A silicon carbide nanowire field effect transistor for DNA detection.

This work reports on the label-free electrical detection of DNA molecules for the first time, using silicon carbide (SiC) as a novel material for the realization of nanowire field effect transistors (NWFETs). SiC is a promising semiconductor for this application due to its specific characteristics such as chemical inertness and biocompatibility. Non-intentionally n-doped SiC NWs are first grown using a bottom-up vapor-liquid-solid (VLS) mechanism, leading to the NWs exhibiting needle-shaped morphology, with a length of approximately 2 µm and a diameter ranging from 25 to 60 nm. Then, the SiC NWFETs are fabricated and functionalized with DNA molecule probes via covalent coupling using an amino-terminated organosilane. The drain current versus drain voltage (I d-V d) characteristics obtained after the DNA grafting and hybridization are reported from the comparative and simultaneous measurements carried out on the SiC NWFETs, used either as sensors or references. As a representative result, the current of the sensor is lowered by 22% after probe DNA grafting and by 7% after target DNA hybridization, while the current of the reference does not vary by more than ±0.6%. The current decrease confirms the field effect induced by the negative charges of the DNA molecules. Moreover, the selectivity, reproducibility, reversibility and stability of the studied devices are emphasized by de-hybridization, non-complementary hybridization and re-hybridization experiments. This first proof of concept opens the way for future developments using SiC-NW-based sensors.

Bio-functionalization of silicon carbide nanostructures for SiC nanowire-based sensors realization.

The bio-functionalization process consisting in grafting desoxyribo nucleic acid via aminopropyl-triethoxysilane is performed on several kinds of silicon carbide nanostructures. Prior, the organic layer is characterized on planar surface with fluorescence microscopy and X-ray photoelectron spectroscopy. Then, the functionalization is performed on two kinds of nanopillar arrays. One is composed of top-down SiC nanopillars with a wide pitch of 5 microm while the other one is a dense array (pitch: 200 nm) of core-shell Si-SiC nanowires obtained by carburization of silicon nanowires. Depending on both the pillar morphology and the pitch, different results in term of DNA surface coverages are obtained, as seen from fluorescence microscopy images. Particularly, in the case of the wide pitch array, it has been shown that the DNA molecules are located all along the nanopillars. To achieve a DNA sensor based on a nanowire-field effect transistor, the functionalization must be conducted on a single SiC nanowire or nanopillar that constitutes the channel of the field effect transistor. The localization of the functionalization in a small area around the nanostructures guarantees high performances to the sensor. In this aim, the functionalization process is combined with common microelectronics techniques of lithography and lift-off. The DNA immobilization is investigated by fluorescence microscopy and atomic force microscopy.

Carburization of Si microwires by chemical vapour deposition.

We report the elaboration of silicon carbide (SiC) nanostructures thanks to the carburization of silicon microwires (MWs) under methane at high temperature. The produced SiC nanostructures display a tubular shape and are polycrystalline. The as-prepared silicon carbide microtubes (MTs) were characterized and studied by scanning electron microscopy (SEM), dual focused ion beam-scanning electron microscope (FIB-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The formation of microtubes can be explained by the out-diffusion of Si through the SiC during the carburization process.

Utilización de levetiracetam intravenoso en un hospital general / The Use of intravenous levetiracetam in a general hospital

Introducción y objetivos. Aunque la vía oral es la forma habitual de administración de los fármacos antiepilépticos, en ciertas ocasiones se requiere la vía parenteral. El levetiracetam es el único de los nuevos fármacos antiepilépticos con posibilidad de administración por vía intravenosa. Se presenta un estudio de utilización de levetiracetam intravenoso en un hospital general, con evaluación de su eficacia y seguridad. Pacientes y métodos. Se analizaron de forma retrospectiva las historias clínicas de todos los pacientes ingresados en el hospital que fueron tratados con levetiracetam intravenoso durante el período de tiempo comprendido entre julio de 2007 y mayo de 2008. Resultados. Un total de 53 pacientes fue tratado con levetiracetam intravenoso. Aproximadamente la mitad de los pacientes (47%) había estado ingresada a cargo del servicio de neurología, seguido del servicio de neurocirugía (21%) y oncología (9%). La edad media fue de 52,2 años (rango: 9-87 años) y el 40% eran mujeres. Las crisis fueron sintomáticas en el 81%, y las etiologías más frecuentes fueron los ictus (40%) y los tumores cerebrales (33%). La presentación clínica más frecuente fueron las crisis epilépticas repetidas (47,2%) y el estado epiléptico (26,4%). Globalmente, el control de las crisis se consiguió en el 87% de los pacientes. No se detectaron efectos adversos graves atribuibles al tratamiento con levetiracetam. Conclusiones. El levetiracetam intravenoso parece ser un fármaco antiepiléptico eficaz y seguro en pacientes hospitalizados, especialmente en aquéllos que presentan comorbilidad asociada y/o plurimedicación (AU)

Introduction and aims. Although antiepileptic drugs are usually administered orally, sometimes they must be given intravenously. Levetiracetam is the only one of the new antiepileptic drugs that can be administered intravenously. In this study we report on the use of intravenous levetiracetam in a general hospital, while also evaluating its effectiveness and safety. Patients and methods. A retrospective analysis was conducted of the medical records of all hospital admissions that were treated with intravenous levetiracetam between July 2007 and May 2008. Results. A total of 53 patients were treated with intravenous levetiracetam. Approximately half the patients (47%) had been admitted to neurology, followed by neurosurgery (21%) and oncology (9%). The mean age was 52.2 years (range: 9-87 years) and 40% were females. Seizures were symptomatic in 81% of cases and the most common aetiologies were strokes (40%) and brain tumours (33%). The most frequent presenting symptoms were repeated epileptic seizures (47.2%) and epileptic status (26.4%). Overall, control of seizures was achieved in 87% of patients. No severe side-effects that could be attributed to levetiracetam therapy were detected. Conclusions. Intravenous levetiracetam seems to be an effective, safe antiepileptic drug in hospitalised patients, and especially so in those who present an associated comorbidity and/or who are on multiple drug therapy (AU)

[The use of intravenous levetiracetam in a general hospital]. / Utilización de levetiracetam intravenoso en un hospital general.

INTRODUCTION AND AIMS: Although antiepileptic drugs are usually administered orally, sometimes they must be given intravenously. Levetiracetam is the only one of the new antiepileptic drugs that can be administered intravenously. In this study we report on the use of intravenous levetiracetam in a general hospital, while also evaluating its effectiveness and safety. PATIENTS AND METHODS: A retrospective analysis was conducted of the medical records of all hospital admissions that were treated with intravenous levetiracetam between July 2007 and May 2008. RESULTS: A total of 53 patients were treated with intravenous levetiracetam. Approximately half the patients (47%) had been admitted to neurology, followed by neurosurgery (21%) and oncology (9%). The mean age was 52.2 years (range: 9-87 years) and 40% were females. Seizures were symptomatic in 81% of cases and the most common aetiologies were strokes (40%) and brain tumours (33%). The most frequent presenting symptoms were repeated epileptic seizures (47.2%) and epileptic status (26.4%). Overall, control of seizures was achieved in 87% of patients. No severe side-effects that could be attributed to levetiracetam therapy were detected. CONCLUSIONS: Intravenous levetiracetam seems to be an effective, safe antiepileptic drug in hospitalised patients, and especially so in those who present an associated comorbidity and/or who are on multiple drug therapy.

Phonon- and surface-roughness-limited mobility of gate-all-around 3C-SiC and Si nanowire FETs.

We present numerical simulations of gate-all-around (GAA) 3C-SiC and Si nanowire (NW) field effect transistors (FETs) using a full quantum self-consistent Poisson-Schrödinger algorithm within the non-equilibrium Green's function (NEGF) formalism. A direct comparison between Si and 3C-SiC device performances sheds some light on the different transport properties of the two materials. Effective mobility extraction has been performed in a linear transport regime and both phonon- (PH) and surface-roughness-(SR) limited mobility values were computed. 3C-SiC FETs present stronger acoustic phonon scattering, due to a larger deformation potential, resulting in lower phonon-limited mobility values. Although Si NW devices reveal a slightly better electrostatic control compared to 3C-SiC ones, SR-limited mobility shows a slower degradation with increasing charge density for 3C-SiC devices. This implies that the difference between Si and 3C-SiC device mobility is reduced at large gate voltages. 3C-SiC nanowires, besides their advantages compared to silicon ones, present electrical transport properties that are comparable to the Si case.