Fig. 5.

Hydrogels synthesized with dynamic protein units can be used for triggered drug delivery. (A) Calmodulin’s conformational change can trigger hydrogel volume decreases and, in turn, release of drugs from hydrogel microspheres, shown schematically here (from King et al.⁵⁰, copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission). (B) Calmodulin-based microspheres undergo substantial decreases in volume in response to the specific biochemical ligands chlorpromazine (CPZ) and trifluoperazine (TFP). (C) Volume changes can be used to trigger release of growth factors, including vascular endothelial growth factor (VEGF, top) and bone morphogenetic protein-2 (BMP-2, bottom) at T =0 or T =24 h. (D) Growth factor release can also be “pulsed” at multiple times via repeated ligand-induced conformational shifts. The ubiquity of protein conformational changes in nature suggests that these initial demonstrations can potentially be extended to a broad range of specific biochemical “triggers” (reprinted from King et al.⁵¹, with permission from Elsevier).