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1 February 1993 Measurement of in vivo tumorous/normal tissue pH by localized spectroscopy using a fluorescent marker
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The fluorescein derivatives are now commonly used for measuring intracellular pH. Cytoplasmic pH is estimated from the shape of the pH-dependent excitation spectrum of the trapped fluorescent marker. The ability of 2',7'-bis-(2 carboxyethyl)-5-(and-6)-carboxyfluorescein as a fluorescent probe for pH monitoring in vivo is evaluated and the in vitro pH sensitivity ofthis fluorescent probe is investigated. In vivo experiments were carried out on tumor-grafted mice. Dyes were injected intraperitoneally and fluorescence emission spectra were collected at different excitation wavelengths by an adapted system bearing optic fibers. Ratios were calculated on the basis of maximum emission wavelength fluorescence intensities at retained excitation wavelengths. The choice of wavelength excitation was restricted to 465 nm because the 450-nm excitation wavelength leads to problems of autofluorescence and tissue penetration of light. At a 500/465 ratio, the pH sensitivity is greatly reduced. Kinetic profiles of fluorescence intensities show low tissue and tumoral uptake with a plateau phase 100 mm after dye injection. Ratio values reach a steady state 30 mm after dye injection and remain stable during the whole experiment. The results clearly indicate differences in ratio values for tumoral and normal tissues (p < 0.005). The tumoral ratio (1.88 ± 0.07) is always lower than normal tissue ratio (2.45 ± 0.09).
Jean-Marie Devoisselle, Vincent Maunoury, Serge R. Mordon, and Denise Coustaut "Measurement of in vivo tumorous/normal tissue pH by localized spectroscopy using a fluorescent marker," Optical Engineering 32(2), (1 February 1993).
Published: 1 February 1993

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