A new handheld biosensor for monitoring blood ketones

A disposable amperometric biosensor for monitoring the blood ketones has been developed. It can be used to determine the concentration of β-hydroxybutyrate without pretreatment of blood samples. Enzymes are immobilized on screen-printed carbon electrodes. For immobilizing the enzymes, first a layer of hydrophilic gel CMC was printed on the screen-printed carbon electrodes. β-Hydroxybutyrate dehydrogenase, cofactor NAD and electron transfer mediator, potassium ferricyanide are immobilized on the electrode surface by adsorption. Experimentally the compositions of β-hydroxybutyrate dehydrogenase, potassium ferricyanide, NAD and other components are optimized. Amperometry performed by a handheld meter is used for the determination of β-hydroxybutyrate concentration. Two microliters of whole blood or serum is needed for one test, and the response time of the sensor is 50 s. Experimental results show that the responses of the sensors have relevant good linearity in the range 1.5-550 mg L−1. The testing results by the biosensors and the routine hospital blood analyzer are agreed closely.