photolithography technique. The hydrophilic region of the counter and reference elec­

trodes was subjected to aldehyde treatment to functionalize them. A working electrode

modified with Prussian blue redox mediator combined with a base of reduced graphene

oxide (composite) was used as an electron transfer medium. Glucose oxidase enzyme was

immobilized over this matrix and glucose sensing was done. A linear range of 0.1–25 mM

and a limit of detection (LoD) was 25 µM. In further, the same electrode was able to sense

hydrogen peroxide which was the by-product of the enzyme-substrate reaction. To check

the practicality in real time, human blood and urine samples were used for the detection

of glucose. To validate, this printable sensor was compared with the market glucose

meter and appreciable results were seen [20]. Similarly, a paper-based biosensor with

glucose oxidase and horseradish peroxide composite with copper nanostructure matrix

was reported by Zhu et al. A wax printing approach was used here. These copper na­

nostructures were inorganic, flower-like crystals that improved the co-immobilization of

both enzymes. This provided stability to the enzyme activity and enhanced the electron

FIGURE 22.6

Reprint of the devices (a) adapted with permission from Reference [ 15] Copyright (2018), IEEE. (b) Adapted with

permission [ 16], Copyright (2020), ACS. (c) Adapted with permission [ 17], Copyright (2020), IEEE. (d) Adapted

with permission [ 18], Copyright (2021), IEEE. (e) Adapted with permission [ 19], Copyright (2021), IEEE.

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Bioelectronics