Mercado Karla P, Helguera María, Hocking Denise C, Dalecki Diane
1 Department of Biomedical Engineering, University of Rochester , Rochester, New York.
2 Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology , Rochester, New York.
Tissue Eng Part C Methods. 2015 Jul;21(7):671-82. doi: 10.1089/ten.TEC.2014.0527. Epub 2015 Mar 12.
Collagen I is widely used as a natural component of biomaterials for both tissue engineering and regenerative medicine applications. The physical and biological properties of fibrillar collagens are strongly tied to variations in collagen fiber microstructure. The goal of this study was to develop the use of high-frequency quantitative ultrasound to assess collagen microstructure within three-dimensional (3D) hydrogels noninvasively and nondestructively. The integrated backscatter coefficient (IBC) was employed as a quantitative ultrasound parameter to detect, image, and quantify spatial variations in collagen fiber density and diameter. Collagen fiber microstructure was varied by fabricating hydrogels with different collagen concentrations or polymerization temperatures. IBC values were computed from measurements of the backscattered radio-frequency ultrasound signals collected using a single-element transducer (38-MHz center frequency, 13-47 MHz bandwidth). The IBC increased linearly with increasing collagen concentration and decreasing polymerization temperature. Parametric 3D images of the IBC were generated to visualize and quantify regional variations in collagen microstructure throughout the volume of hydrogels fabricated in standard tissue culture plates. IBC parametric images of corresponding cell-embedded collagen gels showed cell accumulation within regions having elevated collagen IBC values. The capability of this ultrasound technique to noninvasively detect and quantify spatial differences in collagen microstructure offers a valuable tool to monitor the structural properties of collagen scaffolds during fabrication, to detect functional differences in collagen microstructure, and to guide fundamental research on the interactions of cells and collagen matrices.
胶原蛋白I作为生物材料的天然成分，在组织工程和再生医学应用中被广泛使用。纤维状胶原蛋白的物理和生物学特性与胶原纤维微观结构的变化密切相关。本研究的目的是开发利用高频定量超声，以非侵入性和无损的方式评估三维（3D）水凝胶中的胶原微观结构。采用积分背向散射系数（IBC）作为定量超声参数，以检测、成像并量化胶原纤维密度和直径的空间变化。通过制备具有不同胶原蛋白浓度或聚合温度的水凝胶来改变胶原纤维微观结构。IBC值是根据使用单元素换能器（中心频率38MHz，带宽13 - 47MHz）收集的背向散射射频超声信号测量计算得出的。IBC随胶原蛋白浓度的增加和聚合温度的降低呈线性增加。生成IBC的参数化3D图像，以可视化和量化在标准组织培养板中制备的水凝胶整个体积内胶原微观结构的区域变化。相应的细胞包埋胶原凝胶的IBC参数图像显示，在胶原蛋白IBC值升高的区域内有细胞聚集。这种超声技术非侵入性地检测和量化胶原微观结构空间差异的能力，为监测胶原支架在制造过程中的结构特性、检测胶原微观结构的功能差异以及指导细胞与胶原基质相互作用的基础研究提供了一种有价值的工具。
