Interacciones de materiales y medios con actividad biológica. Impacto sobre células y bacterias

Conferencia del Ciclo "Embajadores" del CENIMLa interfase metal implantable/fluido biológico es muy compleja, ya que interactúan el metal y sus productos de corrosión solubles e insolubles con el medio biológico (que incluye iones, moléculas biológicas, células y/o microorganismos). Dependiendo de la composición y las propiedades fisicoquímicas de la superficie metálica, así como de la composición del medio biológico y de la distancia entre las células y el metal, las interacciones son de distinto tipo. Se analizarán brevemente algunos ejemplos de las interacciones de metales de gran velocidad de degradación como el Mg y otros de menor velocidad de degradación como el Fe y Cu, con células. Asimismo, se mostrarán los resultados obtenidos sobre el control de la degradación que pueden ejercer películas adsorbidas y electropolimerizadas biocompatibles. Por otra parte, se describirán los efectos de la estructura superficial sobre la adherencia y colonización de bacterias, así como el efecto sinérgico sobre la acción de los antibióticosN

Cytotoxicity of Copper Ions Released from Metal : Variation with the Exposure Period and Concentration Gradients

The aim of this work is to contribute to the elucidation of the cytotoxic process caused by the copper ions released from the biomaterials. Clonal cell lines UMR106 were used in the experiments. Copper ions were obtained from two different sources: copper salts and metal dissolution. Experiments carried out with constant ion concentrations (copper salts) were compared with those with concentrations that vary with time and location (dissolution of the metal). Present results and others previously reported could be interpreted through mathematical models that describe: (1) the variation of concentration of copper ions with time and location within a biofilm and (2) the variation of the killing rate with the concentration of the toxic ion and time. The large number of dead cells found near the copper sample with an average ion concentration below the toxic limit could be interpreted bearing in mind that these cells should be exposed to a local concentration higher than this limit. A logarithmic dependence between the number of cells and exposure time was found for nearly constant ion concentrations. Apparent discrepancies, observed when these results and those of different researchers were contrasted, could be explained considering the dissimilar experimental conditions such as the source of the ions and their local concentration at real time.Facultad de Odontologí

Preliminary Characterization of Thin Biofilms by Optical Microscopy

A simple non-invasive technique has been used that employs conventional optical microscopy and a glass flow cell to observe biofilms formed on opaque thin substrata. The technique allows the roughness of the biofilm and the substratum to be evaluated, and the biofilm thickness to be easily measured. The biofilm density may be quantified through colour gradients. In addition, sorne details of biofilm growth processes like the formation of water channels and pores, and interactions between planktonic and sessile cells can be visualized. Results related to the development of thin biofilms and their response to the environment under different conditions are reported. Pure and mixed microbial cultures and different solid substrata were assessed.Facultad de Odontologí

Preliminary Characterization of Thin Biofilms by Optical Microscopy

A simple non-invasive technique has been used that employs conventional optical microscopy and a glass flow cell to observe biofilms formed on opaque thin substrata. The technique allows the roughness of the biofilm and the substratum to be evaluated, and the biofilm thickness to be easily measured. The biofilm density may be quantified through colour gradients. In addition, sorne details of biofilm growth processes like the formation of water channels and pores, and interactions between planktonic and sessile cells can be visualized. Results related to the development of thin biofilms and their response to the environment under different conditions are reported. Pure and mixed microbial cultures and different solid substrata were assessed.Facultad de Odontologí

Microstructural characteristics of thin biofilms through optical and scanning electron microscopy

The combination of a conventional optical microscope with a specially designed glass flow cell was used to visualize ‘in situ’ biofilms formed on opaque thin biomaterials through a simple non-invasive way (optical microscopy of thin biofilms, OMTB). Comparisons of OMTB with scanning electron microscopy (SEM) images were made. Thin metallic dental biomaterials were used as substrata. They were immersed in a synthetic saliva and in a modified Mitis–Salivarius medium inoculated with a consortium of oral microorganisms. To study the effect of bacterial motility, Pseudomonas fluorescens cultures were also used. The processes which give rise to the formation of the biofilm were monitored through OMTB. Biofilm microstructures like pores, water channels, streamers and chains of Streptococci, attached to the surface or floating in the viscous interfacial environment, could be distinguished. Thickness and roughness of the biofilms formed on thin substrata could also be evaluated. Distortions introduced by pretreatments carried out to prepare biological materials for SEM observations could be detected by comparing OMTB and SEM images. SEM images (obtained at high magnification but ex situ, not in real time and with pretreatment of the samples) and OMTB images (obtained in situ, without pretreatments, in real time but at low magnification) in combination provided complementary information to study biofilm processes on thin substrata.Facultad de Odontologí

Microstructural characteristics of thin biofilms through optical and scanning electron microscopy

The combination of a conventional optical microscope with a specially designed glass flow cell was used to visualize ‘in situ’ biofilms formed on opaque thin biomaterials through a simple non-invasive way (optical microscopy of thin biofilms, OMTB). Comparisons of OMTB with scanning electron microscopy (SEM) images were made. Thin metallic dental biomaterials were used as substrata. They were immersed in a synthetic saliva and in a modified Mitis–Salivarius medium inoculated with a consortium of oral microorganisms. To study the effect of bacterial motility, Pseudomonas fluorescens cultures were also used. The processes which give rise to the formation of the biofilm were monitored through OMTB. Biofilm microstructures like pores, water channels, streamers and chains of Streptococci, attached to the surface or floating in the viscous interfacial environment, could be distinguished. Thickness and roughness of the biofilms formed on thin substrata could also be evaluated. Distortions introduced by pretreatments carried out to prepare biological materials for SEM observations could be detected by comparing OMTB and SEM images. SEM images (obtained at high magnification but ex situ, not in real time and with pretreatment of the samples) and OMTB images (obtained in situ, without pretreatments, in real time but at low magnification) in combination provided complementary information to study biofilm processes on thin substrata.Facultad de Odontologí

Cytotoxicity of Copper Ions Released from Metal : Variation with the Exposure Period and Concentration Gradients

The aim of this work is to contribute to the elucidation of the cytotoxic process caused by the copper ions released from the biomaterials. Clonal cell lines UMR106 were used in the experiments. Copper ions were obtained from two different sources: copper salts and metal dissolution. Experiments carried out with constant ion concentrations (copper salts) were compared with those with concentrations that vary with time and location (dissolution of the metal). Present results and others previously reported could be interpreted through mathematical models that describe: (1) the variation of concentration of copper ions with time and location within a biofilm and (2) the variation of the killing rate with the concentration of the toxic ion and time. The large number of dead cells found near the copper sample with an average ion concentration below the toxic limit could be interpreted bearing in mind that these cells should be exposed to a local concentration higher than this limit. A logarithmic dependence between the number of cells and exposure time was found for nearly constant ion concentrations. Apparent discrepancies, observed when these results and those of different researchers were contrasted, could be explained considering the dissimilar experimental conditions such as the source of the ions and their local concentration at real time.Facultad de Odontologí

EFECTO DE LA LUZ UV EN NANOTUBOS DE CARBONO MULTICAPA COMERCIALES

Junto con la síntesis de nanotubos de carbono, que hoy en día se utilizan para numerosas aplicaciones debido a sus propiedades que los hacen especiales (alta conductividad eléctrica, resistencia térmica y mecanica, etc), se producen nanopartículas de metales de distinta naturaleza, provenientes de los catalizadores metálicos que se utilizan para sintetizarlos y productos secundarios como por ejemplo, carbono amorfo. Con el fin de investigar el rol de estos residuos secundarios en los procesos fotoquímicos que ocurren luego de irradiar las muestra de nanotubos comerciales con luz UV (350-355 nm), se determinó la generación de especies reactivas del oxígeno y se observaron variaciones en la morfología de los nanomateriales pristinos. Para ello, se utilizaron técnicas como HRTEM, XPS, Raman,TGA, Espectroscopia de resonancia paramagnetica y de absorción de transcientes. Los resultados indican que la fotólisis de los nanotubos con luz UV conlleva a la oxidación superficial de los nanotubos, en los lugares donde hay mayores defectos superficiales como grupos funcionales de carbono oxidado. La pérdida de las capas más oxidadas causan que el nanotubo adquiera una naturaleza más grafítica. Tanto los residuos metálicos, el carbono amorfo con alto contenido en oxígeno y los defectos superficiales de carbono oxidado del nanotubo, juegan un rol muy importante en la generación de estados con separación de cargas fotoinducidas dentro del nanotubo. Los resultados indican que la excitación a 350 nm de los nanotubos comerciales conduce a la formación de un excitón, seguido de una transferencia del hueco  a los óxidos metálicos , quedando el electrón en el nanotubo. El mecanismo que se plantea explica la ruptura de los NTC en las zonas de los defectos, dejando expuestas las paredes internas menos oxidadas (NTC mas grafíticos), la eliminación de estructuras de tipo oxido de grafeno con dimensiones nanoscópicas y la oxidación de los residuos metálicos. Al presente se investiga la capacidad oxidante de los residuos de grafeno

Una aproximación al léxico disponible de futuros profesores portugueses de ELE en dominios pedagógico-didácticos

ES: Pese al auge experimentado en los últimos años por los estudios de disponibilidad léxica, aún son escasas las investigaciones sobre el léxico específico de comunidades científicas y/o profesionales (Quintanilla y Salcedo, 2019), una constatación extensible al ámbito de la formación inicial de profesores de lenguas extranjeras. Con este trabajo, siguiendo la metodología propia de la disponibilidad léxica, pretendemos contribuir a ampliar la nómina de investigaciones dedicadas al análisis del léxico disponible de profesores de español como lengua extranjera (ELE) en procesos de formación inicial. Para ello, hemos aplicado pruebas psicolingüísticas a 11 informantes que durante el año lectivo 2021-2022 estaban estudiando el primer o el segundo curso de los dos másteres profesionalizantes en la enseñanza de español ofertados por la Faculdade de Letras de la Universidade do Porto, con miras a obtener datos sobre cinco dominios pedagógico-didácticos: planificación de clase, gestión de clase, evaluación, TIC y cultura hispánica. Los resultados indican que los centros de interés en los que los informantes han activado más vocabulario son "planificación de clase" y "evaluación". Por otra parte, el promedio de palabras por informante es superior en el grupo constituido por los informantes de primer curso, mientras que el índice de cohesión es superior en el grupo de informantes de segundo curso.Despite the boom experienced in recent years by lexical availability studies, research on the specific lexicon of scientific and/or professional communities is still scarce (Quintanilla and Salcedo, 2019), a finding that can be extended to the field of initial teacher training of foreign languages. With this work, following the methodology of lexical availability, we aim to contribute to expanding the list of research dedicated to the analysis of the lexicon available to Spanish as a foreign language (SFL) in initial teacher training processes. For this, we have applied psycholinguistic tests to 11 informants who, during the academic year 2021-2022, were studying the first or second year of the two professional master's degrees in Spanish teaching offered by the Faculty of Arts and Humanities of the University of Porto, in order to obtain data on five pedagogical-didactic prompts: lesson planning, classroom management, assessment, ICT and Hispanic culture. The results indicate that the prompts in which the informants have activated more vocabulary are "lesson planning" and "assessment". On the other hand, the average number of words per informant is higher in the group made up of first-year informants, while the cohesion index is higher in the group of second-year informants

Cellular response to rare earth mixtures (La and Gd) as components of degradable Mg alloys for medical applications

Rare earth (RE) elements have been proposed to improve the corrosion resistance of degradable Mg alloys for medical applications. However, good biocompatibility of the elements released by Mg alloys during degradation is essential for their use in implants. Most studies are focused on material science and engineering aspects, but the effects of ions released at the biological interface are not frequently addressed. The aim of this study was to contribute to the knowledge of in vitro toxicological effects of two RE Mg-alloying elements, La and Gd, as individual ions and in mixtures with and without Mg ions. Different combinations (Mg + Gd, Mg + La, and Mg + Gd + La) were used to evaluate their possible synergistic effects on CHO-K1 cells. Two sets of experiments were designed to assess (1) the cyto-genotoxic effect of La and Gd ions by neutral red (NR) technique, Reduction of tetrazolium salt (MTT), Viability with Acridine Orange staining, Clonogenic test, and Comet assay; and, (2) the possible synergistic toxicological effect of La and Gd ions in mixtures, and the influence of osmolarity increase on cellular response. Cytotoxic effects of RE were found at concentrations ≥200 μM RE while DNA damage was detected for doses ≥1500 μM and ≥1600 μM for La and Gd, respectively. When mixtures of ions were evaluated, neither synergistic cytotoxic effects nor biological damage related to osmolarity increase were detected.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada