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THERMAL BIOSENSORS

CONCLUSION

APPLICATIONS

TECHNOLOGY

INTRODUCTION

Nour TAHA / Jannis HOLTKÖTTER

Introduction

History

Calorimetry

Biosensors

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:

Molar enthalpy

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.

Total heat

Moles of product

Molar enthalpy change

Heat capacity of the system

Change in the temperature

Instrumentation

Wheatstone Bridge

Immobilization Matrix

Injection valve

Plastic Column

Thermistor

Peristaltic pump

Heat Exchanger

Thermopile

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.

Applications

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

Hardware

Control Algorithms

On-line Monitoring of Bioprocesses

Biosensors

of

Cellular Stress

Corrective Action

Measurements in Organic Solvents

Measurements in Organic Solvents

Conclusion

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

Future Prospects

Future

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

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