Growth models of fractal interfaces in the description of microorganism colony growth: effect of photodynamic inactivation.

Candida albicans is responsible for most of the nosocomial infections that affect immunocompromised individuals. We investigated the application of eosin in photodynamic inactivation as a strategy in the inhibition of the growth of C. albicans and the morphological variation and growth dynamics in light of fractal theory. The damage caused to fungal structures alters the roughness of the colony, and these changes were described by parameters that were defined by mathematical models. Proliferation of the fungi should be inhibited in the center of the colonies and the analysis of the edges gives an indication about the dynamics of growth and cell reproduction.

Latex membranes with methylene blue dye for antimicrobial photodynamic therapy.

The search for new materials that can be applied in the treatment of injured human tissues has led to the development of new dressings. Membranes have potential as dressing materials because they can be fitted to and interact with the tissue surface. In this study, we analyze the morphological properties and wettability of latex membranes, along with the incorporation of the photosensitizer methylene blue, in the context of the utility of the membranes in curative applications involving photodynamic therapy (PDT). It was observed that deposition of the photosensitizer into latex membranes increased both the surface roughness and wettability. Antifungal testing indicated that antimicrobial PDT assisted by the latex membranes incorporating methylene blue effectively inactivated Candida albicans.

The role of xenobiotic-metabolizing enzymes in the placenta: a growing research field.

Introduction: The placenta is a temporary and unique organ that allows for the physical connection between a mother and fetus; this organ regulates the transport of gases and nutrients mediating the elimination of waste products contained in the fetal circulation. The placenta performs metabolic and excretion functions, on the basis of multiple enzymatic systems responsible for the oxidation, reduction, hydrolysis, and conjugation of xenobiotics. These mechanisms give the placenta a protective role that limits the fetal exposure to harmful compounds. During pregnancy, some diseases require uninterrupted treatment even if it is detrimental to the fetus. Drugs and other xenobiotics alter gene expression in the placenta with repercussions for the fetus and mother's well-being.Areas covered: This review provides a brief description of the human placental structure and function, the main drug and xenobiotic transporters and metabolizing enzymes, placenta-metabolized substrates, and alterations in gene expression that the exposure to xenobiotics may cause.Expert opinion: Research should be focused on the identification and validation of biological markers for the assessment of the harmful effects of some drugs in pregnancy, including the evaluation of polymorphisms and methylation patterns in chorionic villous samples and/or amniotic fluid.

Fractal analysis and mathematical models for the investigation of photothermal inactivation of Candida albicans using carbon nanotubes.

Candida albicans is responsible for the majority of nosocomial infections affecting immunocompromised patients. Systemic antifungals may promote microbial resistance, which has led to the search for alternative treatments, such as photothermal therapy (PTT). PTT assumes that the interaction of electromagnetic radiation with a photothermal agent generates heat that can lead to the destruction of tumor cells and the death of microorganisms. Carbon nanotubes (CNTs) have the potential for applications in biomedical systems, including acting as controlled deliverers of drugs, biosensors and scaffolds for tissue engineering and regenerative medicine. Furthermore, the absorption of radiation by CNTs in the infrared region induces an increase in temperature, which makes CNTs candidates for photothermal agents. In this work, the photothermal inactivation of C. albicans was evaluated by multiple wall CNTs associated with laser radiation in the near-infrared region. The mechanisms that are involved in inactivation were evaluated through cell susceptibility studies and an analysis of microscopic images that are associated with mathematical models and fractal concepts. The results indicate that direct contact between the cells and CNTs without irradiation does not lead to cell death, whereas the laser-mediated process is effective in inactivation. The application of the laws of scale and fractal concepts indicate that in the control groups, there are two distinct regimes that are delimited by the mean diameter of the microorganisms, as described by the Eden model and by the quasi-Euclidean surface. For the irradiated groups, the surfaces present only one regime described by Kardar-Parisi-Zhang, KPZ. The analysis of the fractality of the system by mathematical models can help in the identification of new strategies for the inactivation of microorganisms.

Immobilization of triclosan and erythrosine in layer-by-layer films applied to inactivation of microorganisms.

The use of layer-by-layer (LbL) deposition technique allows materials, such as drugs, to be self-assembled in multilayers with other electrolytes by combining their properties in a nanostructured system. Triclosan (TCS) is commonly used as a drug because of its bactericidal action, while erythrosine (ERY) has been used as a photosensitizer in photodynamic therapies because of its high light absorptivity in the visible region of the electromagnetic spectrum. The major advantage of investigating systems immobilized in LbL films is the benefit of characterizing the interaction through available substances in solid state techniques. It was possible to immobilize in LbL films, ERY, and ERY + TCS. The results show that the growth of the films was linear, indicating the deposition of the same amount of material from the first bilayer without substrate interference. The release analysis showed slow kinetics, which occurred more rapidly for ERY LbL films, probably due to apparent activation energy, which were higher for films with TCS. The combination of TCS, ERY, and laser light (532 nm) for photodynamic inactivation of the fungus Candida albicans was analyzed, and the results were promising for future studies in applications, such as coating surfaces of dental implants.

Incorporation of triclosan and acridine orange into liposomes for evaluating the susceptibility of Candida albicans.

Candida albicans is responsible for many of the infections affecting immunocompromised individuals. Although most C. albicans are susceptible to antifungal drugs, uncontrolled use of these drugs has promoted the development of resistance to current antifungals. The clinical implication of resistant strains has led to the search for safer and more effective drugs as well as alternative approaches, such as controlled drug release using liposomes and photodynamic inactivation (PDI), to eliminate pathogens by combining light and photosensitizers. In this study, we used layer-by-layer (LBL) assembly to immobilize triclosan and acridine orange encapsulated in liposomes and investigated the possibility of controlled release using light. Experiments were carried out to examine the susceptibility of C. albicans to PDI. The effects of laser irradiation were investigated by fluorescence microscopy, atomic force microscopy, and release kinetics. Liposomes were successfully prepared and immobilized using the self-assembly LBL technique. Triclosan was released more quickly when the LBL film was irradiated. The release rate was approximately 40% higher in irradiated films (fluence of 15J/cm2) than in non-irradiated films. The results of the susceptibility experiments and surface morphological analysis indicated that C. albicans cell death is caused by photodynamic inactivation. Liposomes containing triclosan and acridine orange may be useful for inactivating C. albicans using light. Our results lay the foundation for the development of new clinical strategies to control resistant strains.

Immobilization of chlorophyll by using layer-by-layer technique for controlled release systems and photodynamic inactivation.

The development of systems for the controlled release of drugs is important because they allow the control of drug absorption and tissue distribution and also can reduce local toxicity. This study aimed to assemble and characterize two types of release systems, consisting of layer-by-layer films obtained from poly(allylamine) hydrochloride with chlorophyll (PAH/CHL films) or chlorophyll incorporated into dipalmitoylphosphatidylcholine liposomes (PAH/Lip+CHL films). For these systems, the molecular aggregation, growth process, thermally stimulated desorption, wettability, and controlling release of CHL was studied by using UV-vis spectroscopy and wetting contact angle analysis. In addition, experiments of photodynamic inactivation using PAH/CHL or PAH/Lip+CHL films with a 633-nm laser light were performed and the susceptibility of Candida albicans (C. albicans) to this approach was examined. Fluorescence and atomic force microscopies were used to investigate the surface morphology after the application of the photoinactivation procedure. A redshift of the UV-vis spectrum associated to films when compared with the spectrum of the CHL solution indicated a molecular aggregation of CHL molecules in the films. The film growth process was determined by a nucleation and a growth of spheroids or rods for either PAH/Lip+CHL or PAH/CHL films, respectively. Thermally activated desorption experiments indicated that interactions between CHL and PAH (126kJ/mol) in PAH/CHL or between Lip+CHL and PAH (140kJ/mol) in PAH/Lip+CHL films may be governed by electrostatic interactions. The wettability of PAH/Lip+CHL films was larger than that for PAH/CHL films, which can be attributed to hydrophilic groups on the surface of the DPPC liposomes. Release experiments revealed that free CHL in PAH/CHL films was released more slowly than its partner incorporated into liposomes. After the photodynamic inactivation, results of survival fraction and fluorescence microscopy revealed that C. albicans presented similar susceptibility for the two kinds of films. AFM supported the fluorescence one suggesting that cell death of C. albicans may occur due to damages to its cell wall by C. albicans.

Spray layer-by-layer films for photodynamic inactivation.

BACKGROUND: A novel approach for photodynamic inactivation of Candida albicans is proposed. This method consists of realizing inactivation using ultraviolet light (254nm) combined with spraying layer-by-layer films of acridine orange. METHODS: To evaluate the effectiveness of the approach, the C. albicans were immobilized on quartz slices and covered with the spray layer-by-layer films. The fungi were analyzed using experiments to determine cell viability, as well as by fluorescence and atomic force microscopy. RESULTS: Viability analysis of C. albicans after photodynamic inactivation assisted by the films indicates cell death. The extent of cell death increases as the number of film layers increases. Fluorescence and atomic force microscopy analyses corroborated the cell death of C. albicans, which is posited to be due to damages to the fungi cell wall. CONCLUSIONS: Our approach has the potential to be used as an alternative for photodynamic inactivation of C. albicans. In addition, this method could be used in clinical procedures, such as for the decontamination of medical devices.

Oxidative and nitrosative stress on phagocytes' function: from effective defense to immunity evasion mechanisms.

Although oxygen, nitrogen, and chlorine reactive species have been associated with disease pathogenesis, their partial absence is very harmful to the body's innate immune defense. Lacking of adequate release of free radicals from activated phagocytes is related to impaired ability on fungi, bacteria, and protozoa killing. We constructed an updated conceptual landmark regarding the paramount role of free radicals in phagocyte defense systems (phagocyte oxidase, myeloperoxidase, and nitric oxide/peroxynitrite system) on natural immunity. Diverse fungal, bacterial and protozoal pathogens evade the phagocytes' oxidative/nitrosative burst though antioxidant genes, enzymes and proteins. The most important evasion mechanisms were also described and discussed. These interconnected systems were reviewed and discussed on the basis of knowledge from relevant research groups around the globe. Phagocyte-derived free radicals are essential to destroy important human pathogens during the course of innate immunity.

Programmed cell death in thymus during experimental paracoccidioidomycosis.

Many works have shown that immunosuppressive effects induced by systemic mycosis can be related to primary lymphoid organ damage. Previous studies in our laboratory showed that Paracoccidioides brasiliensis was able to invade the thymus, inducing a severe atrophy with significant reduction of cortical area along with a loss of cortico-medullary boundary. The objective of the present study was to investigate whether thymic atrophy is caused by programmed cell death (PCD) and to examine the ultrastructural characteristics of the thymus in experimentally infected BALB/c mice. The results revealed an eightfold increase in the apoptotic index occurring by day 5 post infection, i.e., during early stages of the infection, shown by immunohistochemistry. In addition, typical cell alterations of autophagic PCD were observed by transmission electron microscopy. Taken together, these results reinforce the idea that thymic alterations may be involved in the immunosuppressive phenomenon frequently associated with paracoccidioidomycotic infection.

Early histopathological changes in bone marrow of Paracoccidioides brasiliensis-infected mice

The involvement of bone marrow in the pathology of experimental P. brasiliensis infection in BALB/c mice was investigated. The histopathological features of bone marrow induced by the fungus were correlated with hematological changes in peripheral blood from 1 to 28 days post-infection. Intense lymphopenia and moderate neutrophilia were detected. The early changes in bone marrow included (i) maturation arrest characterized by an increase immature blood cell precursors, mainly of granulocytic origin, (ii) intense vascular congestion when compared with the vessels of normal marrow, and (iii) an increased number of megakaryocytes. The normal histological pattern of bone marrow was restored by 28 days post-infection. No histologically recognizable lesion, such as granuloma formation or an abnormal cellular infiltrate, which could indicate the presence of the P. brasiliensis in bone marrow, was observed. In addition, special stains were unable to detect the fungus. The mechanisms responsible for the alterations described here are still unclear but are probably related to more general phenomena affecting the host rather than the direct damage of the precursors cells by P. brasiliensis.