Department of Mechanical and Manufacturing Engineering, The University of Calgary, Calgary, Canada.
Human Performance Laboratory, The University of Calgary, Calgary, Canada.
Biomech Model Mechanobiol. 2020 Dec;19(6):2397-2412. doi: 10.1007/s10237-020-01346-z. Epub 2020 Jun 19.
Fluorescence recovery after photobleaching (FRAP) is a widely used technique for studying diffusion in biological tissues. Most of the existing approaches for the analysis of FRAP experiments assume isotropic diffusion, while only a few account for anisotropic diffusion. In fibrous tissues, such as articular cartilage, tendons and ligaments, diffusion, the main mechanism for molecular transport, is anisotropic and depends on the fibre alignment. In this work, we solve the general diffusion equation governing a FRAP test, assuming an anisotropic diffusivity tensor and using a general initial condition for the case of an elliptical (thereby including the case of a circular) bleaching profile. We introduce a closed-form solution in the spatial coordinates, which can be applied directly to FRAP tests to extract the diffusivity tensor. We validate the approach by measuring the diffusivity tensor of [Formula: see text] FITC-Dextran in porcine medial collateral ligaments. The measured diffusion anisotropy was [Formula: see text] (SE), which is in agreement with that reported in the literature. The limitations of the approach, such as the size of the bleached region and the intensity of the bleaching, are studied using COMSOL simulations.
荧光漂白后恢复（FRAP）是一种广泛用于研究生物组织中扩散的技术。大多数现有的 FRAP 实验分析方法都假设各向同性扩散，而只有少数方法考虑各向异性扩散。在纤维组织中，如关节软骨、肌腱和韧带，扩散是分子运输的主要机制，具有各向异性，并取决于纤维的排列。在这项工作中，我们针对 FRAP 测试，假设各向异性扩散张量，并针对椭圆（从而包括圆）漂白轮廓的一般初始条件，求解控制 FRAP 测试的一般扩散方程。我们在空间坐标中引入了一个封闭形式的解，可直接应用于 FRAP 测试以提取扩散张量。我们通过测量[Formula: see text] FITC-Dextran 在猪内侧副韧带中的扩散张量来验证该方法。测量的扩散各向异性为[Formula: see text]（SE），与文献报道的一致。还使用 COMSOL 模拟研究了该方法的限制，如漂白区域的大小和漂白的强度。
