Paesen Rik, Sanen Kathleen, Smisdom Nick, Michiels Luc, Ameloot Marcel
Hasselt University, BIOMED, Agoralaan, gebouw C, Diepenbeek 3590, Belgium.
Hasselt University, BIOMED, Agoralaan, gebouw C, Diepenbeek 3590, Belgium.
Acta Biomater. 2014 May;10(5):2036-42. doi: 10.1016/j.actbio.2014.01.011. Epub 2014 Jan 18.
Successful engineering of biomimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from a limited number of straightforward assumptions and by taking into account the P-SHG effect, we were able to cope with the typically observed ACF particularities. Using simulated datasets, the resulting model was thoroughly evaluated and compared with models previously described in the literature. We showed that our new model has no restrictions concerning the fibre length for the density retrieval. For certain length ranges, the model can additionally be used to obtain the average fibre length and the P-SHG related non-zero susceptibility tensor element ratios. From experimental data on collagen type I hydrogels, values of SHG tensor element ratios and fibre thickness were determined which match values reported in the literature, thereby underpinning the validity and applicability of our new model.
仿生组织的成功构建依赖于对所选支架材料力学性能的精确量化。为了改进这种量化方法，典型的体流变学测量通常辅以微观技术，包括无标记二次谐波产生（SHG）成像。图像相关光谱法（ICS）已被用于从纤维支架的SHG图像中获取定量信息。然而，典型的偏振SHG（P-SHG）效应，它部分地定义了自相关函数（ACF）的形状，却从未被考虑在内。在此，我们提出了一种新的灵活模型，以便可靠地将ICS应用于纤维结构的P-SHG图像。通过从有限数量的简单假设出发，并考虑P-SHG效应，我们能够应对通常观察到的ACF特性。使用模拟数据集，对所得模型进行了全面评估，并与文献中先前描述的模型进行了比较。我们表明，我们的新模型在密度反演方面对纤维长度没有限制。对于某些长度范围，该模型还可用于获得平均纤维长度和与P-SHG相关的非零磁化率张量元素比率。从I型胶原水凝胶的实验数据中，确定了SHG张量元素比率和纤维厚度的值，这些值与文献报道的值相符，从而证实了我们新模型的有效性和适用性。
