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

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

La rugosidad y composición de las salivaderas y la formación del biofilm

Objetivo: Relacionar la incidencia que tiene la rugosidad y composición superficial de las caras internas de las salivaderas dentales en la formación del biofilm. Materiales y métodos: Se realizaron 10 cortes de las paredes internas cercanas al desagüe de tres salivaderas dentales en desuso de opalina, cerámica y acero inoxidable. Se analizó la rugosidad superficial de cada uno de los cortes con un rugosímetro Hommel Tester 1000.Facultad de Odontologí

The electrooxidation of glucose on platinum electrodes in buffered media

Kinetic studies of glucose electrooxidation are of special interest in fundamental and applied electrochemistry. The electrochemical reaction on bright Pt electrodes is investigated through the application of combined potential/time perturbation programs and electrolytes of different compositions at temperatures ranging from 30 to 64°C. The electrooxidation of glucose should occur through the formation of several intermediate species and the overall reaction pathway should consist of different stage considering electroadsorption, chemical and electrochemical processes. The influence of potential perturbation conditions, anion adsorption, inhibition reactions of products and temperature are analysed through changes in U/I profiles.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

La rugosidad y composición de las salivaderas y la formación del biofilm

Objetivo: Relacionar la incidencia que tiene la rugosidad y composición superficial de las caras internas de las salivaderas dentales en la formación del biofilm. Materiales y métodos: Se realizaron 10 cortes de las paredes internas cercanas al desagüe de tres salivaderas dentales en desuso de opalina, cerámica y acero inoxidable. Se analizó la rugosidad superficial de cada uno de los cortes con un rugosímetro Hommel Tester 1000.Facultad de Odontologí