Selective enhancement of individual cantilever high resonance modes.

Multifrequency atomic force microscopy (AFM) in liquid media where several eigenmodes or harmonics are simultaneously excited is improving the performance of the scanning probe techniques in biological studies. As a consequence, an important effort is being made to search for a reliable, efficient and strong cantilever high mode excitation method that operates in liquids. In this work we present (theoretical and experimentally) a technique for improving the efficiency of the most common excitation methods currently used in AFM operated in liquids: photothermal, torque (MAC Mode™) and magnetostriction. By etching specific areas of the cantilever coating, the oscillation amplitude (both flexural and torsional) of each specific eigenmode increases, leading to an improvement in signal to noise ratio of the multifrequency techniques. As an alternative, increment in high mode oscillation amplitude is also obtained by Ga(+) ion implantation in the specific areas of the magnetic material.

Nanoparticle-mediated monitoring of carbohydrate-lectin interactions using Transient Magnetic Birefringence.

The development of sensitive and easy-to-use biosensors that allow an adequate characterization of specific weak biological interactions like carbohydrate-lectin interactions still remains challenging today. Nanoparticles functionalized with carbohydrates are one of the most powerful systems for studying carbohydrate-lectin interactions, because they mimic the multivalent presentation of carbohydrates encountered in nature, for example when viruses and bacteria bind to cells. On the basis of the model system glucose-Concanavalin A (ConA), we explore the application of Transient Magnetic Birefringence (TMB) to study these weak interactions, using glucose-functionalized colloidal magnetite nanoparticles (NPs) as probes. We demonstrate that the binding dynamics can be monitored and derive a model to obtain the apparent cooperativity. For our studies, we use nanoparticles of 6 and 8 nm in diameter. The ConA-generated response shows apparent cooperativity, due to the cross-linking of nanoparticles by the ConA tetramer which has four binding sites. Cooperativity is higher for 6 nm NPs, possibly due to a better accessibility of all four ConA binding sites on smaller NPs, enhancing cross-linking. For this system, we find a detection limit of 3-23 nM.

Transient magnetic birefringence for determining magnetic nanoparticle diameters in dense, highly light scattering media.

The increasing use of biofunctionalized magnetic nanoparticles in biomedical applications calls for further development of characterization tools that allow for determining the interactions of the nanoparticles with the biological medium in situ. In cell-incubating conditions, for example, nanoparticles may aggregate and serum proteins adsorb on the particles, altering the nanoparticles' performance and their interaction with cell membranes. In this work we show that the aggregation of spherical magnetite nanoparticles can be detected with high sensitivity in dense, highly light scattering media by making use of magnetically induced birefringence. Moreover, the hydrodynamic particle diameter distribution of anisometric nanoparticle aggregates can be determined directly in these media by monitoring the relaxation time of the magnetically induced birefringence. As a proof of concept, we performed measurements on nanoparticles included in an agarose gel, which scatters light in a similar way as a more complex biological medium but where particle-matrix interactions are weak. Magnetite nanoparticles were separated by agarose gel electrophoresis and the hydrodynamic diameter distribution was determined in situ. For the different particle functionalizations and agarose concentrations tested, we could show that gel electrophoresis did not yield a complete separation of monomers and small aggregates, and that the electrophoretic mobility of the aggregates decreased linearly with the hydrodynamic diameter. Furthermore, the rotational particle diffusion was not clearly affected by nanoparticle-gel interactions. The possibility to detect nanoparticle aggregates and their hydrodynamic diameters in complex scattering media like cell tissue makes transient magnetic birefringence an interesting technique for biological applications.

Effect of intravenous hydralazine infusion on maternal plasma nitric oxide levels in gestations complicated with severe preeclampsia: a pilot study.

AIM: To investigate the effect of intravenous hydralazine infusion on maternal nitric oxide (NO) levels. METHODS: This pilot study comprised 40 (n = 40) gestations complicated with severe preeclampsia to whom maternal plasma NO levels were determined by chemiluminescence before and after hydralazine administration. Blood pressure values were concomitantly assessed. RESULTS: After 20 min of intravenous hydralazine infusion blood pressure values decrease significantly in term and preterm gestations. This was accompanied by an overall significant decrease in mean plasma NO values (38.7 ± 12.9 to 35.4 ± 13.9 µmol/L, p < 0.05). Despite this, NO values decreased in 67.5% of cases (a 17.6% from baseline) and increased in 32.5% (a 14.8% from baseline) (p < 0.05 for both). Blood pressure decrease (%) was lower (systolic and diastolic) among those displaying a NO decrement than in the increment group. Interestingly, gestational age was higher in the group displaying decreased NO; however, this did not reach statistical significance (37.5 ± 2.7 vs. 35.9 ± 2.8 weeks, p = 0.08). CONCLUSION: The results of this study fail to demonstrate a similar NO secretion after hydralazine infusion in women with severe preeclampsia.

Nanogeometry matters: unexpected decrease of capillary adhesion forces with increasing relative humidity.

The sticking effect between hydrophilic surfaces occurring at increasing relative humidity (RH) is an everyday phenomenon with uncountable implications. Here experimental evidence is presented for a counterintuitive monotonous decrease of the capillary adhesion forces between hydrophilic surfaces with increasing RH for the whole humidity range. It is shown that this unexpected result is related to the actual shape of the asperity at the nanometer scale: a model based on macroscopic thermodynamics predicts this decrease in the adhesion force for a sharp object ending in an almost flat nanometer-sized apex, in full agreement with experiments. This anomalous decrease is due to the fact that a significant growth of the liquid meniscus formed at the contact region with increasing humidity is hindered for this geometry. These results are relevant in the analysis of the dynamical behavior of nanomenisci. They could also have an outstanding value in technological applications, since the undesirable sticking effect between surfaces occurring at increasing RH could be avoided by controlling the shape of the surface asperities at the nanometric scale.

Carbohydrate-carbohydrate interaction prominence in 3D supramolecular self-assembly.

Self-association in water of biologically significant carbohydrate molecules is a controversial topic due to the strong solvation of these molecules in this solvent and the difficulty to experimentally detect these very weak intermolecular forces by biophysical techniques. Herein we report the tremendous ability of amphiphilic carbohydrate molecules to form complex three-dimensional architectures. We have experimentally observed the 3D self-assembly into multilayers of disaccharide neoglycolipid dimers on graphite by means of noncontact AFM and we have also theoretically modeled the interaction between two dimers in order to learn about the structure and composition of these layers. A simple bilayer structure as observed for many amphiphilic lipids was discarded by the experiments. Instead, based on the good agreement between experiments and calculations, we propose that multilayer formation takes place through the assembly of building blocks consisting of two dimers each. The fundamental key in the formation of this supramolecular structure is the complementarity between the van der Waals surfaces of the amphiphilic carbohydrate molecules, a result which differs from the most common idea that H-bonding interactions are prominent in carbohydrate-mediated interactions.

Biopelícula cariogénica de Streptococcus mutans y efecto hemostático de ácido tánico en la hemorragia post-exodoncia / Streptococcus mutans cariogenic biofilm and hemostatic effect of tannic acid in post-extraction hemorrhage

La caries dental y la placa dental se encuentran entre las enfermedades más comunes en todo el mundo y son causadas por una mezcla de microorganismos y restos de alimentos. Tipos específicos de bacterias productoras de ácido, especialmente Streptococcus mutans, colonizan la superficie dental y causan daño a la estructura dental dura en presencia de carbohidratos fermentables, por ejemplo, sacarosa y fructosa. Por otro lado, el sangrado posterior a la extracción es una complicación reconocida y frecuente en la práctica dental, que se define como la pérdida de sangre que continúa más allá de las 8 a 12 horas después de la exodoncia. Existe una amplia gama de técnicas sugeridas y sustancias para el tratamiento del sangrado post-extracción, que incluyen intervenciones dirigidas tanto a causas locales como sistémicas. El ácido tánico es una de las sustancias astringente que precipitan proteínas, pero no penetran en las células, por lo que inciden solo en la capa superficial. Su objetivo se enfoca a robustecer la superficie para acrecentar su resistencia mecánica y reducir la exudación. El objetivo de este estudio fue determinar la presencia de S. mutans en las biopelículas dentales y al mismo tiempo evaluar la actividad del ácido tánico como inhibidor del sangrado profuso en las extracciones dentales. S. mutans se aisló en el 92,5% de los pacientes evaluados. Los tiempos de hemostasia post-exodoncia fue significativamente menor en el grupo de pacientes a los que se les aplicó el ácido tánico en comparación a los que no se les aplicó(AU)

Tooth decay and dental plaque are among the most common diseases worldwide and are caused by a mix of microorganisms and food debris. Specific types of acid-producing bacteria, especially Streptococcus mutans, colonize the tooth surface and cause damage to hard tooth structure in the presence of fermentable carbohydrates, for example, sucrose and fructose. On the other hand, post-extraction bleeding is a recognized and frequent complication in dental practice, defined as blood loss that continues beyond 8 to 12 hours after extraction. There is a wide range of suggested techniques and substances for the treatment of post-extraction bleeding, including interventions targeting both local and systemic causes. Tannic acid is one of the astringent substances that precipitate proteins, but does not penetrate the cells, so it affects only the superficial layer. Its objective is focused on strengthening the surface to increase its mechanical resistance and reduce exudation. The objective of this study was to determine the presence of S. mutans in dental biofilms and at the same time to evaluate the activity of tannic acid as an inhibitor of profuse bleeding in dental extractions. S. mutans was isolated in 92.5% of the patients evaluated. Post-extraction hemostasis times were significantly shorter in the group of patients who received tannic acid compared to those who did not(AU)

Efecto antimicrobiano de la irrigación postquirúrgica con agua ozonificada en el alveolo durante exodoncias simples / Antimicrobial effect of postsurgical irrigation with ozonated water in the socket during simple extractions

El presente estudio se propone evaluar los efectos postquirúrgicos de la irrigación del alveolo con agua ozonificada durante una exodoncia simple en pacientes de la Unidad de Atención Odontológica UNIANDES. Para ello se seleccionaron 30 pacientes a los que se les practicaron dos exodoncias en sesiones diferentes aplicándose agua ozonificada post exodoncia solamente en la primera de ellas, lo que permitió comparar en cada alternativa el comportamiento de la intensidad del dolor, grado de inflamación, infección, y tiempo de cicatrización, de manera que las pruebas estadísticas fueron significativas mostrando asociación lineal entre las variables irrigación del alveolo y dolor; y entre la irrigación del alveolo e inflamación. Asimismo, se observó una cicatrización más rápida en los pacientes tratados con el agua ozonificad en comparación a aquellos que no fueron tratados. Además, ese observó una disminución de la biota bucal, especialmente Lactobacillus spp y Streptococcus mutans al irrigar con agua ozonificada responsable de la inflamación y por ende del dolor de los pacientes. Por otra parte, se aprecia un escaso conocimiento acerca de la utilización de agua ozonificada en el alvéolo por parte de los estudiantes, mientras que los profesionales odontólogos, y a pesar de tener conocimiento de los beneficios del agua azonificada, son poco proclives a su uso(AU)

The present study aims to evaluate the post-surgical effects of alveolar irrigation with ozonated water during a simple extraction in patients of the UNIANDES Dental Care Unit. For this, 30 patients were selected who underwent two extractions in different sessions, applying post-extraction ozonated water only in the first one, which allowed comparing in each alternative the behavior of pain intensity, degree of inflammation, infection, and healing time, so that the statistical tests were significant, showing a linear association between the variables irrigation of the socket and pain; and between alveolar blood supply and inflammation. Likewise, faster healing was observed in patients treated with ozonated water compared to those who were not treated. In addition, he observed a decrease in the oral biota, especially Lactobacillus spp and Streptococcus mutans when irrigating with ozonated water, responsible for the inflammation and therefore the pain of the patients. On the other hand, there is little knowledge about the use of ozonated water in the alveolus by students, while dental professionals, despite being aware of the benefits of zonated water, are not inclined to use it(AU)

El conocimiento del Kichwa, segunda lengua oficial del Ecuador ¿compromete la comunicación médico/odontólogo-paciente? / Knowledge of the Kichwa, second official language of Ecuador, compromises the dentist/medical-patient communication?

Con el propósito de analizar el comportamiento de las relaciones entre médico/odontólogo y paciente, mediadas por la comunicación intercultural, se realizó un estudio que contó con la participación de 200 indígenas de la etnia Kichwa Salasaka y 33 profesionales sanitarios. Mediante la aplicación de encuestas fueron explorados elementos esenciales como los idiomas que ambos grupos dominan; asistencia a consulta de los indígenas; calidad de la atención; formación bilingüe del odontólogo y percepción de la comprensión por parte de ambos grupos. Entre los resultados obtenidos se encuentra la no comprensión de los pacientes de las orientaciones que reciben en la consulta, insuficiente conocimiento la lengua Kichwa por parte del equipo de salud y en consecuencia insuficiente transferencia de la información. Identificada la problemática comunicacional médico/odontólogo - paciente, se recomienda la implementación de políticas de salud sustentadas en el enfoque intercultural(AU)

With the purpose of analyzing the behavior of the medical/dentist-patient relations, mediated by the intercultural communication, a study was carried out that counted on the participation of 70 indigenous people of the ethnic Kichwa Salasaca and 33 doctors and dentist. Through the application of surveys, essential elements were explored such as the languages that both groups dominate; assistance to indigenous consultation; Quality of care; Bilingual training of the dentist and perception of the understanding on the part of both groups. Among the results obtained is the non-comprehension of the patients of the orientations they receive in the consultation, insufficient knowledge the Kichwa language by the health team and consequently insufficient transfer of the information. Identified the communicational problems medical/entist-patient, we recommend the implementation of health policies based on the intercultural approach(AU)

[Lung transplantation for emphysema: retrospective study of 65 patients]. / Trasplante pulmonar por enfisema: análisis retrospectivo de 65 pacientes.

BACKGROUND AND OBJECTIVE: Our goal was to analyze the incidence of perioperative complications in patients with pulmonary emphysema who underwent lung transplantation and to identify variables associated with the incidence of morbidity and mortality during the immediate postoperative period. PATIENTS AND METHOD: We undertook a retrospective study of 65 pulmonary emphysema patients who received lung transplants from 1994 through 2002 with the aim of determining the most common intra- and early postoperative complications in the ICU. An univariate analysis was carried out in order to identify variables associated with the incidence of mortality and postoperative complications. Those variables showing statistical significance underwent a multivariate analysis, by means of a pattern of logistic regression, in order to calculate the odds ratio and confidence interval. RESULTS: Seventeen patients received single-lung transplants (SLT) and 48 patients received sequential double-lung transplants (DLT). Intraoperative complications appeared more frequently in the DLT group. Most frequent complications during surgery were reperfusion syndrome (44.6%) and pulmonary hypertension (16.9%). The intraoperative survival was 100%. Fifty-five patients had some type of postoperative complication. Commonest postoperative complications were infection (56.9%) and primary graft failure (36.6%). In the early postoperative period the mortality rate was 16.9%. Main cause of death in the ICU was sepsis (54.5%). A time of mechanical ventilation > 48 hours and postoperative hemorrhage were the variables with a higher predictive value for mortality in the early postoperative period. CONCLUSIONS: Patients with SLT had a lower rate of perioperative complications and a higher survival during their stay in the ICU. Time of mechanical ventilation > 48 hours and postoperative hemorrhage were the variables that best predicted death in the early postoperative period following lung transplantation. Despite our experience, however, perioperative mortality in lung transplantation remains high up to this day.

Parallel nanogap fabrication with nanometer size control using III-V semiconductor epitaxial technology.

A nanogap fabrication process using strained epitaxial III-V beams is reported. The process is highly reproducible, allowing parallel fabrication and nanogap size control. The beams are fabricated from MBE-grown (GaAs/GaP)/AlGaAs strained heterostructures, standard e-beam lithography and wet etching. During the wet etching process, the relaxation of the accumulated stress at the epitaxial heterostructure produces a controlled beam breakage at the previously defined beam notch. After the breakage, the relaxed strain is proportional to the beam length, allowing nanogap size control. The starting structure is similar to a mechanically adjustable break junction but the stress causing the breakage is, in this case, built into the beam. This novel technique should be useful for molecular-scale electronic devices.

Supramolecular self-assembled arrangements of maltose glyconanoparticles.

Our group previously reported the preparation of water-soluble Au-Fe(x)O(y) nanoparticles functionalized with a maltose neoglycoconjugate. A fraction soluble in methanol was also separated and originated a new supramolecular polymeric aggregate. We report here the full characterization of this novel material by transmission electron microscopy (TEM), fluorescence emission, and atomic force microscopy. By means of noncontact dynamic atomic force microscopy, we have been able to obtain information about the organization of the organic components of the polymers, which eluded TEM analysis. We have observed that polymers packed in units about 65 nm in length and 40 nm in width on Au surfaces. The nanoparticles seem to be encapsulated by the organic material. We propose interactions between the sugar residues and the amphiphilic character of the maltose neoglycoconjugate (with a lipophilic undecane spacer) as responsible for the origin of these amazing supramolecular arrangements.