THERMAL BIOSENSORS
Nour TAHA / Jannis HOLTKÖTTER
History
History
Extent of reaction
Structural Dynamics of dissolved biomolecules
Definition
- Thermal Biosensors reflect the changes in the temperature within the biological reactions medium.
- It refers to measuring the changes in the temperature of the circulating fluid following the reaction of a suitable substrate with the immobilized enzyme molecules.
- The devices used are usually referred to as enzyme thermistors.
Definition
Concept
Schematic of an enzyme thermistor
Principles of measurement
Thermometric measurement corresponds to the measurement of heat evolved or absorbed during a biochemical reaction. It’s important to note that the total heat evolution or absorption is proportional to 2 main parameters:
Total number of molecules created in the biochemical reaction
The change in temperature is also proportional to the enthalpy change and inversely proportional to the heat capacity of the system.
Heat capacity of the system
Change in the temperature
Conventional Thermal Biosensor
The first design ever in the 1970s contained immobilized enzyme columns.
- Water bath contained devices that were thermostated placed by a temperature controlled metal block containing an enzyme column.
- Peristatic pump maintained the flow of the buffer
- Two-channel instrument is used to split equally the flow of the buffer and sample into the sample and reference probes.
- Reference probe has a non-enzyme protein cross-linked with glutaraldehyde and is normally subtracted from the signal of the enzyme column to give us the final result.
- Amplifier is connected to a strip chart recorder for monitoring the response as a thermometric peak.
Updated versions
- Mini thermometric systems: used micro-machining, liquid filters, transducers, microvalves and micropumps. Two types were developed, plastic chip sensor and micro column sensor.
- Micro thermometric systems: two types also were developed: thermopile based and thermistor based micro-biosensor.
- Multisensing thermometric system: had a single micro-column with serially portioned detection regions. Each region contains a specific enzyme corresponding to a measurement of a specific analyst followed by a sensitive thermistor. The responses generated from different thermistors and channels provides an integrated picture of the concentration of the various analytes in the injected sample.
Determination of Metabolites
Example: MicroCal™iTC200System
Determination of Metabolites
Blood Analysis
Blood Analysis
Environmental Control
Environmental Control
On-Line Monitoring of Bioprocesses
On-line Monitoring of Bioprocesses
Biosensors
of
Cellular Stress
Measurements in Organic Solvents
Measurements in Organic Solvents
Benefits
High specificity
Thermal Isolation
Fast Response time
Allows batch fabrication
Reduced Power Consumption
Rapid and Continous measurement
Improved Sensitivity and Linear Range
Reduced Thermal Mass and Sample Volume
Integration of miniaturized devices at low cost
Benefits
Challenges
- Biological molecules possess special structures and functions.
- The processing, characterization, interface problems, availability of high quality nanomaterials, tailoring of nanomaterials, and the mechanisms governing the behaviour of these nanoscale composites on the surface of electrodes .
Challenges
Microscale Technology
Microscale Technology
Hybrid Biosensors
A dual-signal hybrid biosensor for simultaneous thermal and electrical determination of tyrosinase-catalyzed reaction.
Hybrid biosensor principle: a combination of two sensing principles of thermal and electrochemical measurement.
A schematic diagram of a ferrocene-mediated hybrid glucose biosensor