Laser and Non-laser Light Sources for Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) is an anticancer combination therapy, which requires a photosensitiser, which tends to accumulate preferentially in the tumour, and light. Historically large, complex lasers have been used to carry out PDT treatment. Nowadays there is a wide range of coherent and non-coherent sources that can be used. This paper considers the important characteristics of light sources for PDT, including dye lasers pumped by argon or metal vapour lasers and frequency-doubled Nd:YAG lasers. Non-laser sources including tungsten filament, xenon arc, metal halide and fluorescent lamps are also discussed. New exciting developments such as LEDs and femtosecond lasers are also reviewed. The relative merits of laser and non-laser sources are critically examined.

One- and two-photon activated phototoxicity of conjugated porphyrin dimers with high two-photon absorption cross sections

“…Lasers are the most common light sources for PDT as they can deliver focused intense monochromatic light, although they may be replaced by cheap, powerful (> 1 W) LEDs. 40 There are many methods for measuring cell survival after PDT in vitro. Cell death may be quantified by measuring 140 enzyme activity, 41 membrane permeability 42 or redox potentials.…”

“…The efficiency by which a photosensitiser undergoes two- 40 photon absorption is quantified by its TPA cross-section (! ), measured in Göppert-Mayer units (1 GM = 10 -50 cm 4 s photon -1 molecule -1 ).…”

A aplicação da fotoquímica inorgânica nas diversas áreas da ciência

“…A propagação depende da presença de regiões não-homogêneas, como membranas, núcleos, água ou corantes, que absorvem muita luz, como a melanina e as porfirinas. A fototerapia usa luz compreendida na região de 620-850 nm, onde se observa maior permeabilidade pela pele; por isso, esta região é denominada janela fototerapêutica 23 . Por ex., a região compreendida entre 600-700 nm, constituída principalmente por grupos porfirínicos, tem maior efeito de penetração (>50%) que, por exemplo, a luz de 400-500 nm constituída por grupos flavinas, colágeno, NADH, nicotinamida.…”

“…As fontes de luz mais comuns incluem os lasers de Ar, Kr e He/Ne (colimadas e monocromáticas) e as lâmpadas de arcos de xenônio (não colimadas). Uma vez que as lâmpadas não podem ser acopladas a fibras óticas, elas são restritas a tratamentos de lesões na pele, enquanto o laser é usado para tratamentos endoscópicos 23 .…”

Chemiluminescence as a PDT light source for microbial control

“…Laser sources are so far the first option for the PDT treatment of internal organs as in esophagus, lung and bladder cancers. There are already some portable light sources based on battery, powered systems for PDT treatments [9,10].…”