Xu Zhengbin, Ozcelikkale Altug, Kim Young L, Han Bumsoo
Weldon School of Biomedical Engineering, Purdue University , West Lafayette, IN 47907.
J Nanotechnol Eng Med. 2013 Feb;4(1):110051-110059. doi: 10.1115/1.4024130. Epub 2013 Jul 11.
Quality and functionality of engineered tissues are closely related to the microstructures and integrity of their extracellular matrix (ECM). However, currently available methods for characterizing ECM structures are often labor-intensive, destructive, and limited to a small fraction of the total area. These methods are also inappropriate for assessing temporal variations in ECM structures. In this study, to overcome these limitations and challenges, we propose an elastic light scattering approach to spatiotemporally assess ECM microstructures in a relatively large area in a nondestructive manner. To demonstrate its feasibility, we analyze spectroscopic imaging data obtained from acellular collagen scaffolds and dermal equivalents as model ECM structures. For spatial characterization, acellular scaffolds are examined after a freeze/thaw process mimicking a cryopreservation procedure to quantify freezing-induced structural changes in the collagen matrix. We further analyze spatial and temporal changes in ECM structures during cell-driven compaction in dermal equivalents. The results show that spectral dependence of light elastically backscattered from engineered tissue is sensitively associated with alterations in ECM microstructures. In particular, a spectral decay rate over the wavelength can serve as an indicator for the pore size changes in ECM structures, which are at nanometer scale. A decrease in the spectral decay rate suggests enlarged pore sizes of ECM structures. The combination of this approach with a whole-field imaging platform further allows visualization of spatial heterogeneity of EMC microstructures in engineered tissues. This demonstrates the feasibility of the proposed method that nano- and micrometer scale alteration of the ECM structure can be detected and visualized at a whole-field level. Thus, we envision that this spectroscopic imaging approach could potentially serve as an effective characterization tool to nondestructively, accurately, and rapidly quantify ECM microstructures in engineered tissue in a large area.
工程组织的质量和功能与其细胞外基质（ECM）的微观结构和完整性密切相关。然而，目前可用的表征ECM结构的方法通常劳动强度大、具有破坏性，并且仅限于总面积的一小部分。这些方法也不适用于评估ECM结构的时间变化。在本研究中，为了克服这些限制和挑战，我们提出了一种弹性光散射方法，以无损方式在相对较大的区域对ECM微观结构进行时空评估。为了证明其可行性，我们分析了从脱细胞胶原支架和真皮替代物作为模型ECM结构获得的光谱成像数据。对于空间表征，在模拟冷冻保存程序的冻融过程后检查脱细胞支架，以量化胶原基质中冷冻诱导的结构变化。我们进一步分析了真皮替代物中细胞驱动压实过程中ECM结构的空间和时间变化。结果表明，从工程组织弹性反向散射的光的光谱依赖性与ECM微观结构的变化敏感相关。特别是，波长上的光谱衰减率可以作为ECM结构中纳米级孔径变化的指标。光谱衰减率的降低表明ECM结构的孔径增大。这种方法与全场成像平台的结合进一步允许可视化工程组织中EMC微观结构的空间异质性。这证明了所提出方法的可行性，即可以在全场水平上检测和可视化ECM结构的纳米和微米级变化。因此，我们设想这种光谱成像方法有可能成为一种有效的表征工具，以无损、准确和快速地量化大面积工程组织中的ECM微观结构。
