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.