Direct quantification of solute diffusivity in strained porous, viscoelastic materials using correlation spectroscopy
Date
2016
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Publisher
University of Delaware
Abstract
Articular cartilage is an avascular tissue, and as such, diffusive transport is important in cartilage homeostasis and disease. While numerous techniques have been used to quantify diffusivity within porous, hydrated tissues, and to assess both cartilage pathology and the maturity of tissue engineered constructs, to date, these techniques have suffered from limitations in terms of their invasiveness and spatial resolution. In the present study, we implemented and compared two separate correlation spectroscopy techniques, fluorescence correlation spectroscopy (FCS) and raster image correlation spectroscopy (RICS), for quantifying fluorescent solute diffusion in agarose and articular cartilage. Specifically, we observed the equilibrium diffusion of fluorescein isothiocyanate (FITC), and Alexa Fluor 488-conjugated 3K and 10K dextrans in aqueous solutions, agarose gels of varying concentration (1%, 3%, 5%), and in different zones of juvenile bovine articular cartilage explants (i.e. superficial, middle, and deep). In agarose, diffusion coefficients were inversely related to the size of the molecule and agarose gel concentration. In cartilage, no statistically significant trends were observed; however, the diffusion coefficient values obtained via FCS and RICS were in agreement with previously published work, using other techniques. Thus, this study demonstrated the utility of FCS and RICS as simple and minimally invasive ways to quantify solute diffusivity within both agarose constructs and bovine articular cartilage explants.