Evaluation of Different Functionalized CNTs for Development of Choline Amperometric Biosensor

Choline oxidase (ChOx) was chosen as a model enzyme for evaluating the performance of CNTs’ functional groups for development of enzyme electrodes. CNTs were functionalized with carboxylic acid, amine or amide groups. Carboxylic acid, amine and amide functionalized CNTs were obtained by acid treatment, ethylenediamine or tetraethylenepentamine chemically modification and ammonia plasma treatment, respectively. The CNTs with different functional groups were mixed with 1-butyl-3-methylimidazolium tetrafluoroborate as a typical room temperature ionic liquid. ChOx was adsorbed on the thus prepared nanocomposites containing different modified electrodes and its electron transfer and electroanalytical response towards choline was investigated. The resulting data showed that the ammonia plasma treated nanocomposite had higher apparent heterogeneous electron transfer rate constant (2.74 s-1) than the others, indicating more facile and rapid rates of electron transfer; while, nanocomposites modified with tetraethylenepentamine functionalized CNTs showed the most sensitive response towards choline (1.09 × 103 A M-1 m-2) with the lowest detection limit of 5.81 × 10-6 M. Consequently, tetraethylenepentamine modified electrodes were more convenient for choline biosensing applications.