Dually Heterogeneous Hydrogels via Dynamic and Supramolecular Cross-Links Tuning Discontinuous Spatial Ruptures

Biological tissues are often highly and multiply heterogeneous in both structure and composition, but the integrity of multiheterogeneity in artificial materials is still a big challenge. Herein, dually heterogeneous hydrogels were constructed with two distinct strategies via dynamic bonds and supramolecular cross-links. The hydrogels showed discontinuous spatial ruptures, and the mechanical behaviors of hydrogels could be tuned. The primary heterogeneity resulted from a nonuniform distribution of dynamic and/or static cross-links. The presence of only primary heterogeneity within hydrogels led to uneven mechanical properties that were represented by discontinuous spatial ruptures during the stretching the hydrogel and therefore caused the necking deformation. Further introduction of the secondary heterogeneity by incorporating anisotropic cellulose nanocrystals (CNC) into the hydrogels allowed the adjustment of the necking phenomenon. Moreover, distinct CNC with diverse surface functionalities exhibited different effects: the “active” CNC with surface-attached dynamic bonds retarded the necking propagation, while the “neutral” CNC without further surface modification promoted the extension of necking points. Thus, the regulation of deformation and fracture mode of hydrogels was achieved by the synergy of dually heterogeneous structure

Lengths of untreated and sulfo-SMCC treated MTs at different time points.

<p>The table shows the total number of microtubules (from three independent sets of experiments), average calculated mean length (<i>L</i>_<i>mean</i>) and average mean length from the fitting curve (<i>L</i>_{<i>meanfit</i>}) for sulfo-SMCC treated and untreated MTs, measured after 0 h, 6 h, and 24 h of incubation.</p

Chemically treated and untreated MTs.

<p>The table shows the total numbers of microtubules (from one set of experiments), average calculated mean lengths (<i>L</i>_<i>mean</i>) and average mean lengths from the fitting curve (<i>L</i>_{<i>meanfit</i>}) for untreated MTs, and MTs treated with sulfo-SMCC, maleimide dye, and NHS ester dye for 24 h.</p

Comparison of angular histograms.

<p>Subfigures are as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126346#pone.0126346.g014" target="_blank">Fig 14</a>, now for simulated cells, with all relative masses and distances now linear. Data points corresponding to same methods in plots (a) and (c) are connected only for better visualization.</p

Length distributions of chemically treated and untreated MTs after 24 h of incubation.

<p>Length distributions of 2 mg/ml (tubulin) solution of untreated MTs, MTs treated with 250 <i>μ</i>M sulfo-SMCC, 250 <i>μ</i>M maleimide dye and 250 <i>μ</i>M NHS ester dye are shown. Lengths of MTs are distributed exponentially in all cases; single-exponential fits shown as dashed lines. Treatment with sulfo-SMCC resulted in drastically shorter MTs in comparison to untreated MTs (mean length = 2 <i>μ</i>m and 17 <i>μ</i>m, respectively). Maleimide dye treated MTs, however, showed a less drastic effect with an intermediate mean length of 9.2 <i>μ</i>m. Addition of NHS ester dye to MTs as a control did not affect the lengths of MTs.</p

Tracing results with false positives and missed filaments for an hMSC.

<p>The cell G1 used for this illustration is a fixed cell that has been immunofluorescently stained. The subfigures display: (a) ground truth, (b) FS results, (c) eLoG results, (d) CID results. Green pixels are false positives detected by the method, yellow are correctly identified pixels and red are missed pixels. A pixel is correctly identified, if it corresponds to a ground truth labeled pixel within an 8-neighborhood. A ground truth labeled pixel is considered missing, if no pixel was detected within an 8-neighborhood.</p

Data collected by various methods and comparison of runtime.

<p>Checkmarks in parentheses indicate that for lack of documentation and source code availability the FibreScore method is not portable in terms of full configurability and usability to a generic system.</p><p>Data collected by various methods and comparison of runtime.</p

Illustration of the line Gaussian.

<p>(a) an isotropic two dimensional Gaussian. Convolving the image with such a filter will lead to blurring of the image. (b) restriction of an isotropic Gaussian to a line. This filter locally homogenizes pixel brightness along lines that run in direction of the filter. It is computationally efficient as it only uses few pixels. (c) an elongated Gaussian. This filter also homogenizes lines, but it has much more Pixels and thus requires much longer computation.</p

Flow chart illustrating the algorithm of the line segment sensor.

<p>The algorithm begins at the very top with a binary image and outputs an orientation field and line information, displayed to the bottom left of the chart. A detailed explanation is given in the text.</p

Angular histograms of filament mass for an hMSC.

<p>The cell G1 used for this illustration is a fixed cell that has been immunofluorescently stained. The subfigures display: (a) ground truth, (b) FS results, (c) eLoG results, (d) Hough results. The black curves illustrate the result of kernel smoothing with a Gaussian of standard deviation <i>σ</i> = 10.</p