High resolution x-ray imaging of dynamic solute transport in cyclically deformed porous tissue scaffolds

The objective was to develop a method for high-resolution imaging of dynamic solute transport in cyclically deforming porous scaffolds for tissue engineering applications. A flexible cubic scaffold with single cylindrical channel was fabricated from a biodegradable polymer blend using a combined 3D printing and injection molding technique. The scaffold was attached to the bottom of a fluid reservoir mounted underneath a compression apparatus placed inside the X-ray scanner. The scaffold was positioned with the channel axis perpendicular to the X-ray beam. The container was filled with glycerin, and a solution of the contrast agent sodium iodide (NaI) in glycerin was injected into the scaffold channel. Intervals of compression cycles (14.5 ± 2.1 % compression at 1.0 Hz) were applied to the top face of the scaffold. After each interval the compression was temporarily paused to obtain a two-dimensional image at 20 μm pixel resolution. A series of images was also obtained without application of the compression cycles to quantify the effect of passive diffusional removal of NaI from the channel. The average NaI concentration in the channel decreased by 82% after 300 cycles (5 min.) of compression, by 40% after 60 min. of passive removal. Spatial profiles of the NaI concentration along the channel axis indicated that compression-induced transport preferentially removed the contrast agent at the pore openings. We conclude that convective transport induced by cyclic mechanical deformation of artificial tissue scaffolds could significantly contribute to the rate and depth of nutrient transport inside the scaffold, as compared to slow diffusive transport alone.