The assessment of potentially interfering metabolites and dietary components in blood using an osmotic glucose sensor based on the concanavalin A-dextran affinity assay.

Continuous surveillance of blood glucose is a prerogative of maintaining a tight glycaemic control in people suffering from diabetes mellitus. Implantable sensor technology offers the potential of conducting direct long term continuous glucose measurements, but current size restrictions and operational challenges have limited their applications. The osmotic sensor utilises diffusion to create a hydrostatic pressure that is independent of sensor operation and power consumption. This permits ultra-low power architectures to be realized with a minimal start-up time in a package suitable for miniaturization. In contrast, osmotic sensors suffer from the inability of their membranes to discriminate between different constituents in blood or the interstitial fluid that are of comparable size to glucose. By implementing an affinity assay based on the competitive bonding between concanavalin A and dextran, the selectivity of the membrane can be transferred to the glucose specific recognition of the affinity assay. The osmotic effect from the physiological levels of several key metabolites and nutritional components has been addressed identifying in particular ethanol, lactate and amino acids as potential interfering constituents. Both ascorbic acid and mannose would have a normal physiological concentration that is too low to be detected. The studies shows that an osmotic glucose sensor equipped with the con A-dextran affinity assay, is able to filter out potential interfering constituents present in blood, plasma and the interstitial fluid yet retaining a pressure that is proportional to glucose only.