Development of a miniaturized glucose monitor for whole blood measurements

The glucose concentration in diluted whole blood has been measured, using a miniaturized thermal biosensor based on the enzyme thermistor principle. The biosensor is a small flow-injection system. A sample volume of 20μ1 is injected into a flow of 50μl/min. The heat produced when the sample passes the enzyme column is measured with a thermistor connected to a Wheatstone bridge. The enzyme column contains glucose oxidase and catalase co-immobilized on a solid support material. Samples of whole blood usually cause problems in flowsystems. The blood cells tend to block the enzyme column and the back pressure increases. We have tested a superporous agarose material as enzyme support material using ten-fold diluted samples of whole human blood. The blood was collected from the finger-tip and diluted with buffer containing an anticoagulant and sodium fluoride. The number of samples possible to inject and the accuracy compared to the Boehringer Mannheim Reflolux have been determined. At least 100 ten-fold diluted blood samples could be injected on a micro-column of superporous agarose. The obtained glucose concentration correlated well with the one obtained with the Boehringer Mannheim Reflolux