Development of microbial biosensor based on conductive polymer/multiwalled carbon nanotube and its application to paracetamol determination

In this thesis, development of a multi-walled carbon nanotube (MWCNT) -Basillus sp. - glutaraldehyde modified microbial biosensor which brings a new and original perspective to biosensor technology intended for paracetamol determination. Polianiline-MWCNT composite was formed with aniline and MWCNT on a gold electrode (Au) surface in this biosensor system. Basillus sp. was immobilized on the electrode surface by dropping after activated of carboxl groups by EDC-NHS. Microorganism was crosslinked by glutaraldehyde (GA) so that prevented of running away the microorganism from the surface of the biosensor. Paracetamol measurements were carried out at 0.5 V with amperometric method by developed biosensor system. In addition, detection of the response of the biosensor by using differential pulse (DP) and cyclic voltammetry (CV) methods and DP method was used for some immobilization studies at (0 - 0.8) V potential range. The measurements were carried out with the determination of increasing current values directly proportional with paracetamol concentration using amperometric method. In the optimization studies of the biosensor firstly bioactive layer components such as optimum aniline concentration, optimum MWCNT amount, optimum EDC-NHS proportion, optimum microorganism amount and optimum glutaraldehyde concentration were carried out. In the optimization of working conditions; optimum pH and optimum temperature were also investigated. In the characterization studies of the biosensor some paramaters such as linearity, reproducibility, storage stability, substrat specificity, interference effect and drug sample analysed were determined. From the result of the optimization studies, the optimum aniline concentration, optimum MWCNT amount, optimum EDC-NHS proportion, optimum microorganism amount and optimum glutaraldehyde concentration were determined to 0.05 M, 1 mg/mL, 1 : 1.5 M, 10 mg/mL ve 0.5 %, respectively. From the experiments the phosphate buffer (50 mM, pH 7.0) and 30˚C were chosen to be optimum working conditions for the microbial biosensor. It was determined at the characterization studies on the biosensor that linear curves were obtained between the ranges from 25 to 250 µM paracetamol concentration, detection limit and response time were reached 7.9 µM and 4.8 s, respectively. At the repeatability experiments (n=7), the average value, standard deviation, (SD) and coefficent of variation (CV %) were calculated to be 250.65 µM, ±1.55, 0.62 % for 250 µM paracetamol concentration, consecutively. Also, determination of paracetamol were carried out in drug samples by developed biosensor and a reference method.