Abstract
Histamine release from rat basophilic leukemia (RBL-2H3) cells was continuously measured using a histamine oxidase (HO)-immobilized on-line electrochemical sensor. The sensor has a carbon-based electrode modified with a bilayer of osmium-polyvinylpyrridine-based gel containing horseradish peroxidase (HRP) and BSA containing HO. The high specificity of the enzyme made the sensor highly selective with regards to diamines such as putrescine and cadaverine. We obtained a low detection limit of 23 nM owing to the low operation potential of the sensor (below 0 V vs. Ag/AgCl) and the high activity of the enzyme after immobilization. Moreover, the sensor had a high conversion efficiency. The sensor response was unaffected by 400 min of continuous histamine measurement and by more than 2 weeks of storage in a refrigerator. We combined the histamine sensor with a microdialysis (MD) sampling probe and used it to measure the histamine concentration of RBL-2H3 cells stimulated with dinitrophenylated bovine serum albumin (DNP-BSA) after incubation with IgE. We also fabricated a small volume histamine sensor by the microfabrication technique and were able to measure the histamine release from a small mast cell colony in real time with the sensor by drawing the extracellular solution continuously through a sampling capillary located near the cells.
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