Portable and sensitive detection of protein kinase activity by using commercial personal glucose meter

Protein kinases (PKs), which play critical regulatory roles in the cellular signal transduction pathways, have been regarded as important molecular targets for clinical diagnosis as well as pharmaceutical development. Most of the existing PK assays rely heavily on the use of expensive and sophisticated instruments, which are only available in specialized labs. Herein we wish to report a new sensing strategy for portable and sensitive detection of PK activity by use of a commercial personal glucose meter (PGM) for signal readout with the assistance of Zr4+-functionalized magnetic beads (ZrMBs). In this design, ZrMBs can selectively capture PK-induced biotin-phosphopeptide substrate against the unphosphorylated ones. Streptavidin (STV) acts as a bridge to further bring biotin-invertase onto the surface of ZrMBs in correlation with the amount of immobilized biotin-phosphopeptides. Finally, the anchored invertase on the ZrMBs can catalyze the hydrolysis of sucrose to glucose with millions of turnover, which is monitored by the PGM with amplified signal. Although only common PGM is used for signal readout, as low as 0.0001 U/mu L protein kinase A (PKA) can be clearly detectable in this study and the sensitivity is well comparable to those assays by using large-scale equipment. Therefore, due to the distinct features of PGM such as low cost, simple operation, wide accessibility and portability, this proposed assay shows great potential for the point-of-care testing of PKs activities in the future.