Question

List two advantages and disadvantages of calorimetric biosensor

Answer 1

Many enzyme catalysed reactions are exothermic, generating heat (Table 6.1) which may be used as a basis for measuring the rate of reaction and, hence, the analyte concentration. This represents the most generally applicable type of biosensor. The temperature changes are usually determined by means of thermistors at the entrance and exit of small packed bed columns containing immobilised enzymes within a constant temperature environment (Figure 6.2). Under such closely controlled conditions, up to 80% of the heat generated in the reaction may be registered as a temperature change in the sample stream. This may be simply calculated from the enthalpy change and the amount reacted. If a 1 mM reactant is completely converted to product in a reaction generating 100 kJ ˣ mol-1 then each ml of solution generates 0.1 J of heat. At 80% efficiency, this will cause a change in temperature of the solution amounting to approximately 0.02�C. This is about the temperature change commonly encountered and necessitates a temperature resolution of 0.0001�C for the biosensor to be generally useful.