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Biosensors tend to be defined as devices which are capable of detecting the presence or absence of specific analytes/targets, and which utilise biological components [REF]. Our project focuses specifically on biosensors which use genetic circuits to convert the presence or absence of a target molecule/condition into a reporter.
A target molecule or condition can be detected in many different ways. Two commonly used mechanisms are transcription factor binding, where the target molecule either activates or represses a TF to regulate expression from a promoter, and riboswitches where a target molecule can repress or activate translation of a gene [REFs]. This 'detection' part of biosensors can be derived either de novo, or from natural sensing mechanisms which are found ubiquitously in organisms. For example, the PhoPQ two-component system in Pseudomonas aerugionsa is able to detect many inputs, such as low pH and high magnesium ion concentrations [REF]. Therefore, this native sensing mechanism could be used as a starting point for the development of biosensors.
The reporter has a variety of forms, from fluorescence proteins to enzymes to effectors. Typically, the reporter will be something that is easily visualised without specialised equipment (e.g. chromoproteins or fluorescent proteins which can be seen with the naked eye), or an output which can be recognised by an electronic device and quantified (e.g. a change in pH).
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![]() Biosensor image
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