Effect of Microbubble Incorporation on Local Solute Transport in Tissue Engineered Cartilage Constructs

Previously, microbubbles have been studied for a number of different medical applications including ultrasound imaging contrast and drug delivery [1]. Microbubbles are comprised of a gas enclosed in a lipid shell. Recent research has shown that the inclusion of microbubbles in tissue engineered cartilage constructs has been shown to enhance mechanical and biochemical growth [2,3]. This modification of the tissue engineering scaffold by incorporation of gas-filled microbubbles has been shown to homogenize depth-dependent mechanical properties (Fig. 1) [3], which, in standard constructs, resembles a “U-shaped” strain profile with the stiffest regions on the edges surrounding a soft center [4]. In addition, these microbubble containing constructs are described by a higher partition coefficient than standard constructs, indicating increased solute transport [3]. These results led us to propose the hypothesis that the incorporation of microbubbles: a) increases nutrient transport upon microbubble dissolution, b) creates fluid-filled pores upon gas efflux and subsequent influx of culture media [3]. In this study, the aforementioned hypothesis is interrogated through analysis of local solute diffusivity.