Direct Quantification of Solute Diffusivity in Agarose and Articular Cartilage Using Correlation Spectroscopy

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Biophysics

Background:

• Articular cartilage relies on diffusion for nutrient transport due to its avascular nature.
• Existing methods for quantifying diffusivity in tissues have limitations in invasiveness and spatial resolution.

Purpose of the Study:

• To implement and compare fluorescence correlation spectroscopy (FCS) and raster image correlation spectroscopy (RICS) for direct, minimally invasive quantification of solute diffusion.
• To assess the utility of FCS and RICS in agarose constructs and articular cartilage explants.

Main Methods:

• Quantified diffusion of fluorescein and Alexa Fluor 488-conjugated dextrans (3k, 10k) using FCS and RICS.
• Tested solutes in aqueous solutions, varying concentrations of agarose gels (1%, 3%, 5%), and different zones of juvenile bovine articular cartilage (superficial, middle, deep).
• Evaluated the impact of molecule size, gel concentration, and applied strain on diffusion properties.

Main Results:

• In agarose, solute diffusion decreased with increasing molecule size, gel concentration, and applied strain.
• In articular cartilage, diffusion properties were dependent on solute size, cartilage zone, and compressive strain, consistent with prior research.
• FCS and RICS provided comparable results for solute diffusion quantification.

Conclusions:

• FCS and RICS are effective, simple, and minimally invasive techniques for quantifying microscale solute diffusivity.
• These spectroscopic methods offer a valuable tool for studying transport phenomena in engineered tissues and native cartilage.