Figure 2

Sustained release of diffusible signal molecules through microparticles.

(A) (i) The darkfield image of the drug-releasing microparticles (scale bar: 10 μm). (ii) The S.E.M. image of the microparticle cross-section (scale bar: 2 μm). (iii) The brightfield image of a hydrogel matrix containing the microparticles (scale bar: 400 μm). (iv) The phase contrast image of the drug-releasing particles (blue arrows) and hMSC (orange arrows) in a hydrogel matrix (scale bar: 50 μm). (B) Characterization of the microparticles encapsulating the blends of glucose, IGF-1 and albumin. ‘LA: GA ratio’ denotes the composition ratio of lactic acid (LA) units and glycolic acid (GA) units. ‘M.W.’ denotes the molecular weight of each PLGA. Drug encapsulation efficiency is the percentage of the actual amounts of each molecule encapsulated in the microparticles over their theoretical amounts added during the particle preparation. ‘Size’ represents the average diameter of each type of microparticles. (C) The releasing profiles of the three biomolecules from the microparticles. The 1:2 mixtures of 50:50 and 65:35 microparticles (iii) showed relatively continuous releasing rates compared to the individual microparticle types (i and ii) and was used to maintain the concentrations of the released signal molecules in the hydrogel matrices (n = 3).