Concentration profiles within gradient scaffold systems from

Concentration profiles within gradient scaffold systems from a diffusion model simulation. (A) (B) (C) Concentration profiles within the scaffold with PLGA microspheres loaded different doses of PDGF-BB (2, 20, 200 ng for A, B and C, respectively) predicted from a diffusion model. The color bar is in units of ng ml^-1 and is constant for all images. Insets show concentration distributions at high scale. All systems result in the same profile shape but different magnitude. Location (z = 0) is the distal-gradient layer of the scaffold and distance (z = 4 mm) is the scaffold-tissue - interface. Magnitude of the gradient for all cases (1, 10 and 100 ugml^-1) at the tissue interface. The inset shows 2 and 20 ng cases at a higher scale. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Solution

The color bar to the right of the plot shows the color that has been used to represent the concentration. The scaffold contains different doses of PDGF-BB within PLGA microspheres. The growth factor (PDGF) will gradually diffuse out of the microspheres throughout the scaffold. Over a period of time, the growth factor will come to exist in a concentration gradient, with highest concentrations in the core of the scaffold and gradually decreasing as a function of distance from the center. The graphs depict this information. On any point of time, the concentration of the growth factor at a particular distance within the scaffold has been plotted. The three graphs (A-C) compare the concentration gradients that develop over time when three different doses of the growth factor were loaded within the PLGA microspheres.