Glyoxal crosslinking of electro-responsive alginate-based hydrogels: Effects on the properties.

To improve the features of alginate-based hydrogels in physiological conditions, Ca2+-crosslinked semi-interpenetrated hydrogels formed by poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid and alginate (PEDOT/Alg) were subjected to a treatment with glyoxal to form a dual ionic/covalent network. The covalent network density was systematically varied by considering different glyoxalization times (tG). The content of Ca2+ was significantly higher for the untreated hydrogel than for the glyoxalized ones, while the properties of the hydrogels were found to largely depend on tG. The porosity and swelling capacity decreased with increasing tG, while the stiffness and electrical conductance retention capacity increased with tG. The potentiodynamic response of the hydrogels notably depended on the amount of conformational restraints introduced by the glyoxal, which is a very short crosslinker. Thus, the re-accommodation of the polymer chains during the cyclic potential scans became more difficult with increasing number of covalent crosslinks. This information was used to improve the performance of untreated PEDOT/Alg as electrochemical sensor of hydrogen peroxide by simply applying a tG of 5 min. Overall, the control of the properties of glyoxalized hydrogels through tG is very advantageous and can be used as an on-demand strategy to improve the performance of such materials depending on the application.

Enzymatic Degradation of Polylactic Acid Fibers Supported on a Hydrogel for Sustained Release of Lactate.

The incorporation of exogenous lactate into cardiac tissues is a regenerative strategy that is rapidly gaining attention. In this work, two polymeric platforms were designed to achieve a sustained release of lactate, combining immediate and prolonged release profiles. Both platforms contained electrospun poly(lactic acid) (PLA) fibers and an alginate (Alg) hydrogel. In the first platform, named L/K(x)/Alg-PLA, lactate and proteinase K (x mg of enzyme per 1 g of PLA) were directly loaded into the Alg hydrogel, into which PLA fibers were assembled. In the second platform, L/Alg-K(x)/PLA, fibers were produced by electrospinning a proteinase K:PLA solution and, subsequently, assembled within the lactate-loaded hydrogel. After characterizing the chemical, morphological, and mechanical properties of the systems, as well as their cytotoxicity, the release profiles of the two platforms were determined considering different amounts of proteinase K (x = 5.2, 26, and 52 mg of proteinase K per 1 g of PLA), which is known to exhibit a broad cleavage activity. The profiles obtained using L/Alg-K(x)/PLA platforms with x = 26 and 52 were the closest to the criteria that must be met for cardiac tissue regeneration. Finally, the amount of lactate directly loaded in the Alg hydrogel for immediate release and the amount of protein in the electrospinning solution were adapted to achieve a constant lactate release of around 6 mM per day over 1 or 2 weeks. In the optimized bioplatform, in which 6 mM lactate was loaded in the hydrogel, the amount of fibers was increased by a factor of ×3, the amount of enzyme was adjusted to 40 mg per 1 g of PLA, and a daily lactate release of 5.9 ± 2.7 mM over a period of 11 days was achieved. Accordingly, the engineered device fully satisfied the characteristics and requirements for heart tissue regeneration.

Immediate-sustained lactate release using alginate hydrogel assembled to proteinase K/polymer electrospun fibers.

This work proposes a microfibers-hydrogel assembled composite as delivery vehicle able to combine into a single system both burst and prolonged release of lactate. The prolonged release of lactate has been achieved by electrospinning a mixture of polylactic acid and proteinase K (26.0 mg of proteinase K and 0.99 g of PLA dissolved in 6 mL of 2:1 chloroform:acetone in the optimal case), which is a protease that catalyzes the degradation of polylactic acid into lactate. The degradation of microfibers into lactate reflects that proteinase K preserves its enzymatic activity even after the electrospinning process because of the mild operational conditions used. Besides, burst release is obtained from the lactate-loaded alginate hydrogel. The successful assembly between the lactate-loaded hydrogel and the polylactic acid/proteinase K fibers has been favored by applying a low-pressure (0.3 mbar at 300 W) oxygen plasma treatment, which transforms hydrophobic fibers into hydrophilic while the enzymatic activity is still maintained. The composite displays both fast (< 24 h) and sustained (> 10 days) lactate release, and allows the modulation of the release by adjusting either the amount of loaded lactate or the amount of active enzyme.

Unveiling the Rolling to Kayak Transition in Propelling Nanorods with Cargo Trapping and Pumping.

Magnetic nanorods driven by rotating fields in water can be rapidly steered along any direction while generating strong and localized hydrodynamic flow fields. Here we show that, when raising the frequency of the rotating field, these nanopropellers undergo a dynamic transition from a rolling to a kayak-like motion due to the increase in viscous drag and acquire a finite inclination angle with respect to the plane perpendicular to the bottom surface. We explain these experimental observations with a theoretical model which considers the nanorod as a pair of ferromagnetic particles hydrodynamically interacting with a close stationary surface. Further, we quantify how efficiently microscopic cargoes can be trapped or expelled from the moving nanorod and use numerical simulations to unveil the generated hydrodynamic flow field. These propulsion regimes can be implemented in microfluidic devices to perform precise operations based on the selective sorting of microscopic cargoes.

Multitasking smart hydrogels based on the combination of alginate and poly(3,4-ethylenedioxythiophene) properties: A review.

Poly(3,4-ethylenedioxythiophene) (PEDOT), a very stable and biocompatible conducting polymer, and alginate (Alg), a natural water-soluble polysaccharide mainly found in the cell wall of various species of brown algae, exhibit very different but at the same complementary properties. In the last few years, the remarkable capacity of Alg to form hydrogels and the electro-responsive properties of PEDOT have been combined to form not only layered composites (PEDOT-Alg) but also interpenetrated multi-responsive PEDOT/Alg hydrogels. These materials have been found to display outstanding properties, such as electrical conductivity, piezoelectricity, biocompatibility, self-healing and re-usability properties, pH and thermoelectric responsiveness, among others. Consequently, a wide number of applications are being proposed for PEDOT-Alg composites and, especially, PEDOT/Alg hydrogels, which should be considered as a new kind of hybrid material because of the very different chemical nature of the two polymeric components. This review summarizes the applications of PEDOT-Alg and PEDOT/Alg in tissue interfaces and regeneration, drug delivery, sensors, microfluidics, energy storage and evaporators for desalination. Special attention has been given to the discussion of multi-tasking applications, while the new challenges to be tackled based on aspects not yet considered in either of the two polymers have also been highlighted.

Hybrid conducting alginate-based hydrogel for hydrogen peroxide detection from enzymatic oxidation of lactate.

A conducting nanocomposite hydrogel is developed for the detection of L-lactate. The hydrogel is based on a mixture of alginate (Alg) and poly(3,4-ethylenedioxythiophene) (PEDOT), which is loaded with gold nanoparticles (GNP). In this novel hydrogel, Alg provides 3D structural support and flexibility, PEDOT confers conductivity and sensing capacity, and GNP provides signal amplification with respect to simple voltammetric and chronoamperometric response. The synergistic combination of the properties provided by each component results in a new flexible nanocomposite with outstanding capacity to detect hydrogen peroxide, which has been used to detect the oxidation of L-lactate. The hydrogel detects hydrogen peroxide with linear response and limits of detection of 0.91 µM and 0.02 µM by cyclic voltammetry and chronoamperometry, respectively. The hydrogel is functionalized with lactate oxidase, which catalyzes the oxidation of L-lactate to pyruvate, forming hydrogen peroxide. For L-lactate detection, the functionalized biosensor works in two linear regimes, one for concentrations lower than 5 mM with a limit of detection of 0.4 mM, and the other for concentrations up to 100 mM with a limit of detection of 3.5 mM. Because of its linear range interval, the developed biosensor could be suitable for a wide number of biological fluids.

Remote Spatiotemporal Control of a Magnetic and Electroconductive Hydrogel Network via Magnetic Fields for Soft Electronic Applications.

Multifunctional hydrogels are a class of materials offering new opportunities for interfacing living organisms with machines due to their mechanical compliance, biocompatibility, and capacity to be triggered by external stimuli. Here, we report a dual magnetic- and electric-stimuli-responsive hydrogel with the capacity to be disassembled and reassembled up to three times through reversible cross-links. This allows its use as an electronic device (e.g., temperature sensor) in the cross-linked state and spatiotemporal control through narrow channels in the disassembled state via the application of magnetic fields, followed by reassembly. The hydrogel consists of an interpenetrated polymer network of alginate (Alg) and poly(3,4-ethylenedioxythiophene) (PEDOT), which imparts mechanical and electrical properties, respectively. In addition, the incorporation of magnetite nanoparticles (Fe3O4 NPs) endows the hydrogel with magnetic properties. After structural, (electro)chemical, and physical characterization, we successfully performed dynamic and continuous transport of the hydrogel through disassembly, transporting the polymer-Fe3O4 NP aggregates toward a target using magnetic fields and its final reassembly to recover the multifunctional hydrogel in the cross-linked state. We also successfully tested the PEDOT/Alg/Fe3O4 NP hydrogel for temperature sensing and magnetic hyperthermia after various disassembly/re-cross-linking cycles. The present methodology can pave the way to a new generation of soft electronic devices with the capacity to be remotely transported.

Propulsion and energetics of a minimal magnetic microswimmer.

In this manuscript we describe the realization of a minimal hybrid microswimmer, composed of a ferromagnetic nanorod and a paramagnetic microsphere. The unbounded pair is propelled in water upon application of a swinging magnetic field that induces a periodic relative movement of the two composing elements, where the nanorod rotates and slides on the surface of the paramagnetic sphere. When taken together, the processes of rotation and sliding describe a finite area in the parameter space, which increases with the frequency of the applied field. We develop a theoretical approach and combine it with numerical simulations, which allow us to understand the dynamics of the propeller and explain the experimental observations. Furthermore, we demonstrate a reversal of the microswimmer velocity by varying the length of the nanorod, as predicted by the model. Finally, we determine theoretically and in experiments the Lighthill's energetic efficiency of this minimal magnetic microswimmer.

Electroresponsive Alginate-Based Hydrogels for Controlled Release of Hydrophobic Drugs.

Stimuli-responsive biomaterials have attracted significant attention for the construction of on-demand drug release systems. The possibility of using external stimulation to trigger drug release is particularly enticing for hydrophobic compounds, which are not easily released by simple diffusion. In this work, an electrochemically active hydrogel, which has been prepared by gelling a mixture of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and alginate (Alg), has been loaded with curcumin (CUR), a hydrophobic drug with a wide spectrum of clinical applications. The PEDOT/Alg hydrogel is electrochemically active and organizes as segregated PEDOT- and Alg-rich domains, explaining its behavior as an electroresponsive drug delivery system. When loaded with CUR, the hydrogel demonstrates a controlled drug release upon application of a negative electrical voltage. Comparison with the release profiles obtained applying a positive voltage and in the absence of electrical stimuli indicates that the release mechanism dominating this system is complex because of not only the intermolecular interactions between the drug and the polymeric network but also the loading of a hydrophobic drug in a water-containing delivery system.

Direct measurement of Lighthill's energetic efficiency of a minimal magnetic microswimmer.

The realization of artificial microscopic swimmers able to propel in viscous fluids is an emergent research field of fundamental interest and vast technological applications. For certain functionalities, the efficiency of the microswimmer in converting the input power provided through an external actuation into propulsive power output can be critical. Here we use a microswimmer composed by a self-assembled ferromagnetic rod and a paramagnetic sphere and directly determine its swimming efficiency when it is actuated by a swinging magnetic field. Using fast video recording and numerical simulations we fully characterize the dynamics of the propeller and identify the two independent degrees of freedom which allow its propulsion. We then obtain experimentally the Lighthill's energetic efficiency of the swimmer by measuring the power consumed during propulsion and the energy required to translate the propeller at the same speed. Finally, we discuss how the efficiency of our microswimmer could be increased upon suitable tuning of the different experimental parameters.

Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing.

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 µm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm-1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.

Magnetically tunable bidirectional locomotion of a self-assembled nanorod-sphere propeller.

Field-driven direct assembly of nanoscale matter has impact in disparate fields of science. In microscale systems, such concept has been recently exploited to optimize propulsion in viscous fluids. Despite the great potential offered by miniaturization, using self-assembly to achieve transport at the nanoscale remains an elusive task. Here we show that a hybrid propeller, composed by a ferromagnetic nanorod and a paramagnetic microsphere, can be steered in a fluid in a variety of modes, from pusher to puller, when the pair is dynamically actuated by a simple oscillating magnetic field. We exploit this unique design to build more complex structures capable of carrying several colloidal cargos as microscopic trains that quickly disassemble at will under magnetic command. In addition, our prototype can be extended to smaller nanorods below the diffraction limit, but still dynamically reconfigurable by the applied magnetic field.

Magnetic Propulsion of Recyclable Catalytic Nanocleaners for Pollutant Degradation.

Electrochemically fabricated magnetic mesoporous CoNi@Pt nanorods are excellent nanomotors with controlled magnetic propulsion and excellent catalytic properties. The core-shell structure allows a double functionality: (i) controlled motion of the nanorods by applying rotating magnetic fields at different frequencies and field strengths and (ii) effective catalytic activity of the platinum shell for reactions involving sodium borohydride. The structure and magnetic properties of the CoNi core are not modified by the presence of the Pt shell. Nanorods were propelled via a tumbling-like dynamic by a rotating magnetic field. While in absence of NaBH4, nanorods move at constant speed showing a linear path; in the presence of NaBH4, they showed an intermittent trajectory. These catalytic nanorods can be used as nanocleaners with controlled directionality for pollutants degradation in the presence of borohydride. Their magnetic character allows control of the velocity and the direction throughout the contaminated solution by degrading the different pollutants in their path. The magnetic character of nanorods also allows their easy recycling.

Radiculopatia Cervical en un paciente con ocho vértebras cervicales: presentación de un caso / Cervical Radiculopathy in a patient with eight cervical vertebras. A case presentation

Presentamos el caso clínico de radiculopatía cervical en una paciente de 43 años de edad con una historia de larga evolución de dolor cervical por más de 23 años que mejoraba con los analgésicos y antiinflamatorio, la misma presenta cervicalgia con irradiación del dolor a hombro, brazo, antebrazo, mano y región anterotoráxica; acompañado en estos últimos 6 meses de calambre en dedos de ambas manos y en la que los estudios Radiográficos demostraron la presencia de 8 vértebras cervicales con compresión de la 7ma y 8va vértebra cervical jamás conocido por la paciente. El dolor cervical es motivo de consulta frecuente en los servicios de atención médica primaria salud. El objetivo es demostrar la utilidad e importancia de realizar(AU)

Comportamiento clínico epidemiológico de la Diabetes Mellitus en pacientes mayores de 60 años / Clinical -epidemiological behaviour of diabetes mellitus in patients older than 60 years old

Introducción: la Diabetes Mellitus constituye hoy en día una verdadera epidemia mundial, debido a su alta prevalencia ya que se estima que para el 2030 supere la cifra de 435 millones, se ha convertido en un problema de desarrollo; amenaza el bienestar de las poblaciones y la prosperidad económica de los países. Objetivo: caracterizar el comportamiento clínico epidemiológico de la diabetes mellitus en la tercera edad, perteneciente al área de salud del Policlínico Docente Jimmy Hirzel, del Municipio Bayamo. Granma. Método: se realizó un estudio prospectivo, transversal y descriptivo del adulto mayor durante el período comprendido entre julio y diciembre del 2013. El universo estuvo constituido por los 200 ancianos dispensarizados como diabéticos en las historias clínicas familiares de los consultorios médicos de la familia del área de salud correspondiente al Policlínico Docente Jimmy Hirzel de Bayamo, integraron la muestra 101 gerontos (50,5 por ciento del universo) seleccionados al azar. Fueron estudiadas las siguientes variables: edad, género, tipos de diabetes, esquemas terapéuticos, adherencia terapéutica y control metabólico, siendo obtenidas mediante el interrogatorio y complementado por la revisión de las historias clínicas individuales. Resultados: la diabetes mellitus tipo 2 afectó más al grupo etáreo de 60-69 años (51,0 por ciento; P > 0,05) y al sexo femenino (60,9 por ciento). Se encontró que el 56,3 por ciento de los ancianos empleaban dieta e hipoglucemiantes orales para el control de su enfermedad (56,3 por ciento ), seguido en orden de frecuencia por la combinación de la dieta, los hipoglucemiantes orales más la insulina (20 casos; 19,5 por ciento), el 85,2 por ciento cumplían adecuadamente con el tratamiento médico, al presentar una frecuencia diaria en su administración medicamentosa, el 85,2 por ciento gozaba de un control metabólico ideal, el 19,2 por ciento presentaba un control aceptable, y solo el 2,9 por ciento tenía descontrol severo(AU)

Introduction: the Diabetes Mellitus is nowadays a true world-wide epidemic, because of its high prevalence, since it is estimated that in the year 2030 it will surpass the amount of 435 millions of ill persons, it has turned into an increasing problem; threatening the welfare of the populations and the economic prosperity of the countries. Objective: to characterize the clinical epidemiological behaviour of the diabetes mellitus in the third age, belonging to the health area of the Educational Polyclinic Jimmy Hirzel, in Bayamo Municipality, Granma. Method: it was performed a prospective, transversal and descriptive study of the elders during the period comprised between July and December of the 2013. The universe was constituted by the 200 dispensarized elders like diabetics in the family clinical records of the family medical office of the health area that belongs to the Educational Polyclinic Jimmy Hirzel of Bayamo. The sample was integrated by 101 geronts (50,5 percent of the universe) selected at random. There were studied the following variables: age, gender, types of diabetes, therapeutic diagrams, therapeutic adherence and metabolic control, they were obtained by means of the interrogation and complemented by the review of the individual clinical histories. Results: the diabetes mellitus type 2 mostly affected the age group of 60-69 years (51,0 percent; P > 0, 05) and the feminine sex (60,9 percent). It was found that the 56,3 percent of the elderly applied diet and oral hypoglycemiants for the control of their illness (56,3 percent ), followed by the combination of the diet, the oral hypoglycemiants and the insulin ( 20 cases; 19,5 percent), the 85,2 percent fulfilled properly with the medical treatment, when presenting a daily frequency in the medicine administration, the 85,2 percent enjoyed an ideal metabolic control, the 19,2 percent presented an acceptable control, and only the 2,9 percent had severe disorders(EU)

Calidad de vida en paciente con accidente cerebro vasculares en atención primaria de salud / Life quality in patients with cerebrovascular accident in the primary health care

La calidad de vida relativa a salud es un indicador confiable y necesario para el análisis del estado sanitario de una comunidad y fuente de datos para definir estrategias en las acciones de salud sobre una población. El objetivo del presente trabajo es describir aspectos relacionados con la calidad de vida en pacientes supervivientes por dos años a enfermedad cerebrovascular. Se realizó un estudio descriptivo, de serie de casos, con evaluación de la calidad de vida relacionada con salud en pacientes con dos años de egresados por ictus. Se realizó un muestreo aleatorio simple aplicado a los supervivientes. Se utilizó la escala de calidad de vida para el ictus, determinando los dominios más afectados con aplicación de técnicas estadísticas. La evaluación de la calidad de vida en ictus mostró una media de puntaje general de 46,5; las esferas identificadas como más comprometidas fueron los sentimientos y las emociones. Se constató afección en varios de los dominios en la mayoría de los supervivientes, aunque las mensuraciones obtenidas no fueron altas. El grado de recuperación a los dos años fue poco o nada en 41 enfermos, los datos obtenidos fueron representados en tablas y gráficos. Las alteraciones de la calidad de vida relacionada con la salud son secuelas que en mayor o menor grado padece la gran mayoría de los sobrevivientes a un neuroictus, estas pueden ser determinadas aplicando la escala de calidad de vida para el ictus. Es necesario adoptar medidas para minimizar los efectos deletéreos de estas afecciones y cumplir el objetivo de que los sobrevivientes tengan una calidad de vida satisfactoria(AU)

The health life quality is a reliable and necessary indicator for the analysis of the sanitary state of a community and a source of data to define strategies in the health actions on a population. The aim of the present work is to describe aspects related to the life quality in patients that survive the cerebrovascular conditions for two years. It was performed a descriptive study, of case series, with the evaluation of the life quality related to health in two-year-withdrawed patients for ictus. It was made a simple random sampling applied to the survivors. It was used the scale of quality of life for the ictus, determining the most affected commands with application of statistical techniques. The evaluation of the quality of life in ictus showed an average of general score about 46,5; the identified spheres as more committed were the feelings and the emotions. It was evidenced the injure condition in most of the survivors, although the measurements obtained were not high. The degree of recovery after two years was scarce or none in 41 patients, the data obtained were represented in tables and charts. The alterations of the quality of life related with the health are sequels that in higher or lower degree suffers the great majority of the survivors to a neuroictus, these can be determined applying the scale of quality of life for the ictus. It is necessary to adopt measures to minimize the deleterious effects of these conditions and fulfill the aim for the survivors to have a satisfactory quality of life(EU)

Measurement of the giant magnetoresistance effect in cobalt-silver magnetic nanostructures: nanoparticles.

Cobalt-silver (Co-Ag) core-shell nanoparticles with different silver thicknesses were prepared by the microemulsion method in a two-step reduction process. Transmission electron microscopy (TEM) characterization revealed the almost monodispersity and nanometric size (in the range 3-5 nm depending on the shell thickness) of the synthesized nanoparticles. However, it was the use of high-resolution TEM that revealed the correct core-shell formation of the nanometric material. The selected area electron diffraction pattern indicated the fcc (face-centered cubic) and hcp (hexagonal close packed) nature for silver and cobalt, respectively. Cyclic voltammetry also allowed the correct core-shell formation to be assured. The magnetic properties revealed the presence of both superparamagnetic and ferromagnetic contributions. Because of the lack of methodology, it was necessary to develop a method to measure the magnetotransport properties of the prepared nanoparticles. The strategy which followed was successful as it was possible to measure these properties: giant magnetoresistance values of 0.1% at room temperature were obtained. The numerical analysis of magnetic and magnetoresistance data indicated the presence of superparamagnetic particles showing interaction among the magnetic moments.

Electrodeposition of Co-Ag films and compositional determination by electrochemical methods.

An electrolytic bath containing silver(I), cobalt(II) and different complexing agents to electrodeposit Co-Ag coatings over vitreous carbon and silicon/seed-layer substrates is proposed. In situ electrochemical characterization of thin deposits is performed by means of stripping (potentiodynamic or galvanostatic) methods. These techniques allow detecting the heterogeneous codeposition of cobalt and silver. Electrochemical ex situ methods (polarographic and voltammetric methods) are implemented to quantify the silver and cobalt percentage in the coatings. Optimal analytical parameters for voltammetric method are established.