Biosensors and Bioelectronics Lecture Notes

An analytical device containing immobilized biological material (enzyme, antibody, nucleic acid, hormone, organelle, or whole cell).
This material interacts specifically with an analyte.
The interaction produces physical, chemical, or electrical signals that can be measured.
An analyte is a compound (e.g., glucose, urea, drug, pesticide) whose concentration needs measurement.

Sensitive biological element.
Examples: tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids.

Analyte: The substance being measured.
Bioreceptor: Interacts with the analyte (examples: Enzyme, Antibody, Microorganism).
Transducer: Converts the interaction into a measurable signal.
- Examples: Electrode, Semiconductor, pH Electrode, Thermistor, Photon Counter, Piezoelectric Device.
Measurable Signal: Electric Signal.

Based on the principle of signal transduction.
The bioreceptor interacts with a specific analyte.
The transducer measures the interaction and outputs a signal.
The intensity of the signal is proportional to the concentration of the analyte.
The signal is then amplified and processed by the electronic system.

Specificity and Sensitivity: Should be highly specific for the analyte and exhibit high sensitivity.
Manageable Factors: The reaction should be independent of manageable factors like pH, temperature, stirring, etc.
Linear Response: The response should be linear over a useful range of analyte concentrations.
Size and Biocompatibility: The device should be tiny and biocompatible.
Usability and Cost: The device should be cheap, small, easy to use, and capable of repeated use.

Used to bind to the target molecule.
Must be highly specific, stable under storage conditions, and able to be immobilized.
Main function is to interact specifically with the target compound.
The ability of the bioelement to interact specifically is the basis for biosensors.

The signal from the transducer is passed to the microprocessor where it is amplified and analyzed.
Data is then converted to concentration units and transferred to the display unit.

Used for the detection of pathogens in food.
The presence of E. coli in vegetables is a bioindicator of fecal contamination in food.
E. coli has been measured by detecting variation in pH caused by ammonia (produced by urease–E. coli antibody conjugate) using potentiometric alternating biosensing systems.
Enzymatic biosensors are also employed in the dairy industry.

Glucose biosensors are widely used in clinical applications for the diagnosis of diabetes mellitus.
A novel biosensor, based on hafnium oxide ( $HfO_2$ ), has been used for the early stage detection of human interleukin.
Also used for the detection of cardiovascular diseases.
Used to detect pregnancy.

Enzyme‐based biosensors can be applied in the pharmaceutical industry for monitoring chemical parameters in the production process (in bioreactors).
Affinity biosensors are suitable for high‐throughput screening of bioprocess‐produced antibodies and for drug screening.
Oligonucleotide‐immobilized biosensors for interactions studies between a surface-linked DNA and the target drug or for hybridization studies.

Biosensors find wide application for measurement, estimation, and control of water, air, and soil contaminants.
Determination of pesticides can be made by a potentiometric biosensor.
An amperometric basic sensor can be used for analyses of water pollution from herbicide.
The concentration of ammonia can be defined with a microbe biosensor with cells of type Nitrosomonas sp.