Utilization of special potential scan programs for cyclic voltammetric development of different nickel oxide-hydroxide species on Ni based electrodes

Special potential scan programs were designed for cyclic voltammetric development of β-NiOOH or γ-NiOOH/ β-NiOOH mixtures on the surface of nickel or nickel-chromium (80:20) alloy electrodes in NaOH 0.10 M. The programs consisted on changing the anodic or cathodic switching limit to facilitate the chemical reactions taking place either between Ni(II) hydroxides or between Ni(III) oxides-hydroxides. The electrochemical charge density under the oxidative wave, observed at Ni or Ni-Cr electrode surfaces at approximately 0.48 V (vs SCE), remained almost con- stant with the number of cv cycles after approximately 600 cv cycles at 0.050 V/s. Thus, it can be suggested that a stable proportion of Ni(II)/Ni(III) oxides-hydroxides was obtained on the electrode surfaces. The relative amounts of β-NiOOH or γ-NiOOH species were calculated from the electrochemical charges under their reduction waves in the voltammetric experiments. Higher charge densities were always obtained with Ni-Cr alloy electrodes as compared to pure Ni electrodes. Linear relationships were obtained in our study on the dependence of the oxidative peak current with the square root of the scan rate at a scan rate range between 0.01 V/s and 0.16 V/s.Facultad de Ciencias Exacta

Ventilator-associated pneumonia treatment: mortality cofactor in positive COVID-19 patients

El objetivo general de este trabajo es contribuir a la prevención de la NAV por medio de la funcionalización de las superficies interna y externa del tubo endotraqueal empleado en la ventilación mecánica. La modificación se realiza mediante el depósito de una delgada película de hidrogeles biocompatibles y biodegradables cargados con agentes antimicrobianos convencionales (antibióticos) y no convencionales (nanopartículas de plata, AgNPs) para combatir la formación de los biofilms bacterianos que generan la NAV. Los hidrogeles proporcionan control espacial y temporal sobre la liberación de los agentes terapéuticos debido a su degradabilidad controlable y capacidad para proteger a los medicamentos lábiles, permitiendo, además, alcanzar concentraciones locales superiores a las obtenidas por administración sistémica. Para alcanzar los objetivos, se ha optimizado la síntesis de un hidrogel en base a polietilenglicol capaz de adherirse fuertemente a la superficie de cloruro de polivinilo del tubo endotraqueal. Se logró recubrir la superficie del tubo con el hidrogel, comprobándose una buena estabilidad mecánica tanto para el hidrogel deshidratado como para el mismo hidratado. Se analizaron diferentes rutas de incorporación de los agentes antimicrobianos, encontrándose que la más adecuada es el agregado de éstos al polímero precursor del hidrogel. Los hidrogeles modificados con AgNPs presentan características de adhesión y estabilidad similares a las de los hidrogeles sin modificar. Al momento de escribir este trabajo se están llevando cabo los experimentos tendientes a determinar la capacidad antimicrobiana de las superficies modificadas.The general objective of this work is to contribute to the prevention of VAP through the functionalization of the internal and external surfaces of the endotracheal tube used in mechanical ventilation. The modification is carried out by depositing a thin film of biocompatible and biodegradable hydrogels loaded with antibiotics and non-conventional antimicrobial agents (silver nanoparticles, AgNPs) to inhibit the formation of bacterial biofilms generating NAV. Hydrogels provide spatial and temporal control over the release of therapeutic agents due to their controllable degradability and ability to protect labile drugs. In addition, higher antibiotic local concentration than those obtained by systemic administration can be reached. To achieve these objectives, the synthesis of a hydrogel based on polyethylene glycol which is capable of strongly adhere to the polyvinyl chloride surface of the endotracheal tube has been optimized. It was possible to cover the surface of the tube with the hydrogel, which showed good mechanical stability for both the dehydrated hydrogel and the hydrated one. Different routes of incorporation of antimicrobial agents were investigated, finding that the most suitable is the addition of these agents to the precursor polymer of the hydrogel. Hydrogels loaded with AgNPs have similar adhesion and stability to the unloaded hydrogels. Experiments are being carried out to determine the antimicrobial capacity of these modified surfaces.Este desarrollo es financiado mediante el Programa de Articulación y Fortalecimiento Federal de las Capacidades en Ciencia y Tecnología COVID-19, Ministerio de Ciencia, Tecnología e Innovación, Argentina (2020).Secretaría de Ciencia y Técnic

HIDROGELES BIODEGRADABLES SOBRE SUPERFICIES DE INTERÉS EN CIRUGÍA PROTÉSICA: HACIA UN SISTEMA ÓPTIMO PARA LA LIBERACIÓN LOCAL DE AGENTES TERAPÉUTICOS

La incorporación al cuerpo de biomateriales en forma de tornillos, alambres, clavos, etc. es una práctica quirúrgica generalizada para mantener los huesos dañados en su alineación adecuada o para reemplazar hueso dañado o tejido conectivo. Las funciones del biomaterial pueden verse comprometidas por diversos factores, tales como las características del paciente (enfermedades crónicas), factores locales (sitio anatómico difícil, infección, etc.) y factores quirúrgicos (técnica quirúrgica, características inadecuadas del implante, etc.). Esto ha estimulado la investigación sobre alternativas terapéuticas para la administración local de compuestos, que posee varias ventajas frente a los tratamientos farmacológicos sistémicos, como la administración específica de uno o más productos en el sitio de la lesión, una menor dosis, y la mitigación de efectos secundarios potencialmente graves. Una de estas estrategias es el recubrimiento de los dispositivos implantables con hidrogeles como vehículo de administración local de agentes terapéuticos. Debido a sus propiedades físicas sintonizables, degradabilidad controlable y capacidad para proteger a los medicamentos lábiles, sirven como una plataforma para controlar la liberación, espacial y temporal, de dichos agentes terapéuticos, pudiendo alcanzarse concentraciones superiores a las obtenidas mediante la funcionalización directa de las superficies. Por otro lado, el Ti y sus aleaciones son los materiales más utilizados en dispositivos implantables ortopédicos debido a sus propiedades mecánicas y de biocompatibilidad. El objetivo del plan de trabajo es diseñar procedimientos para recubrir de Ti con hidrogeles biodegradables, particularmente polietilenglicol malato-citrato (PEGMC), que permitan la incorporación de agentes terapéuticos y cuya función sea regular la interacción del material con los tejidos y/o sean capaces de inhibir la adhesión de microorganismos. Para este fin, se optimizará la síntesis de los hidrogeles y se diseñarán tanto la ruta de funcionalización de Ti como los protocolos adecuados para la incorporación de agentes terapéuticos (antimicrobianos, convencionales y alternativos, factores de regeneración celular, etc.). Se caracterizarán las superficies modificadas desde el punto de vista fisicoquímico y se analizará su desempeño en entornos biológicos adecuados (cultivos celulares, cultivos bacterianos).  Las superficies desarrolladas permitirán la acción sostenida en el tiempo de los agentes terapéuticos, mediante su liberación progresiva al medio, la que será impulsada por gradientes de concentración y mediada por la biodegradación del hidrogel. &nbsp

Multifunctional Titanium Surfaces for Orthopedic Implants: Antimicrobial Activity and Enhanced Osseointegration

The use of implants in orthopedics and dental practice is a widespread surgical procedure to treat diverse diseases. However, peri-implantitis due to infections and/or poor osseointegration can lead to metallic implant failure. The aim of this study was to develop a multifunctional coating on titanium (Ti) surfaces, to simultaneously deal with both issues, by combining antibacterial silver nanoparticles (AgNPs) and regenerative properties of lactoferrin (Lf). A simple and cost-effective methodology that allows the direct multifunctionalization of Ti surfaces was developed. The modified surfaces were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and contact angle measurements. Additionally, in vitro preosteoblast cell adhesion, cell viability, and differentiation were evaluated. The antibacterial capability of the surfaces was tested against Staphylococcus aureus as a prosthesis infection model strain. Our results showed that Lf adsorbed on both Ti surfaces and Ti surfaces with adsorbed AgNPs. Simultaneously, the presence of Lf and AgNPs notably improved preosteoblast adhesion, proliferation, and differentiation, whereas it reduced the bacterial colonization by 97.7%. Our findings indicate that this simple method may have potential applications in medical devices to both improve osseointegration and reduce bacterial infection risk, enhancing successful implantation and patients' quality of life.Fil: Ghilini, Fiorela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Fagali, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Pissinis, Diego Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Benitez, Guillermo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Schilardi, Patricia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Is the biocompatibility of copper with polymerized natural coating dependent on the potential selected for the electropolymerization process?

With the intention of taking care of the environment and human health, the development of alternative eco-friendly methods to inhibit metal corrosion is intensively encouraged. In previous works we showed that some phytocompounds components of essential oils such as carvacrol (Carv) and thymol (TOH) are able to be electropolymerized on metals and they seem to be promissory for this purpose. The aim this paper is to investigate if the biocompatibility of copper covered by coatings formed by electropolymerization of Carv and TOH (polyCarv and polyTOH) is related with the potential selected for the electropolymerization process. Potentiostatic perturbations at different potentials, AFM images, ATR-FTIR spectroscopy and measurements of copper ions release provided suitable information to make a detailed analysis of different stages of the electropolymerization process that leads to polyCarv and polyTOH layers on copper surface. The change of the characteristics of the coatings over time was evaluated after several polymerization periods and current transients were interpreted by using nucleation and growth models. Results showed interesting changes in the polymerization process with the electrochemical perturbation, nature of the isomer, and time of the treatment. The treatment that provides the most protective, transparent and homogeneous layer, that strongly increased the biocompatibility of Cu could be selected: electropolymerization of Carv at 0.4 V. Results highlight the importance of the detailed study of the evolution of the electropolymerization processes to select the best ecofriendly condition due the high impact of potential perturbation and polarization time on the biocompatibility of the resulting polymeric layer-copper system.Facultad de IngenieríaInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Is the biocompatibility of copper with polymerized natural coating dependent on the potential selected for the electropolymerization process?

With the intention of taking care of the environment and human health, the development of alternative eco-friendly methods to inhibit metal corrosion is intensively encouraged. In previous works we showed that some phytocompounds components of essential oils such as carvacrol (Carv) and thymol (TOH) are able to be electropolymerized on metals and they seem to be promissory for this purpose. The aim this paper is to investigate if the biocompatibility of copper covered by coatings formed by electropolymerization of Carv and TOH (polyCarv and polyTOH) is related with the potential selected for the electropolymerization process. Potentiostatic perturbations at different potentials, AFM images, ATR-FTIR spectroscopy and measurements of copper ions release provided suitable information to make a detailed analysis of different stages of the electropolymerization process that leads to polyCarv and polyTOH layers on copper surface. The change of the characteristics of the coatings over time was evaluated after several polymerization periods and current transients were interpreted by using nucleation and growth models. Results showed interesting changes in the polymerization process with the electrochemical perturbation, nature of the isomer, and time of the treatment. The treatment that provides the most protective, transparent and homogeneous layer, that strongly increased the biocompatibility of Cu could be selected: electropolymerization of Carv at 0.4 V. Results highlight the importance of the detailed study of the evolution of the electropolymerization processes to select the best ecofriendly condition due the high impact of potential perturbation and polarization time on the biocompatibility of the resulting polymeric layer-copper system.Facultad de IngenieríaInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Functional nicotinic acetylcholine receptor reconstitution in Au(111)-supported thiolipid monolayers

The insertion and function of the muscle-type nicotinic acetylcholine receptor (nAChR) in Au(111)- supported thiolipid self-assembled monolayers have been studied by atomic force microscopy (AFM), surface plasmon resonance (SPR), and electrochemical techniques. It was possible for the first time to resolve the supramolecular arrangement of the protein spontaneously inserted in a thiolipid monolayer in an aqueous solution. Geometric supramolecular arrays of nAChRs were observed, most commonly in a triangular form compatible with three nAChR dimers of ∼20 nm each. Addition of the full agonist carbamoylcholine activated and opened the nAChR ion channel, as revealed by the increase in capacitance relative to that of the nAChR–thiolipid system under basal conditions. Thus, the self-assembled system appears to be a viable biomimetic model to measure ionic conductance mediated by ion-gated ion channels under different experimental conditions, with potential applications in biotechnology and pharmacology.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Non-enzymatic sensing of carbohydrates using a nickel–chromium alloy electrode

A highly sensitive non-enzymatic carbohydrates sensor based on a nickel hydroxide film on a nickel alloy electrode was developed. The electro-catalytic film is formed by using a potential scan program developed in our research group. This program facilitated the formation of stable proportions of Ni(II)/Ni(III) oxy-hydroxides which are necessary for the electro-catalysis. The structural morphology and roughness of the oxy-hydroxides were characterized by using scanning electron microscopy and atomic force microscopy. The electrochemical behavior of the electrodes in 0.10 M NaOH and in the presence of carbohydrates was characterized by cyclic voltammetry and chronoamperometry, showing good catalytic activity for the anodic oxidation of carbohydrates. Fast and significant amperometric responses were obtained with the renewable nickel hydroxide films, which were easily constructed on the electrodes’ surfaces by potential cycling. The good analytical performance, low cost and straightforward preparation method make this alloy a promising electrode for the development of effective non-enzymatic carbohydrates sensor.Fil: Pissinis, Diego Ezequiel. Universidad Nacional de Cordoba. Facultad de Ciencias Quimicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sereno, Leonides Edmundo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; ArgentinaFil: Marioli, Juan Miguel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Utilization of special potential scan programs for cyclic voltammetric development of different nickel oxide-hydroxide species on Ni based electrodes

Special potential scan programs were designed for cyclic voltammetric development of β-NiOOH or γ-NiOOH/ β-NiOOH mixtures on the surface of nickel or nickel-chromium (80:20) alloy electrodes in NaOH 0.10 M. The programs consisted on changing the anodic or cathodic switching limit to facilitate the chemical reactions taking place either between Ni(II) hydroxides or between Ni(III) oxides-hydroxides. The electrochemical charge density under the oxidative wave, observed at Ni or Ni-Cr electrode surfaces at approximately 0.48 V (vs SCE), remained almost con- stant with the number of cv cycles after approximately 600 cv cycles at 0.050 V/s. Thus, it can be suggested that a stable proportion of Ni(II)/Ni(III) oxides-hydroxides was obtained on the electrode surfaces. The relative amounts of β-NiOOH or γ-NiOOH species were calculated from the electrochemical charges under their reduction waves in the voltammetric experiments. Higher charge densities were always obtained with Ni-Cr alloy electrodes as compared to pure Ni electrodes. Linear relationships were obtained in our study on the dependence of the oxidative peak current with the square root of the scan rate at a scan rate range between 0.01 V/s and 0.16 V/s.Fil: Pissinis, Diego Ezequiel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Sereno, Leonides Edmundo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; ArgentinaFil: Marioli, Juan Miguel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Two-step biocompatible surface functionalization for two-pathway antimicrobial action against Gram-positive bacteria

The use of indwelling devices has emerged as a frequent and often life-saving medical procedure. However, infection in prosthetic surgery is one of the most important and devastating complications. Once the biofilm has been formed, its eradication is extremely difficult, due to an increased resistance to host defense and conventional antimicrobials. Thus, the design of novel strategies for inhibiting the bacterial adhesion on implantable devices is a key point for successful surgical procedures. In this work, the development of a simple two-step protocol to prepare surfaces able to prevent the bacterial growth was successfully achieved. The surface-modification design includes a combined approach involving the multi-functionalization of Ti surfaces with silver nanoparticles (AgNPs) and/or ampicillin (AMP). The surface chemistry involved in AMP adsorption on titanium and silver surfaces was elucidated for the first time, thus establishing the basis for the further anchoring of other antibacterial compounds having similar functional groups. Our results show that the antibiotic binds to the titanium surface through covalent interactions between the –COOH groups in AMP and the –OH groups of the native TiO2 on the surface, although electrostatic interactions between protonated AMP and negatively charged TiO2 can also contribute to the antibiotic anchoring to the surface. The AMP immobilization on the AgNPs is carried out by thiolate-like bonds. The β-lactam ring functionality is preserved after the adsorption process, since the Ti-AgNPs-AMP surface was able to decrease the bacterial viability in more than 80%. Moreover, the antimicrobial capacity is maintained over time due to a two-pathway antibacterial mechanism: death by contact (AMP) and death by release (AgNPs). The effect of AMP prevails on AgNPs at early stages of bacterial adhesion, while AgNPs are responsible for sustaining the relatively low but steady release of Ag(I), preserving the bacteriostatic activity of the surface over time. This effect would contribute to prevent infections due to sessile cells on indwelling devices, powering the action of the immune system and the conventional antibiotics usually dosed in implanted patients.Fil: Pissinis, Diego Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Benitez, Guillermo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Schilardi, Patricia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin