Low-cost graphite and double-gate FET-based label-free biosensor for dopamine sensing to detect neural diseases.

The manuscript proposes biosensors for detecting different concentrations of neurotransmitters named dopamine, which have a critical role in the human body's neurological, hormonal, and renal systems. In this work, the primary focus is to detect dopamine, whose disorder levels cause many neurological disabilities such as Alzheimer's and Parkinson's disease. In the present work, the simulation of two different structures has been studies: a) a graphite-based structure and b) a double gate TFET structure for detecting dopamine using TCAD Silvaco software. The proposed device utilizes a graphite-based structure with respective work functions of the used materials and studies the change in ON current (I sensing factor is calculated for simulation study for V = 0.8 V). The cavity is increased to 800 µm for graphite-based biosensors for improved sensitivity. The graphite-based biosensors can detect up to 13.3 nM concentration of dopamine. Experimental electrochemical analysis results verify the proposed graphite-based biosensors' sensitivity for different dopamine concentrations. Another double gate field effect transistor (FET) biosensor has also been investigated for the detection of dopamine. The effective dielectric constant has been calculated using Bruggeman's model to check the sensitivity of double gate FET-based sensors for varying dopamine and uric acid concentrations. The sensitivity is increased with the increase of dopamine concentration percentage.