Photodynamic therapy (PDT) is a technique that combines light’s interaction with a photoactive substance to promote cellular death and that has been used to treat a wide range of maladies. Cancer is among the leading causes of death worldwide and has been a central issue assessed by PDT research and clinical trials over the last 35 years, but its efficiency has been hampered by photosensitizer buildup at treatment site. Nanotechnology has been addressing drug delivery problems by the development of distinct nanostructured platforms capable of increasing pharmacological properties of molecules. The association of nanotechnology’s potential to enhance photosensitizer delivery to target tissues with PDT’s oxidative damage to induce cell death has been rising as a prospect to optimize cancer treatment. In this study, we aim to verify and compare the efficiency of PDT using redox-responsive silica-based nanoparticles carrying protoporphyrin IX (PpIX) in vitro, in both tumor and healthy cells. Dose-response experiments revealed the higher susceptibility of murine melanoma cells (B16-F10 cell line) to PDT (630 nm, 50 J/cm2) when compared to human dermal fibroblasts (HDFn): after 24 h of incubation with 50 μg/mL nanoparticles solutions, approximately 80 % of B16- F10 cells were killed, while similar results were obtained in HDFn cultures when solutions over 150 μg/mL were used. Uptake and ROS generation assays suggest increased nanoparticle internalization in the tumor cell line, in comparison with the healthy cells, and greater ROS levels were observed in B16-F10 cells.
Lower respiratory infections are among the leading causes of death worldwide. In this study, it was evaluated the
interaction of indocyanine green, a photosensitizer activated by infrared light, with alveolar macrophages and the
effectiveness of the photodynamic therapy using this compound against Streptococcus pneumoniae . Initial experiments
analyzed indocyanine green toxicity to alveolar macrophages in the dark with different drug concentrations and
incubation times, and macrophage viability was obtained with the MTT method. The average of the results showed
viability values below 90% for the two highest concentrations. Experiments with Streptococcus pneumoniae showed
photodynamic inactivation with 10 μM indocyanine green solution. Further experiments with the bacteria in co-culture
with AM will be conducted verifying the photodynamic inactivation effectiveness of the tested drug concentrations and
incubation periods using infrared light.
Infectious pneumonia is a major cause of morbidity and mortality, despite advances in diagnostics and therapeutics in
pulmonary infections. One of the major difficulties associated with the infection comes from the high rate of antibiotic
resistant microorganisms, claiming for the use of alternative techniques with high efficiency and low cost. The
photodynamic inactivation (PDI) is emerging as one of the great possibilities in this area, once its action is oxidative, not
allowing microorganism develops resistance against the treatment. PDI for decontamination pulmonary has potential for
treatment or creating better conditions for the action of antibiotics. In this study, we are developing a device to
implement PDI for the treatment of lung diseases with extracorporeal illumination. To validate our theory, we performed
measurements in liquid phantom to simulate light penetration in biological tissues at various fluency rates, the
temperature was monitored in a body of hairless mice and the measurements of light transmittance in this same animal
model. A diode laser emitting at 810 nm in continuous mode was used. Our results show 70% of leakage at 0.5 mm of
thickness in phantom model. The mouse body temperature variation was 5.4 °C and was observed light transmittance
through its chest. These results are suggesting the possible application of the extracorporeal illumination using infrared
light source. Based on these findings, further studies about photodynamic inactivation will be performed in animal model
using indocyanine green and bacteriochlorin as photosensitizers. The pulmonary infection will be induced with
Streptococcus pneumoniae and Klebsiella pneumoniae.
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