Leonardo Marmo Moreira

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.

Photodynamic therapy for pathogenic fungi.

Photodynamic therapy (PDT) is a minimally invasive approach, in which a photosensitiser compound is activated by exposure to visible light. The activation of the sensitiser drug results in several chemical reactions, such as the production of oxygen reactive species and other reactive molecules, whose presence in the biological site leads to the damage of target cells. Although PDT has been primarily developed to combat cancerous lesions, this therapy can be employed for the treatment of several conditions, including infectious diseases. A wide range of microorganisms, including Gram positive and Gram negative bacteria, viruses, protozoa and fungi have demonstrated susceptibility to antimicrobial photodynamic therapy. This treatment might consist of an alternative to the management of fungal infections. Antifungal photodynamic therapy has been successfully employed against Candida albicans and other Candida species and also against dermatophytes. The strain‐dependent antifungal effect and the influence of the biological medium are important issues to be considered. Besides, the choice of photosensitiser to be employed in PDT should consider the characteristics of the fungi and the medium to be treated, as well as the depth of penetration of light into the skin. In the present review, the state‐of‐the‐art of antifungal PDT is discussed and the photosensitiser characteristics are analysed.

Photodynamic Antifungal Therapy Against Chromoblastomycosis

Photodynamic therapy (PDT) is a minimally invasive approach, in which a photosensitizer compound is activated by exposure to light. The activation of the sensitizer drug results in several chemical reactions, such as the production of reactive oxygen species and other reactive molecules, which presence in the biological site leads to the damage of target cells. Although PDT has been primarily developed to combat cancerous lesions, this therapy can be employed for the treatment of several conditions, including infectious diseases. A wide range of microorganisms, including Gram-positive and Gram-negative bacteria, viruses, protozoa, and fungi, have demonstrated susceptibility to antimicrobial PDT. This treatment might consist in an alternative for the management of fungal infections. Antifungal photodynamic therapy has been successfully employed against Candida species, dermatophytes, and Aspergillus niger. Chromoblastomycosis is an infection that involves skin and subcutaneous tissues caused by the traumatic inoculation of dematiaceous fungi species, being that the most prevalent are Fonsecaea pedrosoi and Claphialophora carrionii. In the present work, the clinical applications of PDT for the treatment of chromoblastomycosis are evaluated. We have employed methylene blue as photosensitizer and a LED (Light Emitting Diode) device as light source. The results of this treatment are positive, denoting the efficacy of PDT against chromoblastomycosis. Considering that great part of the published works are focused on in vitro trials, these clinical tests can be considered a relevant source of information about antifungal PDT, since its results have demonstrated to be promising. The perspectives of this kind of treatment are analyzed in agreement with the recent literature involving antifungal PDT.

Raman spectroscopy: A powerful technique for biochemical analysis and diagnosis

The present work focuses on the recent applications of Raman spectroscopy (RS) on biochemical analysis and diagnosis of several biological materials with or without pathological alterations. Important published works about Raman spectroscopy and its use for medical applications were critically reviewed, including articles form our group in order to evaluate the state of the art of the subject. The potential for sample characterization with RS associated to the possibility of analysisin situ makes this instrumental technique in a very auspicious tool of biochemical analysis. RS can promote a significant improvement in the chemical identification and characterization of biological systems, clinical diagnosis and prognosis regarding several diseases and quality of life of innumerous patients. The spectroscopic evaluation is based on the analysis of the Raman spectrum regarding the identification of fingerprint bands of main biological macromolecules, such as nucleic acids, proteins and fat, present in the tissue structure. This review evaluates the employment of RS in diagnosing such pathological manifestations as well as the efforts focused on the instrumental development to biomedical applications. Furthermore, advantages and limitations of this kind of approach are discussed in order to improve the biochemical analysis and diagnosis of several diseases.

Assessment of the genetic risks of a metallic alloy used in medical implants

The use of artificial implants provides a palliative or permanent solution for individuals who have lost some bodily function through disease, an accident or natural wear. This functional loss can be compensated for by the use of medical devices produced from special biomaterials. Titanium alloy (Ti-6Al-4V) is a well-established primary metallic biomaterial for orthopedic implants, but the toxicity of the chemical components of this alloy has become an issue of concern. In this work, we used the MTT assay and micronucleus assay to examine the cytotoxicity and genotoxicity, respectively, of an extract obtained from this alloy. The MTT assay indicated that the mitochondrial activity and cell viability of CHO-K1 cells were unaffected by exposure to the extract. However, the micronucleus assay revealed DNA damage and an increase in micronucleus frequency at all of the concentrations tested. These results show that ions released from Ti-6Al-4V alloy can cause DNA and nuclear damage and reinforce the importance of assessing the safety of metallic medical devices constructed from biomaterials.

Phenotiazinium Dyes as Photosensitizers (PS) in Photodynamic Therapy (PDT): Spectroscopic Properties and Photochemical Mechanisms

© 2012 Moreira et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Phenotiazinium Dyes as Photosensitizers (PS) in Photodynamic Therapy (PDT): Spectroscopic Properties and Photochemical Mechanisms

Influência de diferentes sistemas de solvente água-etanol sobre as propriedades físico-químicas e espectroscópicas dos compostos macrocíclicos feofitina e clorofila α

INFLUENCE OF DIFFERENT WATER-ETHANOL SOLVENT SYSTEMS ON THE SPECTROSCOPIC AND PHYSICO-CHEMICAL PROPERTIES OF THE MACROCYCLIC COMPOUNDS PHEOPHYTIN AND CHLOROPHYLL a. This work focus on the influence of solvent on the photophysical properties of chlorophyll a and pheophytin. Both compounds are related to the photosynthesis process and are considered prototypes of photosensitizers in Photodynamic Therapy. Fluorescence measurements were developed using water/ethanol mixtures at different compositions, since both solvents could be employed in biological applications. The spectroscopic properties of these compounds undergo profound changes depending on water content in the ethanol due to auto-aggregation processes. The major hydrophobicity and the lower dielectric constant of ethanol when compared with water precluded significantly the auto-aggregation process of these compounds.Keywords: chlorophyll a; pheophytin; aggregation.This work focus on the influence of solvent on the photophysical properties of chlorophyll α and pheophytin. Both compounds are related to the photosynthesis process and are considered prototypes of photosensitizers in Photodynamic Therapy. Fluorescence measurements were developed using water/ethanol mixtures at different compositions, since both solvents could be employed in biological applications. The spectroscopic properties of these compounds undergo profound changes depending on water content in the ethanol due to auto-aggregation processes. The major hydrophobicity and the lower dielectric constant of ethanol when compared with water precluded significantly the auto-aggregation process of these compounds.

In vitro photodynamic therapy against Foncecaea pedrosoi and Cladophialophora carrionii

Photodynamic therapy (PDT) has been originally developed for cancer treatment, but recently, it has been successfully employed against microorganisms, including fungi. Chromoblastomycosis is a subcutaneous fungal infection that is recalcitrant to conventional antifungal drug therapy. The most frequent species involved are Foncecaea pedrosoi and Cladophialophora carrionii. The present study aimed to verify the efficacy in vitro of PDT employing methylene blue (MB) as a photosensitiser and Light emmiting diode (LED) (InGaAl) as the light source. Methylene blue at the concentrations of 16, 32 and 64 μg/mL and LED (InGalP) were employed for 15 min against spores of two isolates of F. pedrosoi and two isolates of C. carrionii. The spores were plated on Sabouraud Dextrose agar and the number of colony forming units was counted after 7–10 days of incubation at 37 °C. The PDT with MB and LED was efficient in reducing the growth of all samples tested. Better results were obtained for the concentration of 32 μg/mL of MB. The treatment proved to be highly effective in killing the samples of F. pedrosoi and Cladophialophora pedrosoi tested in vitro. PDT arises as a promising alternative for the treatment of this subcutaneous infection.

Optimizing the Raman signal for characterizing organic samples: The effect of slit aperture and exposure time

The present work is focused on the influence of the slit aperture and time exposure of the infrared light on the Charge Coupled Device (CCD) in relation to their physical effects, in order to improve the Raman spectrum characteristics. Indeed, the alterations in slit aperture and CCD time exposure affect significantly important spectral properties, such as the spectral intensity, Signal to Noise Ratio (SNR) and band width resolution of the Raman spectra. Therefore, the present proposal has the aim of to found the optimum conditions of instrumental arrangement, involving the minimum collection time and maximum signal quality in dispersive Raman spectrometers. Samples of dehydrated human teeth and naphthalene were evaluated with a Raman dispersive spectrometer employing excitation wavelength of 830 nm in several integration times and spectrometer slit apertures. The analysis of the spectral intensity, SNR and band width of selected Raman peaks allowed to infer that these properties of a dispersive Raman spectrum depend directly of the exposure time on the detector as well as spectrograph slit aperture. It is important to register that the higher SNR was obtained with higher exposure time intervals. To the samples evaluated in the present article, the band width has lower values for slit apertures of 100-150 µm, i.e., in this aperture range the spectral resolution is maximum. On the other hand, the intensity and SNR of the Raman spectra becomes optimal for slit apertures of 150-200 µm, since this aperture does not affect significantly the integrity of the Raman signal. In this way, we can to propose that in approximately 150 µm, it is possible to obtain an optimum condition, involving spectral resolution as well as SNR and spectral intensity. In any case, depending of the priorities of each spectral measurement, the instrumental conditions can be altered according with the necessities of each specific chemical analysis involving a determined sample. The present data are discussed in details in agreement with recent data from literature.

Determination of sucrose concentration in lemon-type soft drinks by dispersive Raman spectroscopy

The objective of this study was to quantify the sucrose amount in commercial lemon-type soft drinks through dispersive Raman spectroscopy, comparing the amount listed in the nutritional table of each product to the predicted by a least-square model, in order to obtain a method for quality assurance applied to soft drinks. A dispersive Raman spectrometer was employed using 830 nm laser and imaging spectrograph coupled to a CCD camera, and a total of 48 samples from four brands of lemon-type soft drinks were analyzed. A calibration curve using sucrose from refined sugar (sugarcane) diluted in spring water was elaborated in the range between 0 and 15.0 g/100 ml, and a quantification model based on Partial Least Squares (PLS) regression was developed to correlate the Raman spectra and the amount of sucrose in each dilution. Then, the sucrose in each soft drink sample was predicted employing the calibration curve. The mean error of calibration for the PLS method was 0.30 g/100 ml (3.0%). Results indicated that soft drinks samples have predicted sugar content ranging from 8.1 to 10.9 g/100 ml, with an error of the predicted value compared to the nutritional table ranged from 1.1% to 5.5%. Therefore, Raman spectroscopy in association with PLS regression was an effective method for quantifying the sucrose, with small prediction error. Thus, the present work allows to infer auspicious possibilities of Raman spectroscopy application in the quantification of relevant nutritional facts in beverages.