covalent bonding between the gold nanoparticles (AuNPs) and sulfydryl groups of the peptides. Then, in the presence of ATP , phosphorylation of the substrate peptide was achieved under PKA catalysis. Finally, TiO 2 -g-C 3 N 4 composites were further modified on the electrode surface based on bonding between TiO 2 and phosphate groups created via phosphorylation of the peptide (yielding TiO 2 -g-C 3 N 4 /P-peptide/Au-ZIF-8/CMS/ITO), which is different with our previous work by directly immobilizing g-C 3 N 4 composite on electrode surface. The developed method showed a wide linear range from 0.05–50 U mL −1 . The detection limit was 0.02 U mL −1 (S/N = 3). The constructed biosensor exhibited high detection specificity for PKA. In addition, the wide applicability of this biosensor was demonstrated by evaluating the inhibition ability of ellagic acid towards PKA.