Development of electrochemical sensors for biorecognition

Graphene was discovered in the recent past and it has excellent physical, chemical, electrical, thermal and optic properties. Graphene oxide (GO) is a nanomaterial that increases the immobilization and adsorption capacity of the surface, due to its large surface area. Within the scope of the thesis, single-use voltammetric and impedimetric sensing platforms that modified with graphene oxide and its derivatives are developed in order to detect biomolecular interaction and recognition events. In the first part of the thesis, in order to examine the drug-DNA interaction by electrochemical techniques, reduced graphene oxide modified single-use biosensor platform is developed. The interaction between anticancer drug daunorubicin and double stranded DNA is monitored via voltammetric and impedimetric techniques. In the second part of the thesis, within the context of innovative electrochemical biosensors, simple, inexpensive, rapid and selective detection of miR-34a as a biomarker associated with various types of cancers, neurodegenerative and metabolic diseases such as, Alzheimer's disease and diabetes is performed by voltammetric technique using graphene oxide modified single-use biosensor platform. In the third part of the thesis, impedimetric detection of miR-660 that is a biomarker of leukemia, lung cancer, breast cancer and multiple myeloma, is performed in a practical way by chitosan and nitrogen doped reduced graphene oxide modified single-use biosensor platform. In order to show the applicability of the designed biosensor is tested in artificial serum sample. In the forth part of the thesis, enzymatic detection of glucose in body fluids are presented. This study was a part of "dual-biomarker sensing chip" which integrating enzyme and antibody-based assays for simultaneous electrochemical measurements of glucose and insulin. The glucose is monitored by chronoamperometry technique in saliva and whole blood through reaction of glucose oxidase. Therefore, the studies are being performed in order to investigate practical, easy-to-prepare, suitable for miniaturization biosensor platforms which can be used for monitoring of drug-DNA interaction, miRNA analysis, and glucose detection in body fluids.