RESUMO
A new microdialysis-based glucose-sensing system with an integrated fiber-optic hybrid sensor is presented. Design and dimensions of the cell are adapted for its coupling with commercially available microdialysis techniques, thereby providing a new system for continuous glucose monitoring. The glucose level is detected via oxygen consumption which occurs as a consequence of enzymatic reaction between immobilized glucose oxidase and glucose. The use of gas-permeable Tygon tubing ensures complete and constant air-saturation of the measuring fluid in the cell. Nevertheless, a reference oxygen optode is used to detect and to compensate response changes caused by events like bacterial growth, temperature fluctuations, or failure of the peristaltic pump. In contrast to widely used electrochemical sensors, the response of the microdialysis-based fiber-optic glucose sensor is highly selective, making this sensor approach particularly advantageous for continuous glucose monitoring of patients in intensive care units. The effects of flow rate, pH, temperature, and common interferences on the sensor response are presented and discussed in detail. The sensor is evaluated in vitro using a 3-day continuous test in glucose-spiked plasma. The ability to measure glucose in humans is demonstrated by coupling the flow-through cell and commercially available microdialysis catheter CMA60. A 24-h monitoring test using this setup is successfully applied to a healthy volunteer.
Assuntos
Tecnologia de Fibra Óptica/métodos , Glucose/análise , Enzimas Imobilizadas/química , Desenho de Equipamento , Análise de Falha de Equipamento , Tecnologia de Fibra Óptica/instrumentação , Glucose Oxidase/química , Humanos , Concentração de Íons de Hidrogênio , Monitorização Fisiológica , Fibras Ópticas , Consumo de Oxigênio , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Temperatura , Fatores de TempoRESUMO
A measurement system, consisting of an optochemical glass capillary oxygen sensor, an optoelectronic measuring unit and a microdialysis catheter (CMA 60) for the extraction of the biological fluid from the subcutaneous adipose tissue of critically ill patients is reported. The capillary sensor is based on the oxygen sensitive dye platinum (II) meso-tetra(pentafluorophenyl) porphyrin (Pt-TFPP) incorporated in a polystyrene matrix. The measuring system has been tested in vitro and in vivo. In particular in vitro long-term stability of the sensor has been investigated in different measurement media (elomel, 5% mannitol, Ringer, dialysed blood). The influence of different flow rates from 0.1 up to 7.0 microl min(-1) on the sensor response as well as the oxygen recovery rate are discussed. The presented measurement system allows the measurement of oxygen in biological fluid in the range from 0 to 300 mmHg, with a resolution better than 1 mmHg and high accuracy (better than +/-1 mmHg absolute). Finally, the suitability of the described measurement system for the continuous oxygen monitoring in subcutaneous adipose tissue has been proved in in vivo investigations performed on test animals.
