Molecular Fluorescence Excitation–Emission Matrices Relevant to Tissue Spectroscopy¶

Abstract

In vivo and ex vivo studies of fluorescence from endogenous and exogenous molecules in tissues and cells are common for applications such as detection or characterization of early disease. A systematic determination of the excitation-emission matrices (EEM) of known and putative endogenous fluorophores and a number of exogenous fluorescent photodynamic therapy drugs has been performed in solution. The excitation wavelength range was 250-520 nm, with fluorescence emission spectra collected in the range 260-750 nm. In addition, EEM of intact normal and adenomatous human colon tissues are presented as an example of the relationship to the EEM of constituent fluorophores and illustrating the effects of tissue chromophore absorption. As a means to make this large quantity of spectral data generally available, an interactive database has been developed. This currently includes EEM and also absorption spectra of 35 different endogenous and exogenous fluorophores and chromophores and six photosensitizing agents. It is intended to maintain and extend this database in the public domain, accessible through the Photochemistry and Photobiology website (http://www.aspjournal. com/).

Identification of skin lesions through aminolaevulinic acid-mediated photodynamic detection

“…Others skin components such as flavins do not have a great contribution due to the excitation wavelength, which is not within the absorption wavelengths of these components [26].…”

A handheld fluorescence molecular tomography system for intraoperative optical imaging of tumor margins

“…[3][4][5][6] Optical-based imaging technologies appear to be ideal for intraoperative imaging as they can be miniaturized, and are inexpensive, fast, and sensitive. 7 While to date most of the optical studies conducted focused on the intrinsic fluorescence of malignant tissues, [8][9][10][11][12][13][14] the high heterogeneity of malignant and benign tissues in their molecular and cellular compositions often leads to unacceptable false-positive rates for benign tissues and unacceptable false-negative rates for malignant tissues using these autofluorescence and intrinsic measurements. 15 A large number of studies using nontargeted exogenous fluorescent markers (e.g., indocyanine green (ICG) and ALA-induced PpIX) have shown improved tumor detection.…”

Rapid near-infrared fluorescence excitation–emission matrix spectroscopy for multifluorophore characterization using an acousto-optic tunable filter technique

“…4,5 In typical existing EEM systems, four different types of tunable excitation light modules are usually used: ͑1͒ an arc lamp coupled with a monochromator or interference bandpass filters, ͑2͒ an arc lamp coupled with double monochromators, ͑3͒ a nitrogen-pumped dye laser, and/or ͑4͒ an optical parametric oscillator ͑OPO͒ tunable laser. [3][4][5][6][7][8] But all these types of tunable light sources use stepper motor-type mechanisms for rotating gratings or filter wheels or crystals for tuning the excitation light wavelengths. This mechanical movement imposes limitations on the speed of tunings from one wavelength to another, resulting in lengthy EEM data acquisitions ͑up to minutes or hours͒ which are unsuitable for in vivo biomedical applications.…”

“…This mechanical movement imposes limitations on the speed of tunings from one wavelength to another, resulting in lengthy EEM data acquisitions ͑up to minutes or hours͒ which are unsuitable for in vivo biomedical applications. [4][5][6][7][8] To tackle this problem, an acousto-optic tunable filter ͑AOTF͒ can be employed to electronically tune various wavelengths of a xenon arc lamp with a high-throughput ͑Ͼ90% diffraction efficiency͒ within milliseconds without moving parts by varying the radio frequency ͑RF͒ of the acoustic wave propagating through the crystal. 9 To date, most EEM studies have focused on excitation wavelengths ranging between ultraviolet ͑UV͒ and shorter wavelength visible ͑VIS͒ light.…”

“…9 To date, most EEM studies have focused on excitation wavelengths ranging between ultraviolet ͑UV͒ and shorter wavelength visible ͑VIS͒ light. [4][5][6][7] Near-infrared ͑NIR͒ fluorescence EEM, which has the potential of providing the optimized excitation-emission wavelengths maxima for realizing deep-tissue imaging, has not yet been reported in the literature. In this work, we report on a novel AOTF-based NIR fluorescence excitation-emission matrix ͑EEM͒ spectroscopy technique for rapid multifluorophore analysis and characterization.…”