Biophysics, Oral Report

AUTOFLUORESCENCE SPECTRAL FEATURES OF NORMAL SKIN – BASIS FOR COMPARISON WITH CUTANEOUS PATHOLOGIES

Ekaterina Borisova
“Biophotonics” lab., Institute of Electronics, Bulgarian Academy of Sciences
72, Tsarigradsko chaussee blvd., 1784 Sofia, Bulgaria

ABSTRACT

Optical biopsy is relatively new term used in medical practice for description of fluorescence and/or reflectance spectroscopy of human tissues in vivo. Painless, instant diagnoses from optical biopsies will soon be a reality. These forms of optical diagnoses are preferable to the removal of several square centimeters of tissue surface - common in traditional biopsies – followed by delays while samples are sent for clinical analysis. There is also possible that the optical biopsy apparatus will requires a learning curve of several practice attempts, compared to years of training needed for more conventional techniques. Autofluorescence spectroscopy of human tissues is very attractive tool for early diagnosis of cancer due to its high sensitivity, easy-to-use methodology for measurements, lack of need for contrast agents’ application on the tissue under investigation, possibilities for real time measurements and noninvasive tumor detection. However, till our days, no reliable and universal system for fluorescence detection of skin cancer has not appeared on the medical market. Problems for development of such diagnostic fluorescence system for skin cancer detection are related to the great variety of benign and malignant forms of skin pathologies, for example basal cell carcinoma lesions have more than 15 sub-types, squamous cell carcinoma lesions, have about 10 different subtypes, and all of them have variety of benign and dysplastic forms, as well as they are different, including by their fluorescence properties, on different stages on the lesion growth. Other very important disadvantage is the fact that under different excitation wavelengths – different endogenous fluorophores appear in the integral autofluorescence signal coming from the skin, which makes this kind of spectra uneasy for analysis and comparison with the fluorescence signals, detected from various pathological lesions of the skin.
Many authors work with the autofluorescence spectroscopy for early detection of cutaneous pathologies. Different research groups are applied variety of excitation sources (and wavelengths) to stimulate autofluorescence emission from the skin tissues in vivo. Excitation sources applied in such kind of investigations are lasers, LEDs, narrow filtered broad-band lamps. However, a broad survey of the autofluorescence spectra from normal human skin in vivo, which are obtained on different excitation wavelengths, is not observed in the literature.
We will present such investigation, based on detection of excitation-emission matrices (EEMs) of autofluorescence of normal human skin in vivo. Excitation applied is in the region from 250 to 550 nm, with 5 nm step between the excitation bands (2 nm), and emission is detected in the 260-800 nm region, using FluoroLog3 spectrofluorimetric system in steady-state regime of the work with F3000 – fiber-optic stand and probe, attached to the spectrometric system (HORIBA JobinYvon, France). In the EEMs obtained one could address all major skin fluorophores, existing in the normal cutaneous tissues detected in vivo, based on their coordinates (excitation max; emission max). In such a way we obtain a complete picture of the autofluorescence properties of Caucasian normal skin in vivo and could use the received spectral matrices for the next comparison and diagnostic basis with different cutaneous pathologies’ autofluorescence signals.
Acknowledgments: This work was supported by the National Science Fund of Bulgaria of the Ministry of Education, Youth and Science under grant #DMU-03-46/2011.

Representing author

photo

Dr. Ekaterina Georgieva Borisova

Institute of Electronics, Bulgarian Academy of Sciences, Associate Professor
Sofia, Bulgaria

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