SUITABILITY OF AQUEOUS DISPERSIONS OF DEXTRAN AND CONCANAVALIN-A FOR GLUCOSE SENSING IN DIFFERENT VARIANTS OF THE AFFINITY SENSOR

Aqueous dispersions of dextran and Concanvalin A (Con A) were investigated for possible application as the essential part of a glucose affinity sensor. The considered variants of signal formation were based on the sugar-dependent dissociation of Con A and dextran, which were enclosed in a small dialysis chamber with a membrane permeable to sugars but not to macromolecules. Two alternative proposals were investigated: (a) determination of the concentration of dissolved labelled lectin in equilibrium with a lectin fraction bound to cross-linked dextran or (b) determination of the viscosity of an homogeneous dextran-lectin dispersion. For both approaches, suitable conditions were established to give a strong dependence of the measured parameter on the glucose concentration in a concentration range relevant for blood sugar sensing. Both glucose-dependent Con A distribution and glucose-dependent viscosity changes of the dextran/Con A solution showed a sufficiently fast response (<2 min) to a change in the glucose concentration. The long term stability of the lectin, with respect to binding to dextran and its influence on the viscosity of a concentrated solution of high molecular weight dextran, was remarkable.