Continuous measurement of histamine from rat basophilic leukemia cells (RBL-2H3) with an on-line sensor using histamine oxidase

Histamine release from rat basophilic leukemia (RBL-2H3) cells was continuo usly measured using a histamine oxidase (HO)-immobilized on-line electroche mical sensor. The sensor has a carbon-based electrode modified with a bilay er of osmium-polyvinylpynidine-based gel containing horseradish peroxidase (HRP) and BSA containing HO. The high specificity of the enzyme made the se nsor highly selective with regards to diamines such as putrescine and cadav erine. We obtained a low detection limit of 23 nM owing to the low operatio n 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 hi stamine measurement and by more than 2 weeks of storage in a refrigerator. We combined the histamine sensor with a microdialysis (MD) sampling probe a nd used it to measure the histamine concentration of RBL-2H3 cells stimulat ed with dinitrophenylated bovine serum albumin (DNP-BSA) after incubation w ith IgE. We also fabricated a small volume histamine sensor by the microfab rication technique and were able to measure the histamine release from a sm all mast cell colony in real time with the sensor by drawing the extracellu lar solution continuously through a sampling capillary located near the cel ls. (C) 2000 Elsevier Science S.A. All rights reserved.