Highly Sensitive Potassium-Doped Polypyrrole/Carbon Nanotube-Based Enzyme Field Effect Transistor (ENFET) for Cholesterol Detection

• Published in: Applied biochemistry and biotechnology 2014-10, Vol.174 (3), p.1104-1114
• Main Authors: Barik, Md. Abdul, Sarma, Manoj Kumar, Sarkar, C. R, Dutta, Jiten Ch
• Format: Article
• Language: English
• Subjects: adsorption; Biochemistry; Biological and medical sciences; Biosensing Techniques; Biotechnology; carbon nanotubes; Chemistry; Chemistry and Materials Science; Cholesterol; Cholesterol - chemistry; Cholesterol - isolation & purification; detection limit; Electrodes; enzyme kinetics; Enzymes; Enzymes, Immobilized; Fundamental and applied biological sciences. Psychology; glass; glucose; graphene; Humans; indium; Indium tin oxides; nanocomposites; Nanotechnology; Nanotubes; Nanotubes, Carbon - chemistry; Polymers - chemistry; potassium; Potassium - chemistry; Pyrroles - chemistry; Sodium chloride; tin; Tin Compounds - chemistry; Urea; uric acid; Zirconium; Zirconium - chemistry
• ISSN: 0273-2289; 1559-0291
• DOI: 10.1007/s12010-014-1029-5

Highly sensitive potassium (K)-doped carbon nanotube (CNT) and polypyrrole (PPy) nanocomposite membrane-based enzyme field effect transistor (ENFET) has been fabricated on indium tin oxide (ITO) for detection of cholesterol. P-type graphene has been deposited as substrate on ITO glass electrochemically. N-type graphene has been deposited in source and drain regions. Zirconium dioxide (ZrO₂) has been deposited on the channel region as gate insulator. K/PPy/CNT composite has been deposited as sensing membrane on the top of ZrO₂ layer; 1 μl of cholesterol oxidase (ChOx) has been immobilized on K/PPy/CNT membrane via physical adsorption technique. The response of K/PPy/CNT/FET has been studied using Agilent 3458A digital multimeter in presence of phosphate buffer saline (PBS) of 50 mM, pH 7.0 and 0.9 % NaCl contained in a glass pot. During measurement, 20 μl cholesterol solutions (0.5 to 25 mM) were poured into the pot through micropipette each time. It has been found that K/PPy/CNT/FET has linearly varied from 0.5 to 20 mM. The sensitivity of this FET has been found to be ~400 μA/mM/mm² with regression coefficient (r) ~ 0.998. The proposed ENFET has response time of 1 s and stability up to 6 months. The experiment has been repeated 10 times, and only 2.0 % output variation has been observed. The limit of detection (LoD) and Michaelis-Menten constant (K ₘ) were found to be ~1.4 and 2.5 mM, respectively. The results obtained in this work show negligible interference (3.7 %) with uric acid, glucose and urea.