Fiber-based time-resolved fluorescence and phosphorescence spectroscopy of tumors

The study of metabolic and oxygen states of cells in a tumor in vivo is crucial for understanding of the mechanisms responsible for the tumor development and provides background for the relevant tumor’s treatment. Here, we show that a specially designed implantable fiber-optical probe provides a promising tool for optical interrogation of metabolic and oxygen states of a tumor in vivo. In our experiments, the excitation light from a ps diode laser source is delivered to the sample through an exchangeable tip via a multimode fiber, and the emission light is transferred to the detector by another multimode fiber. Fluorescence lifetime of nicotinamid adenine dinucleotide (NAD(P)H) and phosphorescence lifetime of an oxygen sensor based on iridium (III) complex of enzothienylpyridine (BTPDM1) are explored both in model experiment in solutions, and in living mice. The luminescence spectroscopy data is substantiated with immunohistochemistry experiments. To the best of our knowledge, the measurements of both metabolic status and oxygenation of tumor in vivo by fluorescence/phosphorescence lifetime spectroscopy with a fiber-optic probe are done for the first time.