Iridium oxide based potassium sensitive microprobe with anti-fouling properties

Here, we present a new type of potassium sensor which possesses a combination of potassium sensing and anti-biofouling properties. Two major advancements were required to be developed with respect to the current technology; Firstly, design of surface linkers for this type of coating that would allow deposition of the potassiumselective coating on Iridium (Ir) wire or micro-spike surface for chronic monitoring for the first time. As this has never been done before, even for flat Ir surfaces, the material’s small dimensions and surface area render this challenging. Secondly, the task of transformation of the coated wire into a sensor. Here we develop and bench-test the electrode sensitivity to potassium and determine its specificity to potassium versus sodium interference. For this purpose we also present a novel characterisation platform which enables dynamic characterization of the sensor including step and sinusoidal response to analyte changes. The developed sensor shows good sensitivity (<1 mM concentrations of K+ ions) and selectivity (up to approximately 10 times more sensitive to K+ than Na+ concentration changes, depending on concentrations and ionic environment). In addition, the sensor displays very good mechanical properties for the small diameter involved (sub 150 μm), which in combination with anti-biofouling properties, renders it an excellent potential tool for the chemical monitoring of neural and other physiological activities using implantable devices

Capacidad antagónica in vitro de Trichoderma spp frente a Sclerotium spp y promotor del crecimiento vegetal en plantulas de frijol (Phaseolus Vulgaris L.) UNA, Managua 2021

El cultivo de frijol (Phaseulus vulgaris L.), es uno de los cultivos de importancia económica en Nicaragua, representado por pequeños y medianos productores de los cuales consumen un 96 % toda la población nicaragüense. los pequeños productores de frijol tienen grandes limitaciones entre estas los problemas fitosanitarios siendo Sclerotium spp una de las enfermedades del frijol que ha venido en aumento y manejada principalmente con un uso indiscriminado de funguicida por lo que es necesario la búsqueda de alternativas de control. Asimismo, la razón principal de nuestro estudio es generar información del efecto antagónico de Trichoderma spp sobre agente causal de la pata prieta Sclerotium spp en el cultivo de frijol bajo condiciones In vitro e invernadero. Los datos obtenidos fueron analizados mediante análisis de varianza y separación de medias según Tukey. a las 18 horas se registró el menor ritmo de crecimiento con 1 mm y el mayor ritmo de crecimiento se presentó a las 84 horas con 12 mm cubriendo completamente el plato Petri, para el patógeno se registró el menor ritmo de crecimiento con el aislado SCLPP con 3.25 mm y el crecimiento radial para todo los aislados se presentó variable siendo el mayor ritmo de crecimiento a las 45 horas con 10.95 mm. Para los aislados de Sclerotium spp (SCLAJ, SCLF) mostraron los PICR inhibición más alto con (96.79 y 98.69 porciento) a las 84 y 98 horas siendo enfrentado a las cepas antagonista resultando con un promedio de 53.24 y 63.3 con el asilado antagonista RFIII. El aislado THR incremento la altura de la planta con 66.83 cm y aumento el número de hojas trifoliadas con 6.83 hojas

Relación de los sistemas de grupos sanguíneos ABO y Rhesus con el número de veces de infección por Plasmodium vivax y Plasmodium falciparum en pobladores que fueron diagnosticados con malaria del Municipio de Puerto Cabeza, RACCN entre Octubre 2019 a Marzo 2020

Se realizó un estudio de enfoque cuantitativo, de corte transversal con el objetivo de analizar la relación de los grupo sanguíneos ABO y Rhesus con el número de veces de infección por Plasmodium vivax y P. falciparum en pobladores con episodios malaricos, del Municipio de Puerto Cabezas RACCN, entre Octubre 2019 a Marzo 2020. El universo estuvo conformado por los pobladores del Municipio de Puerto Cabeza a los que se les había realizado la prueba para diagnosticar malaria, y la muestra estuvo conformada por 155 pobladores que dieron positivo para malaria (gota gruesa), las edades comprendidas fueron de 1 a 60 años, en lo que respecta al sexo un 61% fue femenino y un 39% masculino, se realizó prueba directa e inversa para la detección de fenotipos sanguíneos; donde se obtuvieron los siguientes resultados: el grupo sanguíneo predomínate fue el O+ con una frecuencia de 60.6%, seguidamente el tipo sanguíneo fue el A+ con una incidencia de 21.3%, posteriormente el B+ con un 11%, luego el grupo sanguíneo AB+ 3.9 %, y por último el B- con 0.6% y O- con 2.6% cabe mencionar que no se encontraron fenotipos A- y AB-. El grupo A+ presentó los picos más altos en lo que respecta al número de veces de infección por malaria, donde 14 pobladores que representa el 41,17% del 100% del grupo A+ tuvieron de 10 a 12 episodios a lo largo de su vida y 16 (47,05%) pobladores del mismo grupo sanguíneo tuvieron de 13 a 15 veces episodios malaricos. A pesar de que el grupo sanguíneo O+ es el más común, los episodios malaricos fueron menos frecuent

Detection of Lysophosphatidic Acid in Serum; Towards a Cost Effective Test for Ovarian Cancer

Ovarian cancer is a disease that affects a quarter of a million new women and causes over 140,000 deaths worldwide annually. This is primarily due to how difficult the disease is to detect, with few symptoms present in the early stages of the disease and difficult to physically feel masses. Currently detection of ovarian cancer requires time consuming and expensive imaging studies such as transvaginal ultrasound and MRI scans, which are only performed if it is already suspected that a woman has the disease. The only currently accepted blood test for ovarian cancer detects the biomarker CA-125, but this test is only sensitive to 50% of cases and as a result is rarely used for signaling the presence of the cancer. There is another biomarker for ovarian cancer called lysophosphatidic acid (LPA) which has a sensitivity and specificity of over 90% for the disease, making it promising for use in testing for ovarian cancer. There are currently no low cost or easy to perform blood tests for LPA, preventing its use as a general test that can be performed at yearly physicals. However there is a duel protein system comprised of Gelsolin and Actin which is interrupted by interactions with LPA, which can therefore be used to develop a low cost blood test for the marker. These proteins could be bound to a biosensing surface, and the release of actin as a result of LPA would generate a measurable signal. Studying the fouling behaviour of LPA and serum on transverse shear mode biosensors, also known as quartz crystal microbalances, showed that the background fouling signal was too large for a test to be developed on this class of devices. Instead a test based on colorometric sensing of dye modified actin was conceived and evaluated. This test comprised of the protein gelsolin being bound to solid phase in a way capable of holding onto the protein in serum samples. The gelsolin was also be bound to a fluorescent dye modified actin that could be measured using colorimetric absorbance or fluorescence. These proteins were successfully created, and shown to create a complex that could be broken by LPA in a concentration dependent manner. Immobilization of this protein complex was performed on silica gel, using Ni-NTA which was attached to the surface via a trichlorosilane linker functionalized with an acid chloride head group, which was first synthesized in these experiments. Several conditions in the development of the surface Ni-NTA adlayer and subsequent protein immobilization were evaluated, and it was found that such things as a large pore size in the silica gel, removal of excess toluene from the surface following adlayer addition, and adequate washing and drying of the silica were all of crucial importance to the performance of this test in serum. Development of this test showed promise in quantifying LPA at biologically relevant concentrations, however more work needs to be done to lower the limit of detection to a point below the cut-off level for ovarian cancer. Crucially this test is very cheap to produce, and requires little human labour to perform which are characteristics required for its wide scale adoption in ovarian cancer screening.Ph.D

Surface Adsorption of the Cancer Biomarker Lysophosphatidic Acid in Serum Studied by Acoustic Wave Biosensor

The thickness shear mode acoustic wave device is of interest for the sensing of biomarkers for diseases in various biological fluids, but suffers from the issue of non-specific adsorption of compounds other than those of interest to the electrode surface, thus affecting the device’s output. The aim of this present study was to determine the level of non-specific adsorption on gold electrodes from serum samples with added ovarian cancer biomarker lysophosphatidic acid in the presence of a surface anti-fouling layer. The latter was an oligoethylene molecule with thiol group for attachment to the electrode surface. It was found that the anti-fouling layer had a minimal effect on the level of both adsorption of components from serum and the marker. This result stands in sharp contrast to the analogous monolayer employed for anti-fouling reduction on silica

Anti-Thrombogenicity Study of a Covalently-Attached Monolayer on Stent-Grade Stainless Steel

Implantable devices fabricated from austenitic type 316L stainless steel have been employed significantly in medicine, principally because the material displays excellent mechanical characteristics and corrosion resistance. It is well known, however, that interaction of exposure of such a material to blood can initiate platelet adhesion and blood coagulation, leading to a harmful medical condition. In order to prevent undesirable surface platelet adhesion on biomaterials employed in procedures such as renal dialysis, we developed an ultrathin anti-thrombogenic covalently attached monolayer based on monoethylene glycol silane chemistry. This functions by forming an interstitial hydration layer which displays restricted mobility in the prevention of surface fouling. In the present work, the promising anti-thrombogenic properties of this film are examined with respect to platelet aggregation on 316L austenitic stainless steel exposed to whole human blood. Prior to exposure with blood, all major surface modification steps were examined by X-ray photoelectron spectroscopic analysis and surface free-angle measurement by contact angle goniometry. End-stage anti-thrombogenicity detection after 20 min of blood exposure at 100 s−1, 300 s−1, 600 s−1, 750 s−1, and 900 s−1 shear rates revealed that a significant reduction (&gt;90%) of platelet adhesion and aggregation was achieved for surface-modified steel, compared with untreated material. This result is confirmed by experiments conducted in real time for 60-minute exposure to blood at 100 s−1, 600 s−1, and 900 s−1 shear rates

Anti-Thrombogenicity Study of a Covalently-Attached Monolayer on Stent-Grade Stainless Steel

Implantable devices fabricated from austenitic type 316L stainless steel have been employed significantly in medicine, principally because the material displays excellent mechanical characteristics and corrosion resistance. It is well known, however, that interaction of exposure of such a material to blood can initiate platelet adhesion and blood coagulation, leading to a harmful medical condition. In order to prevent undesirable surface platelet adhesion on biomaterials employed in procedures such as renal dialysis, we developed an ultrathin anti-thrombogenic covalently attached monolayer based on monoethylene glycol silane chemistry. This functions by forming an interstitial hydration layer which displays restricted mobility in the prevention of surface fouling. In the present work, the promising anti-thrombogenic properties of this film are examined with respect to platelet aggregation on 316L austenitic stainless steel exposed to whole human blood. Prior to exposure with blood, all major surface modification steps were examined by X-ray photoelectron spectroscopic analysis and surface free-angle measurement by contact angle goniometry. End-stage anti-thrombogenicity detection after 20 min of blood exposure at 100 s−1, 300 s−1, 600 s−1, 750 s−1, and 900 s−1 shear rates revealed that a significant reduction (&gt;90%) of platelet adhesion and aggregation was achieved for surface-modified steel, compared with untreated material. This result is confirmed by experiments conducted in real time for 60-minute exposure to blood at 100 s−1, 600 s−1, and 900 s−1 shear rates

Assembling Surface Linker Chemistry with Minimization of Non-Specific Adsorption on Biosensor Materials

The operation of biosensors requires surfaces that are both highly specific towards the target analyte and that are minimally subject to fouling by species present in a biological fluid. In this work, we further examined the thiosulfonate-based linker in order to construct robust and durable self-assembling monolayers (SAMs) onto hydroxylated surfaces such as silica. These SAMs are capable of the chemoselective immobilization of thiol-containing probes (for analytes) under aqueous conditions in a single, straightforward, reliable, and coupling-free manner. The efficacy of the method was assessed through implementation as a biosensing interface for an ultra-high frequency acoustic wave device dedicated to the detection of avidin via attached biotin. Fouling was assessed via introduction of interfering bovine serum albumin (BSA), IgG antibody, or goat serum. Improvements were investigated systematically through the incorporation of an oligoethylene glycol backbone employed together with a self-assembling diluent without a functional distal group. This work demonstrates that the incorporation of a diluent of relatively short length is crucial for the reduction of fouling. Included in this work is a comparison of the surface attachment of the linker to Si3N4 and AlN, both materials used in sensor technology

Long-Term Reduction of Bacterial Adhesion on Polyurethane by an Ultra-Thin Surface Modifier

Indwelling urinary catheters are employed widely to relieve urinary retention in patients. A common side effect of the use of these catheters is the formation of urinary tract infections (UTIs), which can lead not only to severe medical complications, but even to death. A number of approaches have been used to attempt reduction in the rate of UTI development in catheterized patients, which include the application of antibiotics and modification of the device surface by coatings. Many of these coatings have not seen use on catheters in medical settings due to either the high cost of their implementation, their long-term stability, or their safety. In previous work, it has been established that the simple, stable, and easily applicable sterilization surface coating 2-(3-trichlorosilylpropyloxy)-ethyl hydroxide (MEG-OH) can be applied to polyurethane plastic, where it greatly reduces microbial fouling from a variety of species for a 1-day time period. In the present work, we establish that this coating is able to remain stable and provide a similarly large reduction in fouling against Escherichia coli and Staphylococcus aureus for time periods in an excess of 30 days. This non-specific coating functioned against both Gram-positive and Gram-negative bacteria, providing a log 1.1 to log 1.9 reduction, depending on the species and day. This stability and continued efficacy greatly suggest that MEG-OH may be capable of providing a solution to the UTI issue which occurs with urinary catheters

Advances in Electromagnetic Piezoelectric Acoustic Sensor Technology for Biosensor-Based Detection

The ultra-high frequency EMPAS (electromagnetic piezoelectric acoustic sensor) device is composed of an electrode-less quartz disc in which shear oscillation is induced by an AC-powered magnetic coil located 30 μm below the substrate. This configuration allows the instigation of high acoustic harmonics (in the region of 49th–53rd), with the resulting enhanced analytical sensitivity for biosensor purposes compared to the conventional thickness-shear mode device. In this paper, we introduce significant improvements to the operation of the system with respect to sensing applications. This includes a new interface program and the capability to measure the acoustic quality factor not available in the prototype version. The enhanced configuration is subject to testing through biosensor detection of surface adsorption of biological macromolecules, which include β-casein, and a gelsolin-actin complex