Modeling and simulation of a biosensor
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I. Motivation
Biosensors have recently become a topic of major scientific interest with a wide variety of potential applications. They currently are used to identify herbicide or bacterial contamination in food or to measure blood glucose levels in diabetics. A new field of intense research is identification of disease related mutations in human genes, for example it is now possible to screen more than 75,000 different DNA sequences on a single DNA sensor array. Continued improvements in sensitivity and ease of use as well as the development of new biosensors customized for novel applications are important aims in this field of research.
Biosensors take advantage of the high selectivity and sensitivity of molecular recognition by biological macromolecules. Examples of such biological recognition elements (sensing units) are antibodies, nucleic acids, enzymes and entire receptors. The sensing unit of a biosensor is intimately coupled with a chemical or physical transducer. This transducer unit converts the result of the recognition event into a signal that can be measured. There are three main classes of transducers based on different detection principles: 1. optical sensors such as fibre optics or evanescent wave devices, 2. electrochemical devices which measure changes in conductivity or capacitance, often enhanced by redox indicators, 3. mass-sensitive devices such as quartz crystal microbalances.
Following the research concept of caesar, an interdisciplinary research team with expertise in physics, engineering, mathematics, chemistry and molecular biology is developing a biosensor system that uses highly selective nucleic acids, so-called aptamers, as the sensing unit. Aptamers specifically bind biologically relevant molecules such as proteins, metabolites or hormones. The binding of the aptamer to its cognate ligand results in an increase in mass which is detected by a mass-sensitive transducer, a quartz crystal microbalance, more specifically a surface acoustic wave (SAW) sensor. The design and characterization of a microbalance with improved properties is supported by mathematical models, which are developed in the Modeling and Simulation Group.
