Development of an on-line sensing system of catecholamines and its application for medical use

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An electrochemical sensor system was developed which allows real-time measurement and feedback of catecholamine concentrations, and which can be used in the control of artificial hearts.Electrochemical analyzes were carried out using a carbon fiber working electrode, an Ag-AgCl reference electrode, and a potentiostat. The operating parameters of the pneumatically-driven artificial heart system were altered in accordance with the algorithm for changes in the catecholamine concentration.The minimum detectable concentrations of both adrenaline and noradrenaline in a mock circulatory system using a phosphate-buffered solution were approximately 1-2 ng/ml (10^<-8> mol/l). An artificial heart control system utilizing this arrangement performed satisfactorily without delay although the sensitivity of the sensor decreased when placed in goat plasma instead of phosphate-buffered solution, due to the adsorption on to the electrodes of various substances such as plasma proteins.A microdialysis te … More chnique was therefore used in order to prevent blood proteins from being adsorbed on to the electrods. The dialytic solution was flushed through a cellulose microtube (cut-off molecular weight=50000) for dialysis ; the microtube was immersed in the goat plasma, and the catecholamine concentrations in the dialytic solution were measured using the above electrochemical detector. With this system, the ratio between catecholamine concentrations in the dialytic solution and that in the plasma was approximately 20% when the flow rate of the dialytic solution was 10 ml/min, with a time delay of approximately 90 seconds. Using this system, the minimum detectable concentration of both plasma adrenaline and noradrenaline was 10^<-7> mol/l ; it was possible to alter the driving conditions in accordance with the algorithm for changes in the catecholamine concentration of the plasma. The authors are currently attempting to : 1)incorporate the electrodes and the dialytic system into one microsensor system, and 2)improve the sensitivity of the sensor to 10^<-9> mol/l. Less