Electrochemical detection of protein kinases with methylene blue-functionalized Zr-based metal-organic frameworks as signal labels

Protein kinases play a vital regulatory role in various biological processes. In this work, we developed an electrochemical biosensor for the detection of protein kinases using methylene blue (MB)-functionalized Zr-based metal-organic frameworks (MOFs, UiO-66-NH2) as the signal labels. The results of UV-Vis spectroscopy, X-ray diffraction and N2 adsorption-desorption experiments confirmed the successful encapsulation of MB into UiO-66NH2. The phosphate groups in phosphorylated peptides were recognized by UiO-66-NH2 via the robust coordination with Zr-O clusters on the surface of MOFs. The encapsulated MB molecules in UiO-66-NH2 produced a strong electrochemical signal for highly sensitive detection of protein kinases, which was recorded by square wave voltammetry (SWV). With protein kinase A (PKA) as a model target, the biosensor achieved a detection limit of 0.02 U/mL and a linear range from 0.05 to 20 U/mL. The proposed biosensor was utilized to screen potential inhibitors and determine PKA in serum samples with satisfactory results. This work provided an effective strategy for electrochemical assays of phosphorylation-related biological events in clinical diagnosis.