Dynamic nuclear polarization of spherical nanoparticles

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Spherical silica nanoparticles of various particle sizes (∼10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e.g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size. We determined an approximate DNP penetration-depth (∼4.2 or ∼5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI).DFG, GRK 1524, Self-Assembled Soft-Matter Nanostructures at Interface

Herstellung und Charakterisierung von Poly((2-Dimethylamino)Ethyl Methacrylat) (PDMAEMA) gepfropften Silica-Nanopartikeln (SNPs)

In this work, we described a multi-step route for preparation of a pH responsive polymer, 2-(dimethylamino) ethyl methacrylate (DMAEMA), grafted silica nanoparticles with a size of 10- 100 nm in diameter via surface initiated- atom transfer radical polymerization (SI-ATRP). We prepare as a starting point well-defined silica nanoparticles (SNPs) by means of amino acid-based catalysis (L-Arginine) or ammonia from precursors like tetraethoxysilane (TEOS), which allows to achieve monodisperse SNPs in the size range of 10- 400 nm. The resulting silica nanoparticles (SNP) were treated with 3-aminopropyl triethoxysilane (APS), a silane coupling agent; yielding primary amino group onto silica surface and followed by immobilization of initiator, α-bromoisobutyryl bromide (BIBB), in order to initiate the ATRP of DMAEMA. In the next step they become polymerically modified whereas monomer we employ 2-(dimethylamino) ethyl methacrylate (DMAEMA) by Atomic Transfer Radical Polymerization (ATRP) because this allows good control over the target molecular weight (and its distribution) of the grafted polymers. The main challenge for this study was to synthesize well-defined polymer grafted silica nanoparticles with controlled molecular weight and low polydispersity. To better compare and understand the polymerization process, we have done a systematic investigation and characterization on each surface modification steps based on the factors as follows: (1) synthesis highly dispersed uniform sized silica nanoparticles in various size (2) solvent effect on each polymerization steps, (3) effect of DMAEMA content on polymerization step, (4) controllable ATRP of DMAEMA onto surface of nanoparticles with different core size. The physicochemical properties of the resulting polymer-grafted silica nanoparticles were characterized by thermogravimetric analysis (TGA), dynamic/static light scattering (DLS/SLS), transmission or scanning electron microscopy (TEM/ SEM) and Fourier transform infrared spectroscopy (FTIR). Zeta potential (ZP) measurements were also performed in order to study interactions between silica nanoparticles and DMAEMA polymeric shell in response to changes of pH. The morphology, size (shell thickness) and dispersibility of DMAEMA grafted SNPs in solvents were examined after each modification steps in terms of surface modification, size and shape, and stability, and compared with unmodified SNPs.In dieser Arbeit haben wir einen mehrstufigen Weg zur Herstellung von pH-responsiven Polymer, 2-(Dimethylamino)ethylmethacrylat (DMAEMA) gepfropften Silica-Nanopartikeln (SNPs) mit einer Größe von 10 bis 100 nm Durchmesser durch radikalisch initierte Atom Transfer Radikal polymerisation beschrieben (SI-ATRP). Ausgehend von Aminosäure-basierten Katalysen (L-Arginin) oder Ammoniak aus Vorläufern wie Tetraethoxysilan (TEOS) bereiten wir klar definierte SNPs als Ausgangspunkt vor, wodurch monodisperse SNPs im Größenbereich von 10-400 nm entstehen. Die erhaltenen SNPs wurden mit 3-Aminopropyl-triethoxysilan (APS), einem Silan-Haftvermittler, behandelt was eine primäre Aminogruppe auf der Siliciumdioxidoberfläche erhält, anschließend erfolgt die Immobilisierung des Initiators α-Bromisobutyrylbromid (BIBB), um die Atom Transfer Radikal Polymerisation (ATRP) von DMAEMA zu initiieren. Im nächsten Schritt werden sie polymerisiert, wobei das Monomer 2- (Dimethylamino)ethyl methacrylat (DMAEMA) durch ATRP verwendet wird. Dies ermöglicht eine gute Kontrolle des Zielmolekulargewichts (und seiner Verteilung) der gepfropften Polymere. Die Hauptherausforderung für diese Studie bestand darin, gut definierte, mit Polymeren gepfropfte SNPs mit kontrolliertem Molekulargewicht und niedriger Polydispersität zu synthetisieren. Um den Polymerisationsprozess besser vergleichen und verstehen zu können, haben wir eine systematische Untersuchung und Charakterisierung der einzelnen Oberflächen-modifikationsschritte durchgeführt, basierend auf den folgenden Faktoren: (1) Synthese hochdisperser SNPs mit einheitlicher Größe in verschiedenen Größen (2) Wirkung des Lösungsmittels bei jeder Polymerisation (3) Wirkung des DMAEMA-Gehalts auf den Polymerisationsschritt, (4) kontrollierbare ATRP von DMAEMA auf die Oberfläche von Nanopartikeln mit unterschiedlicher Partikelgröße. Die physikalisch-chemischen Eigenschaften der erhaltenen polymergepfropften SNPs wurden durch thermogravimetrische Analyse (TGA), dynamisch/ statische Lichtstreuung (DLS/ SLS), Transmissions- oder Rasterelektronenmikroskopie (TEM/ SEM) und Fourier-Transformations-Infrarotspektroskopie (FTIR) charakterisiert. Zeta-Potentialmessungen (ZP) wurden ebenfalls durchgeführt, um Wechselwirkungen zwischen Silica Nanopartikeln und der polymeren DMAEMA-Hülle als Reaktion auf Änderungen des pH-Werts zu untersuchen. Die Morphologie, Größe (Schalendicke) und Dispergierbarkeit von DMAEMA-gepfropften SNPs in Lösungsmitteln wurden nach jedem Modifikationsschritt hinsichtlich Oberflächenmodifikation, Größe und Form und Stabilität untersucht und mit nicht modifizierten SNPs verglichen

Olfactory and Gustatory Dysfunctions in COVID-19 Patients

The prevalence of sensory disorders (smell and/or taste) in affected patients has shown a high variability of 5% to 98% during the COVID-19 outbreak, depending on the methodology, country, and study. Loss of smell and taste occurring in COVID-19 cases are now recognized by the international scientific community as being among the main symptoms of the disease. This study investigates loss of smell and taste in outpatients and hospitalized patients with laboratory-confirmed COVID-19 infection. METHODS: Enrolled in the study were patients with a positive PCR test for COVID-19. Excluded were patients with chronic rhinosinusitis, nasal polyposis, common cold, influenza, and olfactory/gustatory dysfunction predating the pandemic. Patients were asked about changes in their sense of smell and taste by structured questionnaire. Their status was classified according to severity of the symptoms. RESULTS: A total of 217 patients were included in the study, of whom 129 received outpatient treatment, whereas 88 were hospitalized; mean age was 41.74 years (range18–76), 59.4% were male. At evaluation for olfactory dysfunction, 53.9% of the patients were found to be normal, whereas 33.2% were anosmic. No gustatory dysfunction was found in 49.8% of patients, whereas in those with loss of taste, the most commonly recorded symptom was ageusia. Anosmia was significantly more common in outpatients (P = 0.038). Presentation of chemosensorial symptoms in women was higher than in men (P = 0.009). No correlation was found between olfactory and gustatory dysfunction and age (P = 0.178). CONCLUSIONS: About one-half of our patients presented olfactory and/or gustatory deficits, and loss of smell was more common in mild cases. It should be considered; a sudden, severe, and isolated loss of smell and/or taste may also be present in COVID-19 patients who are otherwise asymptomatic. We suggest that identification of persons with these signs and early isolation could prevent spread of the disease in the community

The effect of microporous vanadosilicate AM-6 thin films as photocatalysts for the degradation of methylene blue

In the current study, a new photocatalyst in thin film form exhibiting photocatalytic activity under visible light range was introduced. For that purpose, microporous vanadosilicate (AM-6, (Na,K)(2)VSi5O13) and silver nanoparticle (Ag-0) incorporated vanadosilicate AM-6 thin films were investigated as photocatalysts for the photocatalytic decomposition of methylene blue (MB). To create different oxidation states of vanadium cation present in the center dot center dot center dot V-o-V-o-V center dot center dot center dot quantum wires within the framework of AM-6, two different molar compositions were used for thin film formation of vanadosilicate AM-6. The vanadosilicate AM-6 thin films demonstrated photocatalytic activity under ultraviolet (UV) and visible light irradiation. The microporous titanosilicate (ETS-10, (Na.K)(2)TiSi5O13) thin films, isomorph of vanadosilicate AM-6, were also used as photocatalysts for the degradation of MB for the comparison of photocatalytic effectiveness. When visible light irradiation is used for the photocatalytic decomposition of MB, the photocatalytic activity of AM-6 was significantly different with respect to ETS-10. The narrower band gap of AM-6 with respect to the band gap of ETS-10 and the presence of V5+ cations in the structure of AM-6 provided photocatalytic activity under visible light irradiation. It was found that, vanadosilicate AM-6 films with higher amount of V5+ ions possess better photocatalytic activity under visible light irradiation for the degradation of MB, which can be attributed to the presence of V5+ cations within the framework of AM-6. The presence of both V4+ and V5+ cations was characterized by XPS and Raman spectroscopy in the vanadosilicate AM-6 thin films. To enhance the photocatalytic activity of AM 6 thin films, Na+ and K+ ions of the as-synthesized AM-6 thin films were ion-exchanged with Ag+ ions and then reduced to Ag-0 nanoparticles (NP) by using sodium borohydride (NaBH4) solution. The results showed that Ag-0 NP incorporated AM-6 thin films showed an increased photocatalytic activity due to various reasons such as the role of metal nanoparticles as electron traps, surface plasmon resonance effect, and band-gap narrowing

Mutations in TMC1 contribute significantly to nonsyndromic autosomal recessive sensorineural hearing loss: a report of five novel mutations

Genome wide homozygosity mapping using Affymetrix 10K arrays revealed the DFNB7/11 locus including the TMC1 gene in 5 of 35 Turkish families with autosomal recessive nonsyndromic severe to profound congenital or prelingual-onset sensorineural hearing loss (SNHL). Additional 51 families were later screened for co-segregation of the locus with the phenotype using microsatellite markers. GJB2 and mtDNA A1555G mutations were negative in probands from each family. Mutation analysis was performed in families showing co-segregation of autosomal recessive SNHL with haplotypes at the DFNB7/11 locus. A total of six different mutations in seven families were identified, including novel missense alterations, p.G444R (c.1330G>A), p.R445C (c.1333C>T), and p.I677T (c.2030T>C), one novel splice site mutation IVS6+2 T>A (c.64+2T>A), and a novel large deletion of approximately 31kb at the 3' region of the gene including exons 19-24, as well as a previously reported nonsense mutation, p.R34X (c.100C>T). All identified mutations co-segregated with autosomal recessive SNHL in all families and were not found in Turkish hearing controls. These results expand the mutation spectrum of TMC1 with five novel mutations and provide data for the significant contribution of TMC1 mutations in hearing loss

Existence of SARS-CoV-2 RNA on ambient particulate matter samples: A nationwide study in Turkey

Coronavirus disease 2019 (COVID-19) is caused by the SARS-CoV-2 virus and has been affecting the world since the end of 2019. The disease led to significant mortality and morbidity in Turkey, since the first case was reported on March 11th, 2020. Studies suggest a positive association between air pollution and SARS-CoV-2 infection. The aim of the present study was to investigate the role of ambient particulate matters (PM), as potential carriers for SARS-CoV-2. Ambient PM samples in various size ranges were collected from 13 sites including urban and urban-background locations and hospital gardens in 10 cities across Turkey between 13th of May and 14th of June 2020 to investigate the possible presence of SARS-CoV-2 RNA on ambient PM. A total of 203 daily samples (TSP, n = 80; PM2.5, n = 33; PM2.5-10, n = 23: PM10 mu m, n = 19; and 6 size segregated PM, n = 48) were collected using various samplers. The N1 gene and RdRP gene expressions were analyzed for the presence of SARS-CoV-2, as suggested by the Centers for Disease Control and Prevention (CDC). According to real time (RT)-PCR and three-dimensional (3D) digital (d) PCR analysis, dual RdRP and NI gene positivity were detected in 20 (9.8%) samples. Ambient PM-bound SARS-CoV-2 was analyzed quantitatively and the air concentrations of the virus ranged from 0.1 copies/m(3) to 23 copies/m(3). The highest percentages of virus detection on PM samples were from hospital gardens in Tekirdag, Zonguldak, and Istanbul, especially in PM2.5 mode. Findings of this study have suggested that SARS-CoV-2 may be transported by ambient partides, especially at sites close to the infection hot-spots. However. whether this has an impact on the spread of the virus infection remains to be determined. (C) 2021 Elsevier B.V. All rights reserved

Post-discharge mortality in the first wave of COVID-19 in Turkey

© 2022 Asian Pacific Journal of Tropical Medicine.Objective: To determine post-discharge mortality and associated factors of the first-wave multicenter Turkish Thoracic Society (TTD)-TURCOVID study. Methods: In this retrospective cohort study, we analyzed the data of 18 of 26 centers included in the first TTD-TURCOVID study, and 1 112 cases diagnosed with COVID-19 between 11 March and 31 July 2020 participated in the study. All causes of death after COVID-19 discharge were recorded. Results: The mean age of the patients was (51.07±16.93) years, with 57.6% male patients. In the cohort group, 89.1% of COVID-19 treatment locations were hospital wards, 3.6% were intensive care units (ICUs), and 7.2% were community outpatients. In the longterm follow-up, the in-hospital mortality rate was 3.6% (95% CI 2.64.8), the post-discharge mortality rate was 2.8% (95% CI 1.9-3.9), and the total mortality was 6.3% (95% CI 5.0-7.8). After discharge, 63.3% of mortality overall occurred during the first six months. Mortality rates in post-discharge follow-ups were 12.7% (95% CI 8.0-30.6) in cancer patients, 10.8% (95% CI 6.3-22.9) in chronic obstructive pulmonary disease patients, 11.1% (95% CI 4.4-22.7) in heart failure patients, 7.8 (95% CI 3.8-14.3) in atherosclerotic heart disease patients, and 2.3% (95% CI 0.8-5.6) in diabetes mellitus patients. In smokers/ex-smokers, the all-mortality rates were higher than in non-smokers. Conclusions: This multicenter study showed that patients over 65 years of age, males, former/active smoker, ICU stay, lung, heart disease, and malignancy should be followed up for at least the first six months after discharge due to COVID-19