| dc.description | Methylene blue (MB) is a well-known photosensitizer (Ps) commonly used for antimicrobial
photodynamic therapy (aPDT). Usually aPDT paramenters evaluation involves Ps
concentration, its quantum yield for singlet oxygen production (Type II reaction) and the Ps
photobleaching rate as a function of the deliveried fluence plus oxygen concentration and
consumption on the medium. The role of power density is not often consider.The aim of this
study is to evaluate the role of power density over MB photobleaching dynamcs evaluating the
dimer/monomer ratio as well as the leuco MB formation under discrete changes in power
density keeping the same light fluence. The MB was irradiated using a ?? = 660nm diode laser
(TwinLaser, MMOptics, S??o Carlos, Brazil), 40mW adjustable from 10 to 10mW, 0.04cm2
??? The
powers of 10mW, 20mW, 30mW and 40mW were used for 300s, 150s, 100s and 75s
respectively. The irradiations were carried out directly in a cover quartz cuvette with an optical
path of 1 em. An acrylic mask was made to ensure the coincidence between the irradiation and
the reading points. The readings were made from ?? = 200nm to ?? = 700nm and analyzed in
appropriate software. The DA (dimer absorption) /MA (monomer absarption) was calculated
and the ratio between visible and ultraviolet absorption was aIs o calculated. Figure 1 show the
result afDA/MA for the different irradiances. Our results demonstrated that discrete changes in light irradiance leads to different dinamiccs .
terms ofphotobleaching and DAIMA ratio. | |
