Self-Assembled Monolayer of Monomercaptoundecahydro-closo-dodecaborate on a Polycrystalline Gold Surface.

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2- in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2- in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2-, cyclic voltammetry response of the probe Fe(CN)63-/Fe(CN)64- showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2- diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2- and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode-solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2- were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.

Factores clínicos y epidemiológicos relacionados con la incidencia de sepsis nosocomial en los pacientes ingresados en la Unidad de Neonatología del Hospital de Niños Benjamín Bloom durante el periodo comprendido del 01 de Julio de 2018 al 30 de Julio 2019 / Clinical and epidemiological factors related to the incidence of nosocomial sepsis in patients admitted to the Neonatology Unit of the Benjamin Bloom Children's Hospital during the period from July 1, 2018 to July 30, 2019

La sepsis nosocomial es una entidad clínica que se presenta en todos los hospitales del mundo ocasionando la pérdida de muchas vidas, consumo de medicamentos y elevados costos para su tratamiento, los neonatos son más vulnerables para la adquisición de dicha entidad clínica. Los mecanismos de inmunidad de los recién nacidos son relativamente deficientes en comparación con lactantes y niños mayores, siendo esto de especial relevancia en prematuros y de bajo peso al nacer, en los cuales, la inmadurez del sistema inmune se acompaña de otros factores de riesgo y de procedimientos invasivos que aumentan la vulnerabilidad a infecciones. En el presente trabajo se describen los factores clínicos y epidemiológicos relacionados con la incidencia de sepsis nosocomial en los pacientes ingresados en la unidad de neonatología del hospital de niños Benjamín Bloom.

Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture.

A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule ((Btn)Ab-AgPSA-(HRP)Ab), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population.

Pre-clinical validation study of a miniaturized electrochemical immunoassay based on square wave voltammetry for early detection of carcinoembryonic antigen in human serum.

BACKGROUND: The ELISA format for measuring carcinoembryonic antigen (CEA) serves as a reference standard against which other assays are compared. Because the World Health Organization (WHO) increasingly recommends the use of serum CEA as a diagnostic tool for cancer, it is relevant to explore the reliability of the new decentralized CEA point-of-care-testing (POCT) technologies that are available to physicians and patients, in compliance with mandates of the clinical laboratories' regulatory agencies. METHODS: Electrochemical immunoassay (ECIA) based on trace lead (Pb) analysis by anodic stripping techniques using sandwich-type immunocomplex conjugates: (MB)Ab/AgCEA/Ab(PbS), and a commercial ELISA test system with optical transmission. RESULTS: The ECIA provides better analytical performance than does the ELISA. The within assay precision coefficient of variance (%CVw) of the ECIA is lower than the value recommended by the Hong Kong Association of Medical Laboratories (HKAML), and the recoveries of CEA at 1.0, 5.0, 10.0, 25.0 and 50.0 ng/ml are in the range of 99-110% for control serum samples. The ECIA showed a minimal positive bias of 0.0267 ± 0.3270 ng/ml (P=0.9389). CONCLUSIONS: The proposed CEA screening technology can be practically employed for decentralized clinical analysis of CEA in human serum. Therefore, it can be viewed as a control method for personalized therapy.

Soft purification of N-doped and undoped multi-wall carbon nanotubes.

A soft method for purifying multi-wall carbon nanotubes (N-doped and undoped) is presented. The technique includes a hydrothermal/ultrasonic treatment of the material in conjunction with other subsequent treatments, including the extraction of polyaromatic compounds, dissolution of metal particles, bundle exfoliation, and uniform dispersion. This method avoids harsh oxidation protocols that burn (via thermal treatments) or functionalize (by introducing chemical groups) the nanotubes. We show a careful analysis of each purification step and demonstrate that the technique is extremely efficient when characterizing the materials using scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), scanning tuneling electron microscopy (STEM), x-ray powder diffraction (XRD), diffuse reflectance Fourier transform infrared (DRFTIR) spectroscopy and thermogravimetric analysis (TGA).

Trapping, pattern formation, and ordering of polyelectrolyte/single-wall carbon nanotube complexes at the air/water and air/solid interfaces.

The Langmuir and Langmuir-Blodgett (LB) techniques have been applied in a novel approach to build structurally well-ordered, oriented, and organized assemblies of water-soluble single-wall carbon nanotubes (ws-SWCNTs) at the air/water and air/solid interfaces. The SWCNTs were rendered hydrophilic by complexing them with a quenched polyelectrolyte. We observed that the ws-SWCNT concentration at the air/water interface increases with time condensing into different patterns, among which are isolated soap-froths, rings, and the aggregation of cumuli-like 2D-structures. These patterns were recorded at different compression-expansion stages by Brewster angle microscopy (BAM). From the isotherm measurements, we are able to determine the diffusion process by which ws-SWCNT concentration builds up at the water surface. The corresponding LB films were very stable and could be transferred onto mica substrates easily. Atomic force microscopy (AFM) images revealed that the morphology of these films is surface-pressure dependent, and aligned structures with a nematic-like order formed closely packed mono- or multilayer films. The assembly of 2D-nanostructures by means of this approach offers a great potential for emergent technological applications using modified water-soluble SWCNTs.