This study compares the transmission of LED and laser light in tissue samples containing the photosensitizer methylene blue for use in photodynamic therapy (PDT). Collagen samples containing methylene blue were irradiated with LED and laser light sources at 660nm and 100mW, and the degradation of methylene blue was analyzed. The results showed that laser light caused more degradation of methylene blue than LED light due to laser light being more efficiently absorbed. However, increasing the energy of LED light could produce similar results to laser light, though it may cause more heating and energy consumption.

1. Abstract. This project proposes compare LED and laser light transmission in
tissue model samples containing methylene blue. Due to the crescent availability
of light sources used on phototherapy, this project aims to help user to choose
and use the devices for a better therapeutic efficiency.
Keywords: light-tissue interaction, photodynamic therapy, LED, laser
INTRODUCTION
The use of light sources to treat diseases is widespreading not only in medicine,
but also in dentistry, physiotherapy and podology. Nowadays, the most used
light sources are LED and laser.
They are used to treat, for example, diabetic foot with photodynamic therapy
(PDT), where a photosensitizer (FS) is activated by light, generating oxygen
reactive species, capable to kill malignant cells and microorganisms [1,2].
OBJECTIVE
Compare LED and laser light transmission in collagen samples containing the FS
methylene blue (MB) to ensure treatment efficacy according to dosimetric
parameters available on literature.
MATERIAL AND METHODS
Fig. 1 Typical evolution of patients in the group treated with PDT. A) Start of the
treatment: middle toe with ulcerated lesions B) The same toe after four months
of PDT treatment [3].
LED AND LASER LIGHT TRANSMISSION STUDY
FOR PDT APPLICATION
Valter Valentim Lula Júnior (valter.junior@ufabc.edu.br)
Universidade Federal do ABC (UFABC) - Rua Arcturus, 03 - Jardim Antares, São Bernardo do Campo - SP - Brasil
15th International Photodynamic Association World Congress – Rio de Janeiro, Brazil - May 22 to 26, 2015
MB
2.4 10-5 g/mL
1 mL of
sample
Cuvette
l = 1cm
laser 660 nm
100 mW
collagen
0.1 g/mL
LED 660 nm
100 mW
fluorescence
analysis
2 samples with 1cm²
of irradiation surface
A
RESULTS
CONCLUSION
It seems that laser is more efficient because its broadband is more utilized.
Nevertheless, with more energy, LED could have the same result than laser, but it
can cause more heating, energy comsumption and scattering.
ACKNOWLEDGMENTS
To CEPOF for the laboratorial support.
REFERENCES
1. Jori G. Tumour photosensitizers: approaches to enhance the selectivity and efficiency of
PDT. J Photochem Photobiol B, v. 36, p.87-93, 1996.
2. Daghastanli, N. A. et al. Photocytotoxicity of a 5-nitrofuranethenyl-quinoline antiseptic
(Quinifuryl) to P388 mouse leukemia cells. Braz. J. Medical Biological Research, v. 37, n. 12, p.
1873-1879, 2004.
3. Tardivo, J. P. et al. A clinical trial testing the efficacy of PDT in preventing amputation in
diabetic patients. Photodiagnosis Photodyn Ther, v. 11, p. 342-350, 2014
Fig. 4 MB degradation for LED and laser
According to Figure 4, laser causes more MB degradation than LED, operating at
100 mW/cm². Considering that laser energy is absorbed with 90% efficiency for
each minute of irradiation, its fluence is 5.4 J/cm².
At 100 mW/cm², LED efficiency on degradation is lower because part of light,
approximatelly 40%, is not utilized (Figure 5). Therefore its fluence is 3.4 J/cm².
Aproximating the LED source from the sample, its energy on sample surface is
multiplied by three, resulting on a fluence of 9.72 J/cm².
Fig. 5 Methylene blue absorbance
spectrum with LED and laser irradiation
broadband
Fig. 3 A) LED and laser irradiation B) Cuvette with MB C)
irradiation profile throught cuvette
B
C
A
Fig. 2 Arrangement for irradiation and fluorescence analysis