Biosensors and biochips-advances in biological and medical diagnostics

In the past two decades, the biological and medical fields have seen great advances in the development of biosensors and biochips capable of characterizing and quantifying biomolecules. This review is meant to provide an overview of the various types of biosensors and biochips that have been developed for biological and medical applications, along with significant advances over the last several years in these technologies. It also attempts to describe various classification schemes that can be used for categorizing the different biosensors and provide relevant examples of these classification schemes from recent literature.

Humankind has been performing bioanalysis since the dawn of time, using the sensory nerve cells of the nose to detect scents or the enzymatic reactions in the tongue to taste food. As time has progressed, so has our level of understanding about the function of living organisms in detecting trace amounts of biochemicals in complex systems. Because biological organisms are some of the most efficient machines ever created, scientists have sought to apply and copy their efficiency for use in man made creations. In particular, the recognition abilities of biological organisms for foreign substances is unparalleled. Using bioreceptors from biological organisms or receptors that have been patterned after biological systems, scientists have developed a new means of chemical analysis that often has the high selectivity of biological recognition systems. These biorecognition elements in combination with various transduction methods have helped to create the rapidly expanding fields of bioanalysis and related technologies known as biosensors and biochips. A biosensor can be generally defined as a device that consists of a biological recognition system, often called a bioreceptor, and a transducer. The interaction of the analyte with the bioreceptor is designed to produce an effect measured by the transducer, which converts the information into a measurable effect, such as an electrical signal. Figure 1 illustrates the conceptual principle of the biosensing process. Biosensors that include transducers based on integrated circuit microchips are often referred to as biochips. In general, a biochip consists of an array of individual biosensors that can be individually monitored and generally are used for the analysis of multiple analytes. Biosensors and biochips can be classified either by their bioreceptor or their transducer type (see Fig. 2). A bioreceptor is a biological molecular species (e.g., an antibody, an enzyme, a protein, or a nucleic acid) or a living biological system (e.g., cells, tissue, or whole organisms) that utilizes a biochemical mechanism for recognition

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