Introduction:

DNA field effect transistor (DNAFET) and RNA field effect transistor (RNAFET) are very useful semiconductor devices for detection of DNA and RNA viruses respectively. Sometime these electronic devices are known as BioFET. Using DNAFET and RNAFET one can design biosensor for detecting deoxyribonucleic acid, ribonucleic acid and protein molecules. After detection one can investigate the nature of detected virus.

DNA and RNA virus:

The most commonly known DNA viruses are Herpes Virus, Hepatitis B virus, Adeno virus, Pox virus and so on whereas most commonly known RNA virus are Rubella virus, Ebola virus, HIV, SERS virus, SARS COV-2 (COVID-19) virus etc.

The whole world is suffering due to outbreak of COVID-19 pandemic and all the daily activities have been disrupted due to this.

As per the research paper published in Indian Journal of medical research by ICMR(Indian council Of Medical Research) there are eleven different types of SARS(Severe Acute Respiratory Syndrome) COV2 virus namely O or ancestral type of virus that was originated from Wuhan, China, reported in December,2019, A2, A2O, A3, B, B1 and so on.

There are four types of deoxynucleotide base:

• DATP (Deoxy Adenosine Triphosphate)
• DCTP (Deoxy Cytidine Triphosphate)
• DGTP (Deoxy Guanosine Triphosphate)
• DTTP (Deoxy Thymidine Triphosphate)

Unlike DNA, RNA is found as a single helix structure. In RNA, four different bases are:

• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Uracil (U)

and base-pair (BP) between A-U and G-C, the three bases A, G and C are also found in DNA but Uracil is replaced by thymidine (G-C and A-T for DNA). The main function of RNA is to carry information of amino acid sequence.

Biosensor design:

Gold has a very good chemical afficinity with nucleic acid and protein molecules which is used to immobilize DNA, RNA and protein molecules. Instead of using Au one can use Pt as for detection of biomolecule. This biosensor will be fabricated as MODFET structure where DNA and RNA potential molecules will be detected by measuring the variation of biomolecular changes of capacitance and charges. DNA and RNA virus will be detected by both in situ and ex-situ measurements of 2D-EG (2D-Electron Gas) change also one can measure the change in threshold voltage to detect the base sequence of DNA and RNA virus.

Using iterative process of multiple-base or single-base extension one can measure the change in electron density as well as threshold voltage. The intrinsic charges generated by DNA and RNA virus can be transduced into proportional electrical charges with the help of MODFET biosensor.

Each of dATP, dCTP, dGTP and dTTP which generate a different 2D-EG. This change in charge carrier can be measured as a change in threshold voltage of MODFET biosensor. For DNA virus as electrostatic charge in DNA molecule interact with 2D-EG through the spacer layer of MODFET biosensor.

Conclusion: Applications of MODFET biosensor

Multi gate or single gate GaN-AlGaN MODFET biosensor is useful for real time detection of COVID-19. Recent COVID-19 pandemic the most useful diagnostic method Reverse Transcription Polymerase Chain Reaction (RT-PCR) which having longer detection time but one can detect COVID-19 virus using MODFET biosensor with shorter time of detection. So this biosensor is an alternative way for rapid and accurate detection of COVID-19. The advantages of biosensor include low cost and quick detection.