Electroanalysis and Biosensors in Clinical Chemistry

Electroanalysis involves the measurement or determination of a chemical or biochemical species, using a wide range of electrochemical methods. The species being measured can either bring about a direct electrochemical response that can be detected and measured, or can be induced to bring about such a response, resulting in a process that can be detected electrochemically. In both cases an interface is required between the chemical or biochemical species being measured, and the electrochemical system performing the measurement. This interface is referred to as an “electrode”. It is the transfer of electrons or ions between the electrode and the environment being sampled which is of concern in electroanalysis. The application of electrochemistry in clinical analysis is concerned with the measurement of chemical and biochemical species present in biological fluids (primarily blood but also urine and other body fluids and tissues). It is applied in several areas of critical care where its rapidity, sensitivity, precision, and accuracy at biologically relevant concentrations make it an ideal choice over other, typically slower, biochemical techniques. Indeed, it is the speed of electrochemical analysis that principally differentiates it from other methods. It is not universally applicable to clinical chemistry, however, and has only been applied in situations where such analyses are relevant. This has principally been in the analysis of blood gases and pH and blood electrolytes. Electrochemical methods are, however, gradually being extended to the analysis of small biochemical components such as sugars, amino acids and other metabolites, with the advent of enzyme-based “biosensors”. There is also little doubt that the application of electrochemistry in clinical analysis will be further exploited by the use of such biosensor devices based on other forms of biorecognition, such as antibodies, cell ligands, membranes, tissues and whole cells. These biosensor devices are also amenable to other forms of detection such as acoustic wave and optical measurements. Together, these techniques offer a wide range of advantages over traditional analytical methodologies, and will undoubtedly have a rapidly increasing impact on many types of clinical analysis. This article focuses on the use of electrochemical techniques and electrochemical biosensors and their application in clinical chemistry.