title: Highly sensitive potassium-doped polypyrrole/carbon nanotube-based enzyme field effect transistor (ENFET) for cholesterol detection.
abstract: 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/mm(2) 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.
authors.affiliation: Department of Electronics and Communication Engineering, Tezpur University, Tezpur, Assam, 784028, India, abdulnpl@gmail.com.
authors.forename: Md Abdul
authors.initials: MA
authors.lastname: Barik
authors.forename: Manoj Kumar
authors.initials: MK
authors.lastname: Sarma
authors.forename: C R
authors.initials: CR
authors.lastname: Sarkar
authors.forename: Jiten Ch
authors.initials: JCh
authors.lastname: Dutta
mesh_terms: D015374:Biosensing Techniques; D002784:Cholesterol / Q000737:chemistry / Q000302:isolation & purification*; D004566:Electrodes; D004800:Enzymes, Immobilized; D006801:Humans; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D011108:Polymers; D011758:Pyrroles; D017971:Tin Compounds; C067635:polypyrrole; C109984:indium tin oxide; D002784:Cholesterol; D015040:Zirconium; D011188:Potassium; C028541:zirconium oxide