Biosensors short-term stability

Even with a simple first generation biosensor, working in amperometric mode at a fixed detection potential of +0.7 V (high enough to directly oxidize H2O2 at the electrode surface), it is possible to achieve a linearity between 1 and 9 x 10 M (R = 0.9997) with a sensitivity of 1.11 pAmM (rsd% = 0.97%) and a limit of detection between 2.5 x 10 M (calculated as S/N = 3). Short-term stability was excellent as shown in Figure 13.19. Longterm stability results in a decrease of 34% after one month of continuous use. 

Even before the introduction of miniaturized biosensor arrays, however, some systems able to simultaneously measure glucose and lactate had been reported in the literature. One example is provided by Osborne et al. [157], who described plastic film carbon electrodes fabricated in a split-disk configuration and then modified to obtain a dual biosensor. They achieved a continuous monitoring of these metabolites by placing the dual electrode in a thin-layer radial flow cell coupled to a microdialysis probe. The stability of the sensors was sufficient for short-term in vivo experiments in which the crosstalk, i.e., the percentage of current measured by one biosensor but due to product generated by the partner biosensor, was acceptable for an in vivo application. 

In this chapter, the focus is laid on biosensor principles and a short introduction into hydrogels as immobilization matrix for enzymes is given. Measurement methods for investigating the long-term stability of used enzymes will be presented and finally smart applications of hydrogels combining sensor and therapeutic attributes will be discussed. 

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