Salmonella enterica is a gram-negative pathogen with great relevance in the food industry, related to food gastroenteritis. Staphylococcus aureus is a gram-positive bacterium that causes intestinal infection, vomiting, and diarrhea when its toxins are ingested. One way to combat these pathogens is photodynamic inactivation (PDI), which consists of the interaction of three elements: photosensitizer, light and molecular oxygen. This interaction promotes the formation of reactive oxygen species, which leads to cell death through necrosis and apoptosis. The present study was divided into four groups: control, light, photosensitizer, and PDI, in order to evaluate the effect of the individually applied and combined elements. In addition, a comparison between the responses of different types of bacteria was performed. The photosensitizer used was protoporphyrin IX, produced through its precursor aminolevulinic acid (ALA). The ALA was applied at concentrations of 0.4 and 0.7 μM, and incubation time from one to four hours. Irradiation was performed at 630 nm and a fluence of 12, 36 and 72 J/cm<sup>2</sup> . The results indicated that the photosensitizer concentrations were inefficient to cause total cell death, however, gram-positive bacteria were more susceptible to the technique. Photodynamic antimicrobial therapy is an alternative to existing techniques, presenting a great cost-benefit and having the advantage of being ecologically correct since it only involves non-toxic elements to cause the total destruction of the bacteria.
Photodynamic therapy (PDT) and radiotherapy are non-systemic cancer treatment options with different mechanisms of damage. So combining these techniques has been shown to have some synergy, and can mitigate their limitations such as low PDT light penetration or radiotherapy side effects. The present study monitored the induced tissue changes after PDT, radiotherapy, and a combination protocol in normal rat skin, using an optical spectroscopy system to track the observed biophysical changes. The Wistar rats were treated with one of the protocols: PDT followed by radiotherapy, PDT, radiotherapy and radiotherapy followed by PDT. Reflectance spectra were collected in order to observe the effects of these combined therapies, especially targeting vascular response. From the reflectance, information about oxygen saturation, met-hemoglobin and bilirubin concentration, blood volume fraction (BVF) and vessel radius were extracted from model fitting of the spectra. The rats were monitored for 24 hours after treatment. Results showed that there was no significant variation in the vessel size or BVF after the treatments. However, the PDT caused a significant increase in the met-hemoglobin and bilirubin concentrations, indicating an important blood breakdown. These results may provide an important clue on how the damage establishment takes place, helping to understand the effect of the combination of those techniques in order to verify the existence of a known synergistic effect.
Photodynamic therapy (PDT) is a treatment modality that can be indicated for several cancer types and pre-cancer lesions. One of the main applications of PDT is the treatment of superficial skin lesions such as basal cell carcinoma, Bowen’s disease and actinic keratosis. Three elements are necessary in PDT, a photosensitizer (PS); light at specific wavelength to be absorbed by the PS, and molecular oxygen. A typical PS used for skin lesion is protoporphyrin IX (PpIX), which is an intrinsic PS; its production is stimulated by a pro-drug, such as 5-aminolevulinic acid (ALA). Before starting a treatment, it is very important to follow up the PpIX production (to ensure that enough PS was produced prior to a PDT application) and, during a PDT session, to monitor its photodegradation (as it is evidence of the photodynamic effect taking place). The aim of this paper is to present a unique device, LINCE (MMOptics - São Carlos, Brazil), that brings together two probes that can, respectively, allow for fluorescence imaging and work as a light source for PDT treatment. The fluorescence probe of the system is optically based on 400 nm LED (light emitting diodes) arrays that allow observing the fluorescence emission over 450 nm. The PDT illumination probe options are constituted of 630 nm LED arrays for small areas and, for large areas, of both 630 nm and 450 nm LED arrays. Joining both functions at the same device makes PDT treatment simpler, properly monitorable and, hence, more clinically feasible. LINCE has been used in almost 1000 PDT treatments of superficial skin lesions in Brazil, with 88.4% of clearance of superficial BCC.