Knowledge of solute transport in biological tissues is fundamental in order to understand cell nutrition and biosynthetic activity, and to design and fabricate tissue engineered constructs. It is believed that diffusion is a major transport mechanism for solutes in avascular tissues. In particular, for tissues characterized by a structural anisotropic morphology (e.g., intervertebral disc, menisci, ligaments), diffusive transport may be anisotropic [1-3]. In addition, some solutes (e.g., growth factors, cationic solutes) can reversibly bind to the extracellular matrix (ECM) of tissues [4-7]. It has been reported that binding interactions significantly slow solute diffusion [7]. Therefore, knowledge of solute diffusive-reactive properties is crucial in order to characterize molecular transport in biological tissues. Recently, several fluorescence recovery after photobleaching (FRAP) methods have been proposed for the analysis of solute diffusive-reactive transport in living cells (e.g., [8]). These techniques are able to quantitatively determine both diffusivity and binding rates. However, their use is limited to the case of isotropic diffusion.
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