Antonio Eduardo da Hora Machado

Terapia Fotodinâmica: Princípios, Potencial de Aplicação e Perspectivas

Photodynamic Therapy (PDT) has been designated as a promising new modality in the treatment of cancer and other diseases since the early 1980s. It has been used with success for the treatment of a variety of tumours, and attempts are being made to extend this treatment modality to other clinical conditions (as example, the inactivation of viruses in blood and blood components). This can be partly attributed to the very attractive basic concept of PDT: the combination of a photosensitizing drug and light, which are relatively harmless by themselves but combined (in the presence of oxygen) ultimately cause more or less selective tumour destruction.

Photocatalytic degradation of lignin and lignin models, using titanium dioxide: the role of the hydroxyl radical.

The role of hydroxyl radicals on the degradation of lignins during a cellulosic pulp bleaching process including a photocatalytic stage, was assessed using peroxyformic acid lignins EL1 and REL1 and two phenolic niphenyl lignin models 1 and 2. The irradiations were performed in the absence of photocatalyst TiO2 and H2O2 (condition a), in the presence of TiO2 (condition b) and in the presence of H2O2 (condition c). The experiments were conducted in alkaline (pH approximately 11) aqueous ethanol solutions with oxygen bubbling. The relative phenolic content of the irradiated solutions, which is indicative of the involvement of hydroxyl radicals, was determined by ionization absorption spectroscopy. The results obtained show that the catalyzed reaction involves both degradation of the phenolate groups by electron transfer and hydroxylation of the lignin aromatic structure. Benzyl alcohol structural elements in sodium borohydride reduced lignin REL1 and compound 2 were also found as good trapping agents for the hydroxyl radicals. The degradation of EL1 was studied by measuring its fluorescence emission by comparison to the fluorescence of compound 2. The emission spectra indicate that some biphenyl phenolate anions in EL1 are reacting under UV/visible irradiation and some others, probably polyphenolic chromophores emitting less fluorescence, are formed.

Degradation of caffeine by photo-Fenton process: optimization of treatment conditions using experimental design.

The degradation of caffeine in different kind of effluents, via photo-Fenton process, was investigated in lab-scale and in a solar pilot plant. The treatment conditions (caffeine, Fe(2+) and H(2)O(2) concentrations) were defined by experimental design. The optimized conditions for each variable, obtained using the response factor (% mineralization), were: 52.0 mg L(-1)caffeine, 10.0 mg L(-1)Fe(2+) and 42.0 mg L(-1)H(2)O(2) (replaced in kinetic experiments). Under these conditions, in ultrapure water (UW), the caffeine concentration reached the quantitation limit (0.76 mg L(-1)) after 20 min, and 78% of mineralization was obtained respectively after 120 min of reaction. Using the same conditions, the matrix influence (surface water - SW and sewage treatment plant effluent - STP) on caffeine degradation was also evaluated. The total removal of caffeine in SW was reached at the same time in UW (after 20 min), while 40 min were necessary in STP. Although lower mineralization rates were verified for high organic load, under the same operational conditions, less H(2)O(2) was necessary to mineralize the dissolved organic carbon as the initial organic load increases. A high efficiency of the photo-Fenton process was also observed in caffeine degradation by solar photocatalysis using a CPC reactor, as well as intermediates of low toxicity, demonstrating that photo-Fenton process can be a viable alternative for caffeine removal in wastewater.

Characterization and Evaluation of the Efficiency of TiO2/Zinc Phthalocyanine Nanocomposites as Photocatalysts for Wastewater Treatment Using Solar Irradiation

This work reports the characterization of composites prepared by the association between zinc phthalocyanine (ZnPc) and titanium dioxide. These composites are better photocatalysts for wastewater decontamination mediated by solar radiation than pure TiO2, performance that remains even when reused. The UV-Vis diffuse reflectance absorption spectra show for these composites two intense absorption bands. The first covers the ultraviolet and part of the visible spectrum region until 460 nm (2.7 eV), whereas the second, nonstructured, goes from 475 nm until the near infrared with an absorption peak at 683 nm attributed to the Q band of ZnPc. The production of additional e−/h

Peroxyformic Acid Pulping of Eucalyptus Grandis Wood Chips and Sugar Cane Bagasse in one Stage and Characterization of the Isolated Lignins

Abstract An improvement in the peroxyformic acid process for the production of chemical pulps from Eucalyptus grandis wood chips and sugar cane bagasse is described. The pulping of these lignocellulosics was carried out in a single stage at 75°C (3 h) in order to benefit from the action of the peroxyformic acid and a subsequent formic acid reflux (110°C, 2 h), using the same liquor. Efficient distillation of the spent liquor allowed recovery of a large quantity of formic acid and phenolic lignin, the latter obtained after mild saponification, followed by precipitation in acidic media. The pulping process was completed with a 0.25M NaOH extraction of the pulp at 60°C to dissolve more lignin. Good quality unbleached pulps were obtained. Kappa numbers (KN) of 14 and 13, and intrinsic viscosities [n] of 1130 and 980 dm3. Kg−2 were obtained, respectively, for E. grandis and sugar cane bagasse. The structures of the lignin fractions were studied by size exclusion chromatography; methoxyl content analysis; eleme...

The photodegradation of lignins in the presence of hydrogen peroxide

Abstract The photodegradation of lignins in solutions containing hydrogen peroxide was studied. At basic pH, the reaction is at least seven times more efficient than in acid solution, where only hydroxyl radicals are formed. Evolution of carbon dioxide and loss of mass can be observed in basic solution. The role of certain functional groups was determined: α-carbonyls and phenols favour decomposition, and their reduction of derivatization leads to a decrease in the photodegradation efficiency. The presence of carboxylate groups and an increase in molecular weight lead to a decrease in the reaction efficiency. Evidence for the participation of singlet oxygen as a reactive species, in the reactions of alkaline pH, generated by the decomposition of hydrogen peroxide, is presented.

Spectrofluorimetric Determination of Second Critical Micellar Concentration of SDS and SDS/Brij 30 Systems

Potentially useful stead-state fluorimetric technique was used to determine the critical micellar concentrations (CMC1 and CMC2) for two micellar media, one formed by SDS and the other by SDS/Brij 30. A comparative study based on conductimetric and surfacial tension measurements suggests that the CMC1 estimated by the fluorimetric method is lower than the value estimated by these other techniques. Equivalent values were observed for SDS micelles without Brij 30 neutral co-surfactant. The use of acridine orange as fluorescent probe permitted to determine both CMC1 and CMC2. Based on it an explanation on aspects of micelle formation mechanism is presented, particularly based on a spherical and a rod like structures.

Solar photocatalytic water detoxification of paper mill effluents

To implement solar photocatalytic water detoxification in industrial processes, problems have to be identified. The effluents from paper mills contain non-biodegradable substances like polyphenolic polymer lignin. Photocatalysis is a suitable method to degrade this class of substances. Especially in good solar regions, like Brazil, solar radiation should be ideally used for that process. The German Aerospace Center and the Federal University of Uberlândia-MG, Brazil are cooperating in a project funded by the German International Bureau of the Federal Ministry of Education and Science and CNPq, Brazil to implement solar photocatalysis in the treatment of paper mill effluents. Therefore, the following tasks are worked on: model compounds for the contaminants have been identified and compared to the real effluents. Different photocatalysts and oxidizing agents were tested to shape the degradation process for use in an industrial application. Tests were carried out in lamp reactors as well as in solar reactors to determine the influence of the reactor on the degradation. The kinetic of the degradation was also determined. The test results have shown that the non-biodegradable substances can be very effectively degraded by photocatalytic treatment. Especially in solar reactors like the CPC type reactor, degradation takes place very fast. Total mineralization of the contaminants can be reached. The paper describes the project as well as the test results and will provide an outlook to the implementation of solar photocatalytic detoxification technology in Brazil.

Characterization of PLGA microparticles as a drug carrier for 3-ethoxycarbonyl-2h-benzofuro[3,2-f]-1-benzopyran-2-one. Ultrastructural study of cellular uptake and intracellular distribution.

Here we describe the application of microparticles (MPs) for the delivery and release of the drug a benzopsoralen. We also evaluated the intracellular distribution and cellular uptake of the drug by using an encapsulation technique for therapeutic optimization. MPs containing the compound 3-ethoxycarbonyl-2H-benzofuro[3,2-f]-1-benzopyran-2-one (psoralen A) were prepared by the solvent evaporation technique, and parameters such as particle size, drug encapsulation efficiency, effect of the encapsulation process on the drugs photochemistry, zeta potential, external morphology, and in vitro release behavior were evaluated. The intracellular distribution of MPs as well as their uptake by tissues were monitored. Size distribution studies using dynamic ligh scattering and scanning electron microscopy revealed that the MPs are spherical in shape with a diameter of 1.4 μ m. They present low tendency toward aggregation, as confirmed by their zeta potential (+10.6 mV). The loading efficiency obtained was 75%. As a consequence of the extremely low diffusivity of the drug in aqueous medium, the drug release profile of the MPs in saline phosphate buffer (pH 7.4) was much slower than that obtained in the biological environment. Among the population of peritoneal phagocytic cells, only macrophages were able to phagocytose poly-d,l-lactic-co-glycolic acid (PLGA) MP. The use of psoralen A in association with ultraviolet light (360 nm) revealed morphological characteristics of cell damage such as cytoplasmic vesiculation, mitochondria condensation, and swelling of both the granular endoplasmatic reticulum and the nuclear membrane. These results indicate that PLGA MP could be a promising delivery system for psoralen in connection with ultraviolet irradiation therapy (PUVA).

Photochemical bleaching of chemical pulps catalyzed by titanium dioxide

A two-stage process for photochemical bleaching of cellulosic pulps is presented. The first, based on the generation of oxygen active species by the photocatalytic action of TiOZ, and the second on the photochemical decomposition of hydrogen peroxide. Both stages are carried out under alkaline pH and at 85°C in aqueous suspension at a consistency of 5% The experiments were performed on kraft (Eucul~prus grandis, firms pinasfer and Pica muuiana), acesolv (E. grandis) and peroxyformic acid (E. grandis) pulps. The presence of TiO, as photocatalyst showed several advantages, such as reduction of reaction time, preservation of the pulp viscosity, increase of the selectivity during the photobleaching and decrease of the consumption of the bleaching chemicals. UV/Vis and FHR spectroscopies indicate a decrease of the coniferaldehyde structures during the TiO, photocatalyzed stage, whereas quinones entities were found to remain in the residual lignin even