Biosensors and Their Applications

Study Notes

A biosensor is an analytical device that converts a biological response into an electrical signal, proportional to the concentration of an analyte in the reaction.
It consists of a biological receptor (e.g. tissue, microorganism, organelle, cell receptor, enzyme, antibody, or nucleic acid) and a transducer.
The biological receptor interacts with the target analyte, and the transducer converts the biochemical signal into a measurable and quantifiable signal.

The transducer is responsible for converting the biochemical signal into a measurable signal.
The output signal can be piezo-electrical, optical, electrochemical, etc.
Examples of transducers include pH sensors, electrochemical sensors, and piezoelectric sensors.

Selectivity: ability to selectively bind and respond only to the desired analyte.
Sensitivity: ability to generate a signal in response to small fluctuations in the concentration of the target analyte.
Stability: ability to resist change in its performance over a period of time in response to external factors.
Reproducibility: ability to produce reliable data.
Detection limit: lowest concentration of the target analyte that can elicit a measurable signal.
Response time: time taken by the biosensor to generate a signal or response following the interaction of the biological receptor with the target analyte.

Electrochemical biosensors: suitable for detecting hybridized DNA, DNA binding drugs, and glucose concentration.
Potentiometric biosensors: measure changes in pH and ion concentrations resulting from antigen/antibody interactions.
Conductometric biosensors: measure the electrical conductivity of the solution during a biochemical reaction.
Amperometric-based biosensors: detect changes in current potentials during redox reactions when antigen/antibody pairing occurs.
Mass-based biosensors: use piezoelectric biosensors, such as quartz crystal microbalance (QCM), to produce an electrical signal when a mechanical force is applied.

Disease monitoring
Drug discovery
Detection of pollutants, disease-causing microorganisms, and markers in bodily fluids (blood, urine, saliva, sweat)

Analyte: a substance of interest that needs detection.
Bioreceptor: a molecule that specifically recognizes the analyte.
Bio-recognition: the process of signal generation upon interaction of the bioreceptor with the analyte.
Transducer: an element that converts one form of energy into another.