Lateral flow immunoassays provide low cost, fast, portable and simple to use devices, with yes/no answers seen by the naked eye, that has found applications in agriculture, biomedicine, the ...environment, and food industries. Making these quantitative, via electrochemical or optical approaches, is the present day challenge, with a vision that one day, these will be connected to smartphone technologies, which exhibit a promising digital platform for point‐of‐care diagnostics, mobile healthcare and bioanalytical needs. These devices are fully automated and equipped with a high resolution camera, a powerful processor with high storage capacity, wireless connectivity, real‐time geo‐tagging, secure data management, and cloud computing.
Silicon oxycarbides modified with main group or transition metals (SiMOC) are usually synthesized via pyrolysis of sol‐gel precursors from suitable metal‐modified orthosilicates or polysiloxanes. In ...this study, the phase composition of different SiMOC systems (M = Sn, Fe, Mn, V, and Lu) was investigated. Depending on the metal, different ceramic phases formed. For M = Mn and Lu, MOx/SiOC ceramic nanocomposites were formed, whereas other compositions revealed the formation of M/SiOC (M = Sn), MSix/SiOC (M = Fe) or MCx/SiOC (M = V) upon pyrolysis. The different phase compositions of the SiMOC materials are rationalized by a simple thermodynamic approach which generally correctly predicts which type of ceramic nanocomposite is expected upon ceramization of the metal‐modified precursors. Calculations show that the thermodynamic stability of the MOx phase with respect to that of the C–O system is the most important factor to predict phase formation in polymer‐derived SiMOC ceramic systems. A secondary factor is the relative stability of metal oxides, silicates, carbides, and silicides.
Within this study, the oxidation behavior of SiHfBCN ceramic powders and monoliths was studied at temperatures from 1200 to 1400°C. Both powder and monolithic samples exhibited parabolic oxidation ...behavior characterized by very low rates (10−9–10−8mg2cm−4h−1). The activation energy of 112.9kJmol−1, which was determined for the SiHfBCN powder, is comparable to that of other silica formers such as silicon or SiC and relates to the diffusion of molecular oxygen through silica scale. Whereas, the values determined for the SiHfBCN ceramic monoliths (174 and 140kJmol−1, depending on the Hf content) indicate the complex nature of their oxidation process, leading at temperatures below 1300°C to a continuous oxide scale consisting of borosilicate, silica, m-and t-HfO2. At higher temperatures, the oxide scale consists of silica, HfSiO4 as well as m-and t-HfO2 and becomes discontinuous, probably due to the evaporation of boria.
Novel amorphous polymer-derived Si–Hf–N ceramics were prepared via ammonolysis of single-source precursors which were synthesized by the chemical reaction of a commercially available ...perhydropolysilazane (PHPS) with different amounts of tetrakis(dimethylamido) hafnium(IV) (TDMAH). The prepared Si–Hf–N materials were annealed in nitrogen atmosphere at different temperatures ranging from 1100°C to 1800°C and investigated with respect to their chemical composition, crystallization behavior and phase evolution. The single-source precursors converted upon heat treatment in ammonia environment at 1000°C into amorphous single-phase ceramics and remained amorphous even after annealing at 1400°C in nitrogen atmosphere. Electron microscopy investigation showed that the annealing of the highly homogeneous single-phase Si–Hf–N induces local enrichment (clustering) of Hf, leading to amorphous HfN/SiNx nanocomposites. Annealing in nitrogen at 1600°C leads to the crystallization of HfN and Si3N4. The results of the present work emphasize a convenient preparative access to silicon–metal–nitride nanocomposites from suitable single-source precursors.
Nanocomposites comprise polysilazane-derived SiCN ceramic charged with carbon nanotubes (CNTs) have been prepared by dispersion of multi-walled CNTs with a diameter of 80 nm in a cross-linked ...polysilazane (HTT 1800, Clariant) using a simple roll-mixer method. Subsequently, the composites were warm pressed and pyrolyzed in argon atmosphere. Scanning electron microscopy (SEM) and 3D Raman imaging techniques were used as major tools to assess the dispersion of CNTs throughout the ceramic matrix. Furthermore, studies on the effect of the volume fraction of CNTs in the nanocomposites on their electrical properties have been performed. The specific bulk conductivities of the materials were analyzed by AC impedance spectroscopy, revealing percolation thresholds (ρ
c
) at CNT loadings lower than 1 vol%. Maximum conductivity amounted to 7.6 × 10
−2
S/cm was observed at 5 vol% CNT. The conductivity exponent in the SiCN/CNT composites was found equal to 1.71, indicating transport in three dimensions.
Protease Amperometric Sensor Ionescu, Rodica E.; Cosnier, Serge; Marks, Robert S.
Analytical chemistry (Washington),
09/2006, Letnik:
78, Številka:
18
Journal Article
Recenzirano
An amperometric biosensor for the detection of trypsin was developed. The latter was based on a two-layer configuration, namely, a polymer−glucose oxidase inner layer and a gelatin outer layer. In ...the presence of glucose, the enzyme layer produces H2O2 and hence an amperometric signal due to H2O2 electrooxidation was generated by potentiostating the electrode at 0.6 V. The biosensor detects the change in the increase in the maximum current caused by the proteolytic digestion of gelatin, which covers the platinum electrodes, thereby facilitating a speedier access for the glucose substrate to the electrode modified with both poly(pyrrole−alkylammonium) and glucose oxidase molecules. Our biosensor detected low trypsin concentrations down to 42 pM with a response time of ∼10 min, making it a very sensitive device in the detection of lower trypsin levels with such future putative applications as the diagnosis of pancreatic diseases.
An Electrochemical Lateral Flow Immunosensor (ELFI) is developed combining screen-printed gold electrodes (SPGE) enabling quantification together with the convenience of a lateral flow test strip. A ...cellulose glassy fiber paper conjugate pad retains the marker immunoelectroactive nanobeads which will bind to the target analyte of interest. The specific immunorecognition event continues to occur along the lateral flow bed until reaching the SPGE-capture antibodies at the end of the cellulosic lateral flow strip. The rationale of the immunoassay consists in the analyte antigen NS1 protein being captured selectively and specifically by the dengue NS1 antibody conjugated onto the immunonanobeads thus forming an immunocomplex. With the aid of a running buffer, the immunocomplexes flow and reach the immuno-conjugated electrode surface and form specific sandwich-type detection due to specific, molecular recognition, while unbound beads move along past the electrodes. The successful sandwich immunocomplex formation is then recorded electrochemically. Specific detection of NS1 is translated into an electrochemical signal contributed by a redox label present on the bead-immobilized detection dengue NS1 antibody while a proportional increase of faradic current is observed with increase in analyte NS1 protein concentration. The first generation ELFI prototype is simply assembled in a cassette and successfully demonstrates wide linear range over a concentration range of 1–25ng/mL with an ultrasensitive detection limit of 0.5ng/mL for the qualitative and quantitative detection of analyte dengue NS1 protein.
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•Described the development of an electrochemical immunosensor for dengue NS1 protein.•Affordable, portable, compact and simple to operate.•Combining screen-printed electrodes with the convenience of a lateral flow test strip.•Quantitative detection of dengue NS1 protein.•Good detection capability.
Enlarged vestibular aqueduct (EVA) is a common finding in tomodensitometry. When cranial MRI is performed, enlarged endolymphatic sac (EES) can also be found. Profound hearing loss is a common ...finding in these patients but a few studies have investigated vestibular function after cochlear implantation (CI) in EVA and EES patients. Our main objective was to find out whether in EVA children candidates to CI, a higher endolymphatic sac (ES) volume was predictive for higher rates of postsurgical vestibular complications.
We retrospectively included EVA children who benefited from CI, during the last 2 years. Two groups were constituted according to the presence or not of a vestibular impairment (decrease in the VOR gain on the VHIT test on one of the semicircular canals and/or a loss of cVEMPs) 6 months after CI. Endolymphatic volume of both VA and ES was measured for each patient.
Fifteen patients were included. The mean endolymph volume was significantly higher in the impaired group (0.40 cm3 ± 0.23, range 0.08–0.70) than in the non-impaired group (0.11 cm3 ± 0.07, range 0.04–0.29; p = 0.029). Four children of the impaired group were followed during one year. At the end of vestibular rehabilitation, all children recovered a lateral canal function and a saccular function.
In EVA children, a combined EES appears to increase the risk of severe post CI vestibular impairment. To minimize this risk prior CI surgery, besides tomodensitometry, MRI measurement of the ES volume should be systematically performed.
Cryptococcus spp. is a fungus responsible for 600,000 deaths per year worldwide, mainly in immunosuppressed subjects. However, 20% of cases occur in immunocompetent subjects. Neuropathic disorders ...involving the auditory nerve have been reported, but vestibular disorders have never been described in detail. We report the case of an immunocompetent man, who presented audiovestibular disorders leading to a diagnosis of cryptococcal meningitis.
A 39-year-old man was referred for balance disorders and right sensorineural hearing loss. He presented right vestibulo-saccular impairment and bilateral absence of auditory brainstem responses. Brain MRI was suggestive of cryptococcal meningitis. A cystic lesion in the right flocculus compressed the vestibulocochlear nerve. During monthly follow-up, pure tone audiometry gradually improved and speech audiometry in silence returned to normal. Partial resynchronization of the auditory afferent pathways was observed only on the contralateral side to vestibulocochlear nerve compression, while complete recovery of saccular function was observed.
Cryptococcal meningitis in immunocompetent subjects may be accompanied by lesions of the auditory and vestibular afferent pathways. Recovery of hearing and balance was observed in response to medical treatment and early vestibular rehabilitation.
In the context of the SARS-CoV-2 pandemic, patients may have been dissuaded from seeking consultation, thus exposing themselves to a risk of loss of chance. This guide aims to define how ...teleconsultation can assist in assessing vertiginous adults or children, and to gather the information needed to provide quick medical care.
These recommendations rely on the authors’ experience as well as on literature. A survey on otoneurologic approach via telemedicine has been conducted based on a literature search until March 2020.
The first clinical assessment of the vertiginous patient via teleconsultation can only be successful if the following conditions are met: initial contact to verify the feasibility of the assessment at a distance, the presence of a caregiver in order to assist the patient, the possibility of making video recordings. Medical history via telemedicine, as in a face-to-face assessment, allows to assess the characteristics, duration, frequency, and potential triggering factors of the vertigo, in both children and adults. During teleconsultation, the following tests can be carried out: oculomotricity evaluation, assessment of balance, simple neurological tests, checking for positional vertigo/nystagmus and, eventually to perform canalith-repositioning procedures. In children, the following should be searched for: history of hearing or visual impairment, a context of fever or trauma, otorrhea, signs of meningeal irritation.
The neurotologic telemedicine relies on the accuracy of the clinical assessment, which is based on history taking and a few simple tests, encouraging the development of a decision-making algorithm adapted for teleconsultation. However, the latter has its limitations during an emergency examination of a new patient presenting vertigo, and, at least in some cases, cannot replace a face-to-face consultation. Teleconsultation is often adapted for follow-up consultations of previously selected vertiginous patients during face-to-face assessment.
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