Engineering PQQ-glucose dehydrogenase into an allosteric electrochemical Ca2+ sensor

Electrochemical biosensors convert biological events to an electrical current. To date most electrochemical biosensors exploit activities of naturally occurring enzymes. Here we demonstrated that insertion of a calmodulin domain into the redox enzyme PQQ-glucose dehydrogenase resulted in a selective Ca2+ biosensor that could be used to rapidly measure Ca2+ concentrations in human biological fluids. We were able to convert a point-of-care glucometer into Ca2+ monitor by refurbishing it with the developed biosensor. We propose that similar engineering strategies may be used to create highly specific electrochemical biosensors to other analytes. Compatibility with cheap and ubiquitous amperometric detectors is expected to accelerate progression of these biosensors into clinical applications.