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Anti‐Stokes fluorescence from endogenously formed protoporphyrin IX – Implications for clinical multiphoton diagnostics
Author(s) -
Kantere Despina,
Guldbrand Stina,
Paoli John,
Goksör Mattias,
Hanstorp Dag,
Wennberg AnnMarie,
Smedh Maria,
Ericson Marica B.
Publication year - 2013
Publication title -
journal of biophotonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 66
eISSN - 1864-0648
pISSN - 1864-063X
DOI - 10.1002/jbio.201200119
Subject(s) - protoporphyrin ix , autofluorescence , two photon excitation microscopy , fluorescence , photodynamic therapy , excitation wavelength , chemistry , fluorescence lifetime imaging microscopy , contrast (vision) , multiphoton fluorescence microscope , fluorescence microscope , biophysics , pathology , optics , medicine , biology , physics , organic chemistry
Multiphoton imaging based on two‐photon excitation is making its way into the clinics, particularly for skin cancer diagnostics. It has been suggested that endogenously formed protoporphyrin IX (PpIX) induced by aminolevulinic acid or methylaminolevulinate can be applied to improve tumor contrast, in connection to imaging of tissue autofluorescence. However, previous reports are limited to cell studies and data from tissue are scarce. No report shows conclusive evidence that endogenously formed PpIX increases tumor contrast when performing multiphoton imaging in the clinical situation. We here demonstrate by spectral analysis that two‐photon excitation of endogenously formed PpIX does not provide additional contrast in superficial basal cell carcinomas. In fact, the PpIX signal is overshadowed by the autofluorescent background. The results show that PpIX should be excited at a wavelength giving rise to one‐photon anti‐Stokes fluorescence, to overcome the autofluorescent background. Thus, this study reports on a plausible method, which can be implemented for clinical investigations on endogenously formed PpIX using multiphoton microscopy (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)