Characterization of anisotropic diffusion tensor of solute in tissue by video-FRAP imaging technique

In this study, a new method for determination of an anisotropic diffusion tensor by a single fluorescence recovery after photobleaching (FRAP) experiment was developed. The method was based on two independent analyses of video-FRAP images: the fast Fourier transform and the Karhunen-Loève transform. Computer-simulated FRAP tests were used to evaluate the sensitivity of the method to experimental parameters, such as the initial size of the bleached spot, the choice of the frequencies used in the Fourier analysis, the orientation of the diffusion tensor, and experimental noise. The new method was also experimentally validated by determining the anisotropic diffusion tensor of fluorescein (332 Da) in bovine annulus fibrosus. The results obtained were in agreement with those reported in a previous study. Finally, the method was used to characterize fluorescein diffusion in bovine meniscus. Our findings indicate that fluorescein diffusion in bovine meniscus is anisotropic. This study provides a new tool for the determination of anisotropic diffusion tensor that could be used to investigate the correlation between the structure of biological tissues and their transport properties.