Personal glucose meter-based portable method for creatine kinase assay

We herein developed a simple and label-free method to detect the creatine kinase (CK) activity by employing a personal glucose meter (PGM) as a detection device. This method relies on the target-induced consumption of glucose by the cascade enzymatic reaction (CER) promoted by the combined activities of CK and hexokinase (HK). The target CK first catalyzes the phosphorylation of adenosine 5′-diphosphate (ADP) to adenosine 5′-triphosphate (ATP) using creatine phosphate (CP) as a phosphate donor. HK then phosphorylates glucose into glucose-6-phosphate by converting the produced ATP back to ADP, which could enter another cycle of the CER to further phosphorylate glucose in a sample. As a consequence, the glucose level would decrease depending on the CK activity, which could be very conveniently detected using a PGM. With this unique design principle, we successfully determined the CK activity down to 0.0147 U/mL with high specificity against various non-target enzymes. We also verified that the developed strategy can reliably detect CK activity in heterogeneous human blood, ensuring its robust utility in various clinical applications. This user-friendly method enables point-of care detection of CK, offering a practical tool for monitoring muscle health. By allowing simultaneous tracking of CK and glucose levels with the same PGM device, this approach is particularly beneficial for diabetes mellitus (DM) patients, empowering them to proactively manage their health and reduce the risk of muscle-related complications.