An NMR Study of Biomimetic Fluorapatite - Gelatine Mesocrystals

The mesocrystal system fluoroapatite—gelatine grown by double-diffusion is characterized by hierarchical composite structure on a mesoscale. In the present work we apply solid state NMR to characterize its structure on the molecular level and provide a link between the structural organisation on the mesoscale and atomistic computer simulations. Thus, we find that the individual nanocrystals are composed of crystalline fluorapatite domains covered by a thin boundary apatite-like layer. The latter is in contact with an amorphous layer, which fills the interparticle space. The amorphous layer is comprised of the organic matrix impregnated by isolated phosphate groups, Ca3F motifs and water molecules. Our NMR data provide clear evidence for the existence of precursor complexes in the gelatine phase, which were not involved in the formation of apatite crystals, proving hence theoretical predictions on the structural pre-treatment of gelatine by ion impregnation. The interfacial interactions, which may be described as the glue holding the composite materials together, comprise hydrogen bond interactions with the apatite PO43− groups. The reported results are in a good agreement with molecular dynamics simulations, which address the mechanisms of a growth control by collagen fibers and with experimental observations of an amorphous cover layer in biominerals

Ergebnisse einer retrospektiven Befragung von Bürgerinnen und Bürgern durch das Gesundheitsamt Bautzen zu Symptomen, Krankheitsdauer und Gesundheitsfolgen bei SARS-CoV-2-Infektion

Nach der ersten Welle der COVID-19-Pandemie im Frühjahr 2020 wurde im Landkreis Bautzen eine retrospektive Befragung zu Krankheitsverläufen sowie den gesundheitlichen Folgen einer SARS-CoV-2-Infektion und/oder den Isolations- bzw. Quarantänemaßnahmen durchgeführt. Die vorliegende Arbeit beschreibt die Resultate dieser Befragung und geht der Frage nach, wie gut die gesundheitliche Betreuung durch das Gesundheitsamt Bautzen zu diesem Zeitpunkt eingeschätzt wurde. Dabei wird deutlich, dass im Endemie-/Pandemiefall die Ermittlungstätigkeit im Öffentlichen Gesundheitsdienst einen wesentlichen Beitrag bei der Erhebung und Differenzierung von Krankheitssymptomen leisten kann.Peer Reviewe

Dissolution of artificial otoconia by hydrochloric acid (pH 1) <i>(A,B,C)</i> and details of the dissolution effects (belly-area) <i>(D,E,F)</i>.

<p><i>(A)</i> Intact artificial otoconium before treatment with hydrochloric acid. <i>(B)</i> Dissolution after 15 min and 70 min <i>(C)</i> exposure to hydrochloric acid. The particle in <i>(C)</i> is surrounded by significant amount of organic residue (see red arrow). <i>(D)</i> Surface before exposure. Dissolution after 15 min <i>(E)</i> and 70 min <i>(F)</i> exposure to hydrochloric acid. ESEM, low vacuum (LV), 15 kV. Scale bars in <i>(B)</i> also for <i>(A)</i>: 400 µm, <i>(C)</i>: 100 µm, <i>(D)</i>: 20 µm, <i>(E)</i>: 10 µm and <i>(F)</i>: 5 µm.</p

Inner structure <i>(A)</i> and outer shape <i>(B)</i> of a single human otoconium.

<p><i>(A)</i> 3-D-model of the belly/branch-architecture <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102516#pone.0102516-Walther2" target="_blank">[14]</a>, showing the belly (light-coloured) and the 3+3 branches (dark) meeting at the center of symmetry of the otoconium. The terminal planes representing the end faces of the branches at both sides of the otoconium are turned by 60° to each other. <i>(B)</i> ESEM-image of a single intact human otoconium. High vacuum (HV), 15 kV. Scale bar <i>(B)</i>: 5 µm.</p

Dissolution of artificial otoconia and details of structural changes (belly-area), by treatment with demineralized water.

<p><i>(A)</i> Single artificial otoconium before treatment. Dissolution after 110 hours <i>(B)</i> and 200 hours <i>(F)</i> exposure. The red arrows in <i>(B)</i> and <i>(C)</i> show the position of one of the branches. The blue arrow in <i>(C)</i> points to the belly-area. <i>(D)</i> Surface of the belly-area before exposure and after 110 hours <i>(E)</i> and 200 hours <i>(F)</i> treatment. ESEM, low vacuum (LV), 15 kV. Scale bars <i>(C)</i> also for <i>(A</i>–<i>B)</i>: 300 µm, <i>(D)</i>: 10 µm, <i>(F)</i> also for <i>(E)</i>: 20 µm.</p

Dissolution of artificial otoconia after treatment with EDTA (c = 0,107 mol/L) <i>(A,B,C)</i> and details of the dissolution effects (belly-area) <i>(D,E,F)</i>.

<p><i>(A)</i> Single otoconium before exposure to EDTA. Dissolution after 90 min <i>(B)</i> and 160 min <i>(F)</i> exposure. <i>(D)</i> Surface structure before EDTA treatment and after 30 min <i>(E)</i> and 140 min <i>(F)</i> exposure. The red arrows in <i>(B)</i> and <i>(C)</i> indicate one of the branches of the otoconium. ESEM, low vacuum (LV), 15 kV. Scale bars <i>(A)</i>: 400 µm, <i>(B)</i>: 200 µm, <i>(C)</i>: 100 µm, <i>(D)</i>: 10 µm, <i>(E)</i>: 50 µm, <i>(F)</i>: 20 µm.</p

Intergrowth and Interfacial Structure of Biomimetic Fluorapatite–Gelatin Nanocomposite: A Solid-State NMR Study

The model system fluorapatite–gelatin allows mimicking the formation conditions on a lower level of complexity compared to natural dental and bone tissues. Here, we report on solid-state NMR investigations to examine the structure of fluorapatite–gelatin nanocomposites on a molecular level with particular focus on organic–inorganic interactions. Using ³¹P, ¹⁹F, and ¹H MAS NMR and heteronuclear correlations, we found the nanocomposite to consist of crystalline apatite-like regions (fluorapatite and hydroxyfluorapatite) in close contact with a more dissolved (amorphous) layer containing first motifs of the apatite crystal structure as well as the organic component. A scheme of the intergrowth region in the fluorapatite–gelatin nanocomposite, where mineral domains interact with organic matrix, is presented

Structural Relationship between Calcite-Gelatine Composites and Biogenic (Human) Otoconia

Biogenic otoconia (ear dust) are composite materials of calcite with about 2 wt.-% proteins showing an average longitudinal size of about 10 mu m. The tiny biomineral particles are situated in the inner ear (in the maculae) and act as sensors for gravity and linear acceleration. Our comparative study of calcitegelatine composites (grown by double diffusion) and human otoconia is based on decalcification experiments, scanning electron microscopy, TEM and X-ray investigations in order to obtain a complete picture of the 3D structure and morphogenesis of the materials. Otoconia as calciteprotein composites display a cylindrical body with terminal rhombohedral faces intersecting at the pointed ends. As evidenced by TEM on focused ion beam cuts, both the artificial composites and human otoconia show a particular distribution of areas with different volume densities leading to a dumbbell-shape of the more dense parts consisting of rhombohedral branches (with end faces) and a less ordered, less dense area (the belly region). The peculiar inner architecture of otoconia with its dumbbell-shaped mass/density distribution is assumed to be necessary for optimal sensing of linear accelerations