Synthesis and characterization of immobilizing materials for biosensing application

Abstract

The development of biosensors has come from the rapid advances in health care technology as a frequent measurement of biochemical parameters such as blood cations, gases and metabolites required for effective patient care. The need for cheap and reliable sensors for monitoring such parameters has lead to exponential increase in the research and development of biosensors. Electrochemical biosensors have emerged as the most commonly used biosensors as they have been found to overcome most of the disadvantages, which inhibit the use of other types of biosensors. They are rapid, easy to handle, simple and are of low cost. The basic fact behind this bio-interaction process is that the electrochemical species such as electrons are consumed or generated producing an electrochemical signal, which can be measured by the detector. These biosensors are usually based on potentiometry and amperometry. Urea and uric acid are the most important end product of protein degradation and purine metabolism, thus their proper balance in blood is essential for overall well being and for renal health specifically. The optimal concentration of urea in blood is an indication of proper renal functioning, its high level in blood causes urinary tract obstruction, dehyradation, shock, burns and gastrointestinal bleeding, whereas a substantial low level of urea concentration causes hepatic failure, nephrotic syndrome, cachexia. Similarly abnormal uric acid levels lead to gout, chronic renal disease, some organic acidemias, leukemia, pneumonia and Lesch–Nyhan syndrome. Hence, the detection of these analytes in body fluids is clinically important indicator. Although direct spectroscopic methods can be used for their determination, but these methods are dependent on the pre-treatment of sample and cannot be used for onsite monitoring. The primary focus of this work is to develop urea and uric acid biosensors with improved properties such as sensitivity and response time by using different substrates on indium tin-oxide (ITO) glass plates and different methods of immobilization. This study identifies the already established materials for developing different biosensor which may be used for the detection of urea and uric acid in aqueous solution. The main objective of this dissertation is to use modified electrode such as BSA/PPy, MWCNT/SiO2, APTES/BS3 and GNPs/APTES as matrix for the development of urea and uric acid biosensors. Organization of the thesis This thesis is organized into 5 chapters, Chapter 1 gives introduction to several topics that are related to this research. These include fundamentals of biosensors, immobilization techniques, materials for immobilization. Chapter 2 investigates the use of bovine serum albumin during electropolymerization of pyrrole which improves the enzyme loading. Chapter 3 shows the impact of using carbon nanotubes in a sol matrix and its use in developing urea biosensor. Chapter 4 discusses the use of another matrix based on self assembled monolayer and its modification to develop uric acid biosensor. Chapter 5 signifies the use of Au nanoparticles in self assembled monolayer. Response characteristics were studied as a function of uric acid concentration.