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