polymer blend of PEDOT:PSS-based electrochemical transistors as ions (NaCl, KCl, and

CaCl2) level detector. In this study, they demonstrated highly sensitive organic electro­

chemical transistors sensors with a low LOD of 1 mM for different soluble ionic

compound-based electrolytes and high sensitivities 650 and 200 mV/dec for Na⁺ ions in

the electrolyte range of 1–100 mM and 100–1,000 mM.

In addition, in 2017, Damiati et al. presented the fabrication of anti-CD133 antibody/

S-layer fusion protein (rSbpA/ZZ lattice)/Au-based electrodes and electrochemical

properties of efficient acoustic 3D-printed electrochemical biosensors for the real-time

immunodetection of liver cancer cells (HepG2) for the detection of the tumor biomarker

CD133 [16]. Moreover, in 2018, Zhang et al. fabricated a novel ultrasensitive and selective

biosensor for the detection of ascorbic acid using a combination of an organic transistor

and a molecularly imprinted polymer (MIP)–modified gate in a wide ascorbic acid con­

centration range from 1 μM to 100 μM [17]. The electrochemical results showed that the

novel MIP-OECT biosensor had a low LOD of 10 nM (S/N > 3) and high sensitivity of

75.3 μA for target analyte (ascorbic acid) in the presences of different analytes such

as glucose, aspartic acid, uric acid, glutathione, glycine, metal ions (K⁺, Na⁺, Ca²⁺, Mg²⁺,

and Fe²⁺), and H2O2.

10.2 Electrochemical Properties of Bio-Organic Transistors

The use of bio-based nanostructures in preparation of enzymatic/non-enzymatic elec­

trochemical biosensors act as new types of medical devices for detecting and quantifying

cancer biomarkers and are advantageous with sensitive early detection, high selectivity,

accurate, rapid, and low LOD. To improve the sensitivity and selectivity of biosensors, a

variety of green signal amplification strategies have been studied, such as the use of

metal/metal oxide nanoparticles (NPs), graphene/graphene oxide (GO), carbon nano­

tubes (CNTs), fullerenes, and biopolymers. Depending on the synergistic effects of tar­

geted analytes and bio-nanostructures used, different electrochemical biosensors can be

examined using different detection measurement strategies such as potentiometric, am­

perometric, conductometric, voltammetric, and colorimetric change. These bio-based

electrochemical sensors have been shown very low LODs for targeted biomarkers and

molecules such as drugs, dyes, toxic substances, pathogens, viruses, heavy metals, DNA,

RNA, pesticides, antibodies, small molecules, cancer cells, and human proteins over a

wide concentration range. However, electrochemical biosensors must have still specific

limitations such as industrial production, the integration of a biosensor’s components and

deficiency of multi-step strategies, insufficient clinical trial data, an insufficient number of

experts on nanotechnology applications.

To overcome these issues, several scientists and researchers have studied the pre­

paration and experimental research of advanced electrochemical biosensors and nano-

biosensors with high affinity targeted molecules, high-performance electrodes, and

efficient signal transferring in recent studies. Among several types of nanostructures used

in the modification of the surface of electrodes, Zheng et al. in 2021 produced a novel

effective peptide–antibody sandwich electrochemical biosensor using metallic AuPt na­

noparticle and manganese dioxide (MnO2) – functionalized covalent organic frameworks

(AuPt@MnO2@COF) for the detection of prostate-specific antigen (PSA). The biosensing

mechanism was based on the redox signal of methylene blue (MB) and experimental

160

Bioelectronics