Effect of Dynamic Deformational Loading on the Transport of Dextran Molecules Into Agarose Gels

The poor intrinsic healing capacity of articular cartilage has led to a number of attempts to engineer a replacement tissue [1]. One of these approaches, termed functional tissue engineering, suggests that the application of mechanical preconditioning, mimicking the in vivo loading environment, may enhance the development of material properties in these constructs [2,3]. Using this approach, our previous studies have demonstrated that dynamic loading (DL) increases the mechanical properties of chondrocyte-seeded agarose hydrogels relative to free swelling (FS) controls [4–6]. One mechanism by which the increase in mechanical properties occurs is hypothesized to be due to enhanced transport of nutrients and/or growth factors under dynamic loading [7]. The goal of the current study is to determine the effect of dynamic loading on the transport of neutral dextran molecules into agarose gels. Dextran, a neutral and generally inert solute commonly used in diffusion and transport studies, is used in its fluorophore-conjugated form thus making it possible to track the solute and quantify its content inside a hydrogel. We hypothesize that the uptake of dextran molecules into the agarose gels will be significantly enhanced under the influence of physiological dynamic deformation loading. Two varying molecular weights of dextran, 3 kDa and 70 kDa, were chosen in this study to ascertain a wide range of transport behaviors, and to interpret the experimental results in the context of a recently developed mixture theory model for the transport of neutral solutes in a neutrally charged gel, such as agarose [8].