In vivo application of intestinal pH measurement using 2 ',7 '-bis(carboxyethyl)5,6-carboxyfluorescein (BCECF) fluorescence imaging

Measurement of gastrointestinal intramucosal pH (pH(im)) has been recognize d as an important factor in the detection of hypoxia-induced dysfunctions. However, current pH measurement techniques are limited in terms of time and spatial resolutions. A major advance in accurate pH measurement was the de velopment of the ratiometric fluorescent indicator dye, 2',7'-bis(carboxyet hyl)-5,6-carboxyfluorescein (BCECF), This study aimed to set up and validat e a fluorescence imaging technique to measure in vivo the intramucosal pH ( pH(im)) of the intestine. The intestine was inserted into an optical chambe r placed under a microscope. Animals were injected intravenously with the p H-sensitive fluorescent dye BCECF, Fluorescence was visualized by illuminat ing the intestine alternately at 490 and 470 nm, The emitted fluorescence w as directed to an intensified camera. The ratio of emitted fluorescence at excitation wavelengths of 490 and 470 mm was measured, corrected and conver ted to pH(im) by constructing a calibration curve. The pH(im) controls were performed with a pH microelectrode and were correlated with venous blood g as sampling. Results show that pH(im) is determined with an accuracy of +/- 0.07 pH units and a response time of 1 min. In conclusion pH(im) mapping of rat intestine can be obtained by fluorescence imaging using BCECF, This te chnology could be easily adapted for endoscopic pH measurements.