Fluorescence recovery after photobleaching: direct measurement of diffusion anisotropy
- PDF / 5,332,140 Bytes
- 16 Pages / 595.276 x 790.866 pts Page_size
- 51 Downloads / 217 Views
ORIGINAL PAPER
Fluorescence recovery after photobleaching: direct measurement of diffusion anisotropy Kotaybah Hashlamoun1,2,3 · Ziad Abusara2,5 · Ariel Ramírez‑Torres4 · Alfio Grillo4 · Walter Herzog1,2 · Salvatore Federico1,2 Received: 29 October 2019 / Accepted: 12 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 3 kDa FITC-Dextran in porcine medial collateral ligaments. The measured diffusion anisotropy was 1.42 ± 0.015 (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. Keywords FRAP · Anisotropic diffusion · Fibrous tissues · Ligaments · Direct measure
1 Introduction Molecular diffusion is the process by which chemical species, e.g. solutes or macromolecules, move from regions of higher concentration to regions of lower concentration. Diffusion plays a vital role in cellular functions, such as protein–protein interactions and metabolism (Verkman 2002). * Salvatore Federico [email protected] 1
Department of Mechanical and Manufacturing Engineering, The University of Calgary, Calgary, Canada
2
Human Performance Laboratory, The University of Calgary, Calgary, Canada
3
Graduate Programme in Biomedical Engineering, The University of Calgary, Calgary, Canada
4
Department of Mathematical Sciences “G.L. Lagrange”, ‘Dipartimento di Eccellenza 2018‑2022’, Politecnico di Torino, Torino, Italy
5
Present Address: Advanced Imaging and Histopathology Core, Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. Box 34110, Doha, Qatar
In porous connective tissues such as ligaments and cartilage, diffusion is one of the primary mechanisms for nutrient transport. For this reason, it has been extensively studied in healthy and degraded tissues (Maroudas 1968; BurtonWurster and Lust 1990; Xia et al. 1994, 1995; Leddy and Guilak 2003; Leddy et al. 2006). Several techniques can be used for measuring self or molecular diffusivity (or diffusion coefficient in the isotropic case) of s
Data Loading...
