SURFACE MODIFIED SENSORS FOR THE DETERMINATION OF BIOMOLECULES/DRUGS

Abstract

Electrochemistry is a field of science, which deals with the interrelation of electrical and chemical processes. The electrochemical studies can encompass the electricity production from the released energy by the spontaneous chemical reactions and the applicability of electrical energy to accomplish non-spontaneous chemical transformations. The potent applications of electrochemistry in day to day life comprises energy conservation and storage devices, pollution control, biomedical research, corrosion, electrophoresis, fuel cells, electroplating etc. [1-5]. Electrochemistry also comprises further applications in the determination of mechanism of the electrode reactions as well as redox properties of biomolecules/drugs, which can also furnish insights on their metabolic products and pharmaceutical activities [6]. Firstly, in the year 1791, Luigi Galvani examined the impact of atmospheric electric discharge on a frog’s leg, which was considered as the foundation experiment of electrochemistry. Further research in this area was started by Michael Faraday in 1832 and new electrochemical terminology was introduced by him, such as, cathode, anode, electrode, cation, anion and two fundamental laws of electrolysis. In the year 1888, Walther Hermann Nernst drawn out a theory relating the electromotive force to the energy of a chemical reaction in an electrochemical cell and derived an important equation known as ―Nernst Equation‖. In 1923, ―Father of electroanalytical chemistry‖, Czech scientist Jaroslav Heyrovsky, discovered the polarographic method of analysis, where current was measured as a function of the applied electrode potential and received Nobel Prize in 1959. This discovery of polarography resulted in the development of advanced electroanalytical methods, modern instruments, processors of analytical data and evolution of biosensors used in the electrochemical analysis of biomolecules [7,8]. The electrochemical methods are facile approach in direct analysis of analytes in pharmaceutical formulations and physiological fluids due to the capability of fast determining the drug content in blood, serum, plasma and urine samples without involving any pre-separation steps with good accuracy and selectivity. Electrochemical methods provide countless advantages such as rapid analysis, high accuracy, good sensitivity and selectivity, eco-friendly, long term stability and reproducibility, no requirement of pre-analysis steps and expensive instruments and hence, electrochemical analysis is considered as Green chemistry. Electrochemical techniques usually employ a three electrode system, which contains a reference electrode, a counter or auxiliary electrode and a working electrode. The oxidation and reduction processes take place at the surface of working electrode, which significantly controls the sensitivity therefore; improvement of surface morphology