Influence of cytochrome P450 3A4 and membrane lipid composition on doxorubicin activity.

Drug resistance is known to depend on the interactions with cell membranes and other molecules such as human cytochromes P450 (CYPs) which are anchored on the endoplasmic reticulum (ER) membrane and involved in the metabolism of anticancer drugs. In this study, we determined the influence from cytochrome P450 3A4 (CYP3A4) on the interaction between the drug doxorubicin (DOX) and Langmuir monolayers mimicking cell membranes. The lipid composition was varied by changing the relative concentrations of cholesterol (Chol), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and L-α-phosphatidylinositol (PI). Three compositions were studied in detail which represented a healthy cell membrane and cancerous cell membranes. DOX induced an expansion in the surface pressure isotherms for all monolayers, with stronger effect for the composition of cancerous cell with a high Chol content, thus confirming the relevance of lipid composition. This effect decreased considerably when CYP3A4 was incorporated with the formation of CYP3A4-DOX complexes, according to results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) measurements. Taken together, these results support the hypothesis of CYP3A4 being involved in drug resistance, which may be exploited to design strategies to enhance chemotherapy efficacy.

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.

Anxiety and burnout symptomatology at the end of medicine career / [Sintomatología de ansiedad y burnout al término de la licenciatura de médico cirujano]

Introduction: Due to the high demands of the medicine career, coupled with students' work and personal obligations, they are a susceptible population to develop anxiety and Burnout syndrome (BS) which can influence their academic performance. The aim of the present study was to determine the prevalence and symptomatology of anxiety and Burnout, as well as to identify their impact on the academic performance of students at the end of their medical degree. Method: A cross-sectional, observational study was conducted on medical students at the end of their degree, using the Trait and State Anxiety inventory, the Maslach Burnout scale, and the grade point average through the Academic Secretary. Results: A prevalence of state anxiety (SA) of 40. 6% and trait anxiety (TA) of 31. 2% was observed, both with similar proportions between a medium and high level (75-25%), with an association between them. The prevalence of BS was 15. 6%, of which 17. 2% and 23. 4% respectively showed high levels of fatigue and depersonalization, moreover, 18. 8% showed low levels of personal fulfillment. Conclusion: At the end of the career, students show symptoms of SA and TA with a high association between them. Therefore, it is important to emphasize that transitory anxiety can become part of an anxious response as a personality trait. The prevalence of BS was low and not related to academic performance, age, or sex.

Introducción: Las altas exigencias que presenta la carrera de medicina, aunado a las obligaciones laborales y personales de los estudiantes, los predispone a desarrollar ansiedad y síndrome de Burnout (SB), lo cual puede influir en su rendimiento académico. El objetivo del presente estudio fue determinar la prevalencia y la sintomatología de ansiedad y Burnout, así como identificar su impacto en el rendimiento académico de los estudiantes al término de la licenciatura en médico cirujano. Método: Se realizó un estudio transversal, observacional en estudiantes de medicina al término de la carrera, se utilizó el inventario de Ansiedad Rasgo y Estado, la escala Maslach Burnout y el promedio de las calificaciones a través de la Secretaria Académica. Resultados: Se observó una prevalencia de ansiedad estado (AE) y rasgo (AR) de 40.6% y 31.2% respectivamente, ambas con proporciones similares entre nivel medio (75%) y alto (25%), y con asociación entre las mismas. La prevalencia del SB fue de 15.6%, de los cuales 17.2 y 23.4% presentaron niveles altos de cansancio y de despersonalización respectivamente, además 18.8% mostró niveles bajos de realización personal. Conclusión: Al término de la licenciatura los estudiantes muestran sintomatología de AR y AE con alta asociación entre ambas, por lo que es importante resaltar que la ansiedad transitoria puede llegar a integrar una respuesta ansiosa como rasgo de su personalidad. La prevalencia de SB fue baja y sin relación con el rendimiento académico, la edad o el sexo.

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.

Preparation and characterization of epicuticular wax films.

Dipping films from epicuticular wax (EW) were prepared as model systems of epicuticular wax films found in plants. In these films, the growth uniformity, surface morphology, and hydrophobicity were examined. It was observed growth uniformity (linear growth) only from the fifth layer onwards because of the influence of substrate. The surface morphology of the films was found to be composed of pores formed by aggregates of EW molecules, both with a fractal form. An increase in the number of film layers resulted in the increase of the number of pores up to a maximum value followed by a decrease. Such increase was assigned to the growth of aggregates whereas the decrease was explained by the increase of pore sizes, because during the growth of the aggregates, the small pores are replaced by the large pores. Hydrophobicity increased with the number of layers, which was associated with the increase of irregularities on the surface caused by the pores and aggregates. In addition, it was observed that the number of pores increased with temperature. This was explained by the increase in the mobility of EW molecules, which led to a larger amount of EW molecules deposited. Based on our results and the advantages offered by dipping films - including the control of thickness and structure - this type of film is feasible as a model for studies of cuticular water transport in plants.

Mathematical models and fractal analysis for the investigation of the photodynamic inactivation in phytopathogenic microorganisms.

The increasing and indiscriminate use of pesticides may lead to the intoxication and contamination of the environment and foods. In addition, pesticides can cause fungal resistance promoting the selection of resistant phytopathogenic fungi. This is a problem in the agricultural and human health areas, which leads to a need for developing new methodologies to address this problem. Photodynamic inactivation is a promising strategy involving the association of a photosensitizer (PS), light, and molecular oxygen to inhibit the growth of microorganisms. In this work, the PS acridine orange (AO) was deposited using the spray layer-by-layer technique. The effectiveness of the method was evaluated by the analysis of the growth evolution of the colonies as a function of the amount of PS layers applied in field in the presence of sunlight. Image processing and analysis of the fractal theory were used to evaluate the growth of the colonies. The results revealed that AO is a candidate PS for use in field. It was possible to observe the reduction of the growth dynamics of the colonies with the increase of the number of PS layers. The parameters related to the fractality of the system were described by mathematical models of the fractal growth of interfaces. The knowledge of these parameters can help to identify new strategies for the control of phytopathogenic microorganisms that directly affect agricultural production.

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.

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.