Summary Of Ph.d One Page.docx

Synopsis of the Thesis “Development of Biosensors based on Enzyme immobilized Conducting Polymers” In this research work, polypyrrole nanocomposites with remarkable carbon nanomaterials have been designed and developed as a transducer with an ultimate goal of fabrication of Biosensor in medical diagnostics. Recently, nanomaterials like carbon nanotubes (CNTs) have been employed in the construction of electrochemical biosensors to improve their analytical performance. Polypyrrole/c-Multiwalled-CNT nanocomposites have been electrochemically synthesized on modified steel electrode in phosphate buffer solution (PBS) with an ultimate goal of developing a biosensor by immobilizing an enzyme on this nanocomposite. Electrochemical entrapment method has been used for immobilization of enzyme on the nanocomposites for the fabrication of PPy/c-MWCNT/LOD, lactate biosensor and PPy/c-MWCNT/Urease, urease biosensor and their biosensor analysis has been obtained in real samples for sensitive and selective detection of lactate and urea in medical diagnostics. Also the optimization conditions of biosensor, effects of pH, effect of temperature, and response time on biosensor responses have been reported. The storage and stability of the biosensor has been investigated. Experimental results demonstrated that the nanocomposites shows dramatically improved performance compared to each of the individual components. In the lactate oxidase (LOD) based biosensor; LOD catalyzes the conversion of lactate to pyruvate and hydrogen peroxide, which can be oxidized at the electrode surface, and which is detected in the form of change in the current. In the Urease based biosensor the urease catalyzes the decomposition reaction of urea. The basic principle and working of potentiostat has been used for electrochemical synthesis by using cyclic voltammetric technique. PPy, PPy/MWCNTs, PPy/MWCNTs/LOD and PPy/MWCNTs/Urease nanobiocomposites have been characterized by SEM, FTIR, RAMAN, EIS, Cyclic Voltammetry. Cyclic voltammetry study determined the redox potentials of the electrochemically deposited PPy, PPy/MWCNTs nanocomposite and PPy/MWCNTs/enzyme nanobiocomposite film. The study reveald that the redox potential have considerably been lowered due to incorporation of CNTs into PPy matrix which promotes the electrontransfer of the oxidation–reduction process. From the EIS results, it has been observed that the impedance values attained for the PPy/MWCNTs nanocomposite were lowered as compared to bare steel electrode. SEM revealed the surface morphology indicating the high porosity of PPy and entrapment of CNTs by PPy in nanocomposite needed for immobilization of enzyme. Globular structure is observed in the SEM images of PPy/MWCNTs/enzyme nanobiocomposite which confirms the incorporation of enzyme. FTIR revealed the shift of bands to lower frequencies in the nanocomposites spectra as compared with PPy suggesting that an interaction between the polymer and CNT occurs. In the FTIR spectra of PPy/c-MWCNTs/LOD nanobiocomposite the appearance of additional absorption bands represents carbonyl stretch (amide I band) and N H bending (amide II band), respectively. Additionally, a broad band is observed which is attributed to an amide bond present in enzyme. This result confirms the incorporation of enzyme. RAMAN shift indicates that the electronic structure of the PPy/MWCNTs is not perturbed as a result of being incorporated into PPy. A downshift due to the entrapment of enzyme is observed. The measurement of biosensor responses and the enzymatic studies i.e. enzyme loading is reported. The potentiodynamic responses of the enzyme electrodes were measured monitoring oxidation current of H2O2 at +0.8 V. Detection limit and sensitivity of the biosensor is obtained. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and effect of temperature were determined for both biosensors. Based on Michaelis-Menten (Km) constants, it is interpreted that both enzymes immobilized into PPy/MWCNTs nanocomposites showed the highest affinities towards their substrates. Before testing the lactate biosensors for detection of lactate and urease biosensor for detection of urea, the effects of interferents (glucose, acetic acid, citric acid, L-ascorbic acid) which might be present in biological

samples were determined. The lactate content in the human sweat was measured with the lactate biosensors and the urea content in blood sample was measured with urease biosensor.