Mechanical stimulation triggered growth factor release: A) Release rate of VEGF from alginate hydrogels under 10% (open circle) and 25% (open squares) strain amplitude, and with no compression (filled circles) as a control. In vivo response to VEGF-loaded hydrogels implanted into femoral artery ligation site: B) without mechanical stimulation, and C) with mechanical stimulation, D) Schematic of anticipated drug release from polymeric matrices under mechanical loading: open circle, free drug; filled circle, bound drug. In vitro release behaviors of trypan blue (triangle), methylene blue (square), and VEGF (circle) from alginate hydrogels under mechanical stimulus: E) in vitro release rate, and F) Cumulative release. Reproduced with permission [169,170].