Ion track-based urea sensing

A highly sensitive urea biosensor is described. We employed polymer foils which are thin, swift heavy ion-irradiated polycarbonate foils, followed by etching. The examined geometrical arrangement is of 1 foil, two compartments system. One electrode is placed in each compartment and a sinusoidal voltage is applied to the system. The enzyme urease is attached to the inner walls of the etched ion tracks in the foil, and one of the compartments is filled with urea solution of variable concentrations which can then interact with the enzyme, resulting in a change of track resistance. These results are compared with those obtained using a simple, non-confined urea/urease mixture. We report that this strategy, where the enzyme is bound to the etched track walls, is very efficient, as it demonstrates very high sensitivity. In this system, urea can be detected at a concentration as low as 1 × 10^-7 M. The sensor is, moreover, still active at a concentration of 1 M urea. The currents associated with each concentration differ by a factor of 10.