Rotational Dynamics of Spin-Labeled Polyacid Chain Segments in Polyelectrolyte Complexes Studied by CW EPR Spectroscopy

A nitroxide spin label has been covalently linked to the weak polyacid poly­(ethylene-<i>alt</i>-maleic acid) (P­(E-<i>alt</i>-MA)) to study the rotational mobility of the polyacid backbone in polyelectrolyte complexes (PEC) formed with the oppositely charged strong polycation poly­(diallyldi­methylammonium chloride) (PDADMAC) in dependence on the pH of the dispersion and the temperature. The rotational mobility of the polyacid chain segments has been determined by simulation of the line shape of the continuous wave (CW) electron paramagnetic resonance (EPR) spectra using the microscopic order/macroscopic disorder (MOMD) model of restricted rotational diffusion. The study has shown that the diffusion coefficient characterizing the rotational motions of the polyacid backbone is significantly smaller at low degree of dissociation at pH 4 than at high degree of dissociation at pH 7 and pH 10

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

Descriptive statistics of the repeated quantification (number of repetitions: 20).

<p>Descriptive statistics of the repeated quantification (number of repetitions: 20).</p

Sketch of the bone formation within the circular artificial cleft-like defect over time and the selected slice positions for quantitative MRI and histomorphometry.

<p>With increasing healing time (A… 6 weeks, B… 9 weeks, C… 12 weeks) the content of newly formed bone (<i>BV</i>) rises and grows from the defect margins to the center of the defect. <i>BV</i> analysis has been performed via quantitative MRI (upper row) and histomorphometry (lower row). The slices for MRI analysis were located centrally within the defect, showed a slice thickness (ST) of 200 μm and an interslice distance (iSD) of 250 μm. As a result of the histological preparation of hard tissue the sections had been very thin (ST ~ 30 μm), covered a wide range of the defect size (iSD ~ 1 mm) and also included regions close to the defect margins.</p

Assessing agreement between preclinical magnetic resonance imaging and histology: An evaluation of their image qualities and quantitative results

<div><p>One consequence of demographic change is the increasing demand for biocompatible materials for use in implants and prostheses. This is accompanied by a growing number of experimental animals because the interactions between new biomaterials and its host tissue have to be investigated. To evaluate novel materials and engineered tissues the use of non-destructive imaging modalities have been identified as a strategic priority. This provides the opportunity for studying interactions repeatedly with individual animals, along with the advantages of reduced biological variability and decreased number of laboratory animals. However, histological techniques are still the golden standard in preclinical biomaterial research. The present article demonstrates a detailed method comparison between histology and magnetic resonance imaging. This includes the presentation of their image qualities as well as the detailed statistical analysis for assessing agreement between quantitative measures. Exemplarily, the bony ingrowth of tissue engineered bone substitutes for treatment of a cleft-like maxillary bone defect has been evaluated. By using a graphical concordance analysis the mean difference between MRI results and histomorphometrical measures has been examined. The analysis revealed a slightly but significant bias in the case of the bone volume and a clearly significant deviation for the remaining defect width But the study although showed a considerable effect of the analyzed section position to the quantitative result. It could be proven, that the bias of the data sets was less originated due to the imaging modalities, but mainly on the evaluation of different slice positions. The article demonstrated that method comparisons not always need the use of an independent animal study, additionally.</p></div

MRI images of the skull with different contrasts.

<p>Exemplarily, a specimen of group 2 after six weeks healing time was chosen. The yellow rectangle highlights the region of interest which includes the artificial defect. The arrows indicate the bone substitute material. The scale bars represent 1.0 mm. The repetition time and echo time which have been used for MR imaging (cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.t002" target="_blank">Table 2</a>) were abbreviated with T_R and T_E, respectively. The label description can be also found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.t003" target="_blank">Table 3</a>. (A) Proton density images which showed the best signal-to-noise ratio. They were used for quantitative MRI. (B) T₂ weighted images highlight tissues with high content of unbound water. Adipose tissue appears bright, too. (C) With T₁ weighted images the adipose tissue can be identified.</p

Quantitative results of the bone volume (BV) within the artificial defect.

<p>For comparison, the results of quantitative MRI and histomorphometry of the selected animals for method comparison (cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.t001" target="_blank">Table 1</a>) were presented with the measured <i>BV</i> value of all animals investigated in the study of <i>Korn et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.ref014" target="_blank">14</a>]. The results were displayed as mean ± 95% CI. Statistical significance is indicated by *p< 0.05 and **p<0.01.</p

Experimental design, all of the rats were assigned randomly to the experimental groups.

<p>Experimental design, all of the rats were assigned randomly to the experimental groups.</p

Detectable anatomical tissue structures of coronal slice images [26,27].

<p>Detectable anatomical tissue structures of coronal slice images [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.ref026" target="_blank">26</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.ref027" target="_blank">27</a>].</p

Measured parameters used for the concordance analysis.

<p>Here, a MRI slice image of a control was shown exemplarily. A detailed description of the tissue structures is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.g003" target="_blank">Fig 3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179249#pone.0179249.t003" target="_blank">Table 3</a>. To determine the overall newly formed bone (<i>BV</i>), the bone tissue area at the left and the right side of the artificial defect was measured. The remaining defect width (<i>rDW</i>) is marked with the red arrow. The scale bar represents 1.0 mm.</p