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Introduction to Biosensors
One of the possible applications of our project is to be used as a biosensor. A general definition of a biosensor is that it is a device which uses a biological recognition element to detect some specific analyte, and then transduce this detection event to give a quantitative output signal. The recognition element could be an enzyme, an antibody or in our case a whole cell or better a colony of cells. The output in our case would be measured as an electrical potential and will be a stream of electrons.
Whole cell biosensors
Using whole cells as biosensor elements has some potential advantages:
· They are ‘self-manufacturing’
· They need to be merely grown and harvested to be ready for use
· They are potentially cheaper and easier to manufacture
· They detect only analytes that are available to interact with living organisms; bioavailable analytes
Sensitivity and Dynamic range
Some values that characterise a biosensor are the sensitivity and the dynamic range.
· Sensitivity is the lowest analyte concentration to which a detectable response is observed.
· Dynamic range is the range of analyte concentrations over which analyte concentration can be estimated based on the response.
Storage and Distribution
There are some issues considering the storage and distribution of living cells biosensors since for the biosensor to be active the cells have to be alive. One way that is commonly used to preserve the cells alive is freeze-drying for long periods. Another solution is to use microorganisms that form spores which can survive for long time and under various conditions.
Using whole cell biosensors to the Field - Regulatory Issues
There are a lot of problems in actually being able to use a biosensor in the field since the regulations are strict and yet no biosensor has taken such an approval. Thus, there are several different types of biosensors designed:
· Biosensors to be used in a laboratory
· Biosensors to be used in a contained device, but outside laboratory
· Biosensors to be exposed directly to the environment but not to survive longer than required for reporting the specific analyte levels
· Biosensors to survive and stay in the field for long periods
So far the only biosensors that have gotten approval to be used are of the first type and there are some hopes for the second type to be allowed. A for the rest it might take a long time till it is decided if they can be safely used.
References
Synthetic Biology and the art of biosensor design, French et al.
Development of biosensors for the detection of arsenic in drinking water, French et al.
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