Enzyme solutions were applied on hydrophilic regions of substrate
comprising titania by inkjet printer. After printing, the samples were
exposed to drying, the sensitive area remained colorless. Then we tested
the sensitivity of the method on specific substrates reacting with
oxidases contained in the test zone of printed biosensors.
In the case of glucose sensor we used aqueous solutions of glucose with
concentrations from 3 to 100 mg / dL, while in the case of cholesterol
biosensor it was alcoholic cholesterol solution with concentrations from
6 to 200 mg / dL.
As shown in the Figure 5, as a result of testing in both cases, we
observed the relationship between the intensity of color and the
concentration of substrate (glucose, cholesterol).
The graph shows that with the increasing concentration of glucose and
cholesterol, the gradual saturation of the color has the shape of
exponential dependence. This indicates the reaction according to the law
of Lambert-Bouguer-Beer law29 for the colored
solutions, when the intensity of the emitted light passing through the
solution is reduced exponentially depending on the optical density of
the substance.