oa An Organic Field Effect Transistor Based Nano Biosensor for the Early Detection of Cardio Vascular Disease – The Most Common Death Causing Disease in Qatar

Qatar has one of the world's fastest growing population. The lifestyle and socio-economic situation of the Qatar, like other Arab countries are also vastly changing according to the growing trends. These changes finally reflected in the life expectancy and led to a rise in the “Non-Communicable diseases” or otherwise known as the diseases of longevity like Cancer, Cardio Vascular Diseases (CVD), Diabetes Mellitus (DM), Asthma, Liver Cirrhosis etc. According to the data of Qatar Health Report of the year 2012, Coronary Heart Disease is one of the most common causes of death in Qatar after road traffic accidents [1]. It is the foremost cause of death universally, demonstrating 30 percent and in Qatar it is 13.65 %. Cardio Vascular Disease is not considered as a solitary condition, but it is a collection of diverse conditions that affect both heart and blood carrying vessels. There are many biomarkers which are currently used for the detection of CVD in the early stage. C-reactive protein (CRP) is one among them which is seen in blood plasma which in turn is produced in the hepatocytes of liver. The synthesis of CRP is initiated due to the inflammation response from fat cells and macrophages. The clinical significance of CRP is that it is considered as one of the best authenticated biomarker for Cardio Vascular Diseases.

Organic electronics have established into a sensational area of technology and research to substitute typical inorganic semiconductors. Out of that Organic Field Effect Transistor (OFET) have found new uses in the area of biosensors. OFET biosensors mainly use π-conjugated organic semiconductors as electronic materials which is encapsulated with a biological component which can be either antibodies, DNA, enzymes, proteins or bacteria. These are mainly due to their low manufacturing cost when compared to the traditional diagnosing techniques and faster response time. Another advantage of OTFT biosensors over other sensing techniques are the possibility of miniaturization and the output can be delivered in simple electronic form [2]. The biological component can be incorporated in to the active layer and when a source-drain voltage is supplied, the antibody/antigen binding behavior acts as a resistor in the circuit which will be a current flow as a result of charge carrier transport with respect to the corresponding biological or chemical reaction, which can be calculated and displayed. A linear rise in the drain current of the OFET devise can be observed in proportional to the concentration of the biological component [3]. The response time may vary from 10 to 20 seconds.

In this article we are demonstrating an OFET biosensor for the detection of C-reactive protein using antigen-antibody reaction. The biological component will be encapsulated inside the buffer layer of OFET which is spin coated using poly(3,4-ethylenedioxythiophene–poly(styrene-sulfonate) (PEDOT:PSS). The entrapment process is done by electrochemical polymerization. The device is fabricated in such a way that the antigen-antibody reaction will alter the electron flow of the OFET which can be attributed to the concentration of the C-reactive protein. This will in turn change the characteristic current-voltage produced which is measured using a Keithley electrical measurement system. A linear rise in the OTFT drain current may be observed with proportional to the amount of CRP-Anti CRP complex, which is further calculated and displayed in the form of digits.

References

1. Qatar Health Report of the year 2012.

2. Danesh, J., et al., C-Reactive Protein and Other Circulating Markers of Inflammation in the Prediction of Coronary Heart Disease. New England Journal of Medicine, 2004. 1387 p.

3. Maddalena F. Organic field-effect transistors for sensing applications. Groningen: s.n., 2011. 110 p.