A Microdialysis Probe Coupled with A Miniaturized Thermal Glucose Sensor for In Vivo Monitoring

Thermal Biosensor and Microbiosensor Techniques

This chapter describes principles and features of thermal biosensors and microbiosensors and includes a discussion of different thermal transducers. A number of instrumental concepts are described in detail from larger flow injection instruments to miniaturized devices and chip designs with thermal arrays. A thermal–electrochemical hybrid sensor is also presented. The chapter contains many descriptions of actual assays from different fields, such as process and in vivo monitoring, multianalyte determination, operation in organic solvents, and environmental analysis.

Principles and applications of thermal biosensors

A review of thermistor-based calorimetric measurement is presented. The principles of thermometric measurements are highlighted in the introduction followed by the instrumentation, materials and methods. Various applications relating to enzyme activity measurements, clinical monitoring, process monitoring, multianalyte determination, hybrid sensing, environmental monitoring, non-aqueous measurements and other miscellaneous applications are described. A brief note on future developments and a detailed reference list is also included.

Principles of enzyme thermistor systems: applications to biomedical and other measurements

This chapter presents an overview of thermistor-based calorimetric measurements. Bioanalytical applications are emphasized from both the chemical and biomedical points of view. The introductory section elucidates the principles involved in the thermometric measurements. The following section describes in detail the evolution of the various versions of enzyme-thermistor devices. Special emphasis is laid on the description of modern "mini" and "miniaturized" versions of enzyme thermistors. Hybrid devices are also introduced in this section. In the sections on applications, the clinical/biomedical areas are dealt with separately, followed by other applications. Mention is also made of miscellaneous applications. A special section is devoted to future developments, wherein novel concepts of telemedicine and home diagnostics are highlighted. The role of communication and information technology in telemedicine is also mentioned. In the concluding sections, an attempt is made to incorporate the most recent references on specific topics based on enzyme-thermistor systems.

A flow injection microdialysis sampling chemiluminescence system for in vivo on-line monitoring of glucose in intravenous and subcutaneous tissue fluid microdialysates

A novel flow injection on-line microdialysis system for in vivo monitoring of glucose in subcutaneous tissue fluid and blood is described. An implantable loop-type microdialysis probe was used for subcutaneous sampling, and a flow-through microdialyzer was used for intravenous sampling by pumping of the blood from the tested rabbit through the microdialyzer located outside the living system at a flow rate of 10 microL/min. The perfusion rate of the dialysate was 20 microL/min. The glucose in the dialysate was detected on-line with a flow injection chemiluminescence system after passing through an immobilized glucose oxidase reactor. The calibration of the detector system (including reactor) and monitoring of baseline drifts were performed simultaneously to improve the reliability of the monitoring process. The dialysate sample volume was 20 microL, and the sample throughout was 28 h-1. The variation of glucose level in subcutaneous tissue fluid and blood of the rabbits was monitored after the administration of glucose or insulin to demonstrate the favorable resolution and reliability of the system for in vivo on-line monitoring.

Thermistor-based biosensing

In this review a universal thermistor-based biosensor system is described with examples from clinical chemistry, bioprocess monitoring and environmental control. The technique is based on the measurement of the small temperature changes associated with enzymatic reactions occurring in a microreactor with immobilized enzyme. The system has good operational stability and a sensitivity that permits measurements down to 1 microM concentrations. Current developments include devices constructed by micromachining for multisensing purposes and miniaturised instrumentation intended for use in portable monitoring. With use of special supports for enzyme immobilisation even untreated whole blood samples can be applied. Another current line of investigation involves hybrid biosensors, such as combinations of electrochemistry and calorimetry into bioelectrocalorimetric devices with interesting new properties.