Electrochemical biosensors

Abstract

Being inherently sensitive, simple, fast, and inexpensive, electrochemical techniques have attracted major interests in the field of biosensors. This thesis describes the use of electrochemical techniques for sensing of thrombin, oligonucleotides, and glucose.For sensing of thrombin, thiolated ferrocenyl oligonucleotides were synthesized and immobilized on gold working electrode. Thrombin was successfully detected with linear dynamic range between 10-50 nM. Sensitivity of the electrochemical detection was enhanced by coupling ferrocene activity to glucose oxidase catalytic cycle.For sensing of oligonucleotides, alumina electrodes were modified with probe oligonucleotide and electrochemical detection was carried out in a solution of ferrocenemethanol. Signal decrease due to blocking of alumina nanochannels by complementary oligonucleotides was recorded. 1x10-18 to 1x10-12 M of oligonucleotide was detected. For sensing of glucose, glucose oxidase was immobilized on gold electrode using immunoglobulin-G as the matrix. Ferrocenemethanol was used as artificial mediator of glucose oxidase. The efficiencies of different immobilization strategies for detection of millimolar amount of glucose were studied.