Gabriel Ybarra | Instituto Nacional de Tecnología Industrial (original) (raw)

Papers by Gabriel Ybarra

Journal of Electroanalytical Chemistry, Jun 1, 2022

Journal of Electrochemical Science and Engineering, Dec 22, 2017

The activity of a peroxidase-mimicking DNAzyme was optimized to be used as a catalytic label in a... more The activity of a peroxidase-mimicking DNAzyme was optimized to be used as a catalytic label in a stem-loop genosensor construction for quantifying the gene sequence Shiga-like toxin I of verotoxigenic E. coli. Experimental conditions such as pH, buffer composition, potassium ion concentration, and hemin-to-oligonucleotides ratio, were analyzed to maximize optical and electrochemical responses using microvolumes. Different stem-loop constructions were evaluated to obtain the optimum response against the target concentration. Linear ranges of 0.05-0.5 µM and limits of detection of 174 nM and 144 nM were estimated for the optical and electrochemical measurements, respectively. Selectivity was proved by assaying other verotoxigenic, enterotoxigenic and enteroinvasive sequences. The results show that, if a combination of small-volume electrochemical cells and low-cost untreated screen-printed electrodes with a relatively high geometric area is used, electrochemical measurements present similar sensitivity and limits of detection to the more usual optical ones, allowing the development of lowcost electrochemical biosensors based on the use of soluble DNAzymes as labels.

Polymer Testing, Aug 1, 2005

ABSTRACT The goal of this paper is to present a method to determine the time evolution of epoxy c... more ABSTRACT The goal of this paper is to present a method to determine the time evolution of epoxy conversion for epoxy/amine and epoxy/amide formulations in heterogeneous systems such as paints by means of near infrared (NIR) spectroscopy. The cure reaction involves a simple addition mechanism between the oxirane ring and the amine/amide hydrogen functional groups. The extent of the reaction was calculated from the NIR absorption band at around 4530 cm−1 which depends on the oxirane rings concentration. The NIR spectroscopic method, which has the advantage of real time analysis over other techniques such as chemical titration, can be employed with most of the usual, modern FTIR spectrometers.

Journal of Electroanalytical Chemistry, Apr 1, 1997

The electrochemical behaviour and solid state properties of passive oxide !ayers formed on binary... more The electrochemical behaviour and solid state properties of passive oxide !ayers formed on binary fin + iadium alloys in alkaline aqueous solution were studied by using photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). Results obtained from PCS and EIS measurements showed that the anodically formed tin oxides behaved as heavily doped, n-type amorphous semiconductors. From the photocurrent spectra the mobility gap energies of different passive layers were evaluated. The mobility gap exhibited a remarkable dependence on the alloy composition, shifting towards higher energies as the indium content in the alloy was increased. Impedance diagrams displayed a complex frequency response and the corresponding transfer function analysis employing both parametric identification procedures and non-linear fit routines, presented several contributions. The apparent fiat-band potential obtained from Mott-Schottky plots depended on alloy composition, shifting more negatively with increasing indium content. On the basis of PCS and EIS data, a tentative scheme of the valence and conduction mobility edge energies for the different passive films was postulated and its correlation with the oxide layer composition critically discussed.

Wear, Feb 1, 2006

In the present work, industrial-scale DC-pulsed plasma nitriding for 20 h at 673 K was used to im... more In the present work, industrial-scale DC-pulsed plasma nitriding for 20 h at 673 K was used to improve the wear resistance of an AISI 410 martensitic stainless steel. The tribological behaviour was studied and compared to the behaviour of the same steel in as-received condition. Pin-on-disc dry tests, using an alumina ball as counter-body, were carried out to determine the evolution of the friction coefficient. The wear resistance was investigated using an Amsler-disc-machine, employing a dry combined contact of rolling-sliding with three different applied loads. The wear mechanisms involved during rolling-sliding of unnitrided and plasma nitrided steels were investigated by microscopic observation of the surfaces, the corresponding cross-sections and the produced wear debris. The combination of different wear mechanisms taking place in the wear process of unnitrided and nitrided materials were discussed and analyzed. In contrast to the unnitrided steel, DC-pulsed plasma nitrided samples presented an improvement in the friction coefficient and the wear rate.

DOAJ (DOAJ: Directory of Open Access Journals), Mar 1, 2015

An amperometric biosensor for the quantification of food allergens based on an inhibitory immunoa... more An amperometric biosensor for the quantification of food allergens based on an inhibitory immunoassay is presented. As a proof of concept, the experimental conditions were optimized for the detection of β-casein in the 0-10 ppm range. Eight electrochemical cells were integrated into a small-sized portable potentiostat controlled by a smartphone via Bluetooth communication. The determination of β-casein in eight different samples can be measured with the electrochemical biosensor, which has the potential to be modified for the detection of multiple allergens.

Educación Química

Understanding the electrochemical sensors' figures of merit using a H 2 O 2 sensitive, low-cost f... more Understanding the electrochemical sensors' figures of merit using a H 2 O 2 sensitive, low-cost ferrite powder first generation electrode. Educación Química, 33(2).

Matéria (Rio de Janeiro), 2020

Chemical and physical methods have been generally used for modifying the surface of titanium impl... more Chemical and physical methods have been generally used for modifying the surface of titanium implants with the aim of achieving better osseointegration. In this work, an evaluation of the effect of different chemicals and thermochemical treatments on the surface modification of titanium was carried out. Plates of commercially pure titanium were polished and treated with four different methods. Scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, X-ray diffraction and drop shape analysis were used to characterize the modified titanium surface. Our results showed that the AEPTTT surface exhibited the highest Ra values followed by AEAT, AEPT, polished Ti and AE samples. In addition, the AEAT and AEPTTT treatments developed the largest surface area, while the AE treatment produced the lowest surface area. Furthermore, the AEAT treatment created the most hydrophilic surface, which is known to positively affect the osseointegration rate of dental implants.

Chemosensors

Sweat analysis by means of minimally invasive wearable sensors is considered a potentially disrup... more Sweat analysis by means of minimally invasive wearable sensors is considered a potentially disruptive method for assessing clinical parameters, with exciting applications in early medical diagnostics and high-performance sports. Electrochemical sensors and biosensors are especially attractive because of the possibility of the electronic integration of wearable devices. In this article, we review several aspects regarding the potentialities and present limitations of electrochemical sweat (bio)sensors, including: the main target analytes and their relationships with clinical conditions; most usual electrochemical techniques of transduction used according to the nature of the target analytes; issues connected to the collection of representative sweat samples; aspects regarding the associated, miniaturized electronic instrumentation used for signal processing and communication; and signal processing by machine learning.

Journal of Magnetism and Magnetic Materials

Surface and Coatings Technology, 2017

Plasma nitriding of 316L stainless steel in two different N 2-H 2 atmospheres-Influence on micros... more Plasma nitriding of 316L stainless steel in two different N 2-H 2 atmospheres-Influence on microstructure and corrosion resistance

Química Nova, 2016

The biomimetic method is used for the deposition of calcium phosphate coatings (Ca-P) on the surf... more The biomimetic method is used for the deposition of calcium phosphate coatings (Ca-P) on the surface of different biomaterials. However, the application of this method requires long exposure times in order to obtain a suitable layer thickness for its use in medical devices. In this paper, we present a fast approach to obtain apatite coatings on titanium, using a combination of supersaturated calcification solution (SCS) with chemical modification of the titanium surface. Also, it was evaluated the effect of four different surface treatments on the apatite deposition rate. Commercially pure titanium plates were activated by chemical or thermochemical treatments. Then, the activated samples were immersed in a solution with high content of calcium and phosphate ions at 37 °C for 24 h, mimicking the physiological conditions. The coatings were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The use of SCS solutions allowed the formation of crystalline hydroxyapatite coatings within a period of 24 h with a thickness between 1 and 5.3 μm. Besides, precipitates of hydroxyapatite nanoparticles with a globular configuration, forming aggregates with submicrometer size, were found in SCS solutions.

Journal of Biotechnology, 2016

Highlights  DNA aptamers recognize membrane-damaged bovine sperm cells  Superparamagnetic iron ... more Highlights  DNA aptamers recognize membrane-damaged bovine sperm cells  Superparamagnetic iron oxide nanoparticles remove aptamer-bound damaged cells from sperm suspensions  Improved semen quality was achieved in both unsorted and sex-sorted bovine sperm suspensions  Removal of damaged sperm cells with DNA aptamers and nanoparticles does not affect embryo development

The Chemical Educator

In this paper, the diffusion process is illustrated with the example of a chess king moving at ra... more In this paper, the diffusion process is illustrated with the example of a chess king moving at random on a chessboard. The displacement of the king can be easily analyzed because both the geometry of the chessboard and the king's movements are well defined. In addition to the usual mathematical analysis of binomial and normal distributions for the random trajectories, very simple algorithms are introduced to follow the possible random trajectories and, in that sense, the stated problem might be a suitable introduction to computer simulations. The variety of concepts and tools employed to analyze this problem make it an agreeable and didactic exercise for undergraduate students of a physical chemistry course.

Objetivo del Proyecto: Desarrollo de sensores para la determinación de la demanda bioquímica de o... more Objetivo del Proyecto: Desarrollo de sensores para la determinación de la demanda bioquímica de oxígeno, una medida del oxígeno consumido por microorganismos en el proceso de degradación de materia orgánica. La demanda bioquímica de oxígeno es un parámetro necesario en el análisis de efluentes industriales y en el monitoreo de la polución orgánica en aguas residuales.

Este libro de texto se presenta como un complemento a los libros de inmunologia basica y de tecni... more Este libro de texto se presenta como un complemento a los libros de inmunologia basica y de tecnicas inmunologicas. Libro de consulta para estudiantes de Biologia, Biotecnologia, Medicina, Veterinaria y otras areas biomedicas y para profesionales.

In this paper, the dynamics of electrode reactions under diffusion-migration control is analyzed ... more In this paper, the dynamics of electrode reactions under diffusion-migration control is analyzed with an approach based on random walks. The main advantage of this approach is the simplicity of the concepts involved which lead to very simple computational algorithms, avoiding the resolution of differential equations. The model was employed to obtain the profile concentrations of reversible electrode reactions, as well as current transients, for the case where diffusion and migration have comparable effects.

Immunosensors are compact analytical devices in which the event of formation of antigenantibody c... more Immunosensors are compact analytical devices in which the event of formation of antigenantibody complexes is detected and converted, by means of a transducer, to an electrical signal, which can be processed, recorded and displayed. Different transducing mechanisms are employed in immunological biosensors, based on signal generation (such as an electrochemical or optical signal) or properties changes (such as mass changes) following the formation of antigen-antibody complexes. In this chapter, the basics of immunosensors are presented focused on the different transduction techniques used in immunosensing.