Shear-Triggered Release of Lipid Nanoparticles from Tissue-Mimetic Hydrogels.

Shear forces are involved in many cellular processes and increase remarkably in the case of cardiovascular diseases in the human body. While various stimuli, such as temperature, pH, light, and electromagnetic fields, have been considered for on-demand release, developing drug delivery systems that are responsive to physiological-level shear stresses remains as a challenge. For this purpose, liposomes embedded in hydrogel matrices are promising as they can dynamically engage with their environment due to their soft and deformable structure. However, for optimal drug delivery systems, the interaction between liposomes and the surrounding hydrogel matrix, and their response to the shear should be unraveled. Herein, we used unilamellar  1,2-Dimyristoyl-sn-glycero-3phosphocholine (DMPC) liposomes as drug nanocarriers and polyethylene (glycol) diacrylate (PEGDA) hydrogels having different elasticities, from 1 to 180 Pa, as extracellular matrix (ECM)-mimetic matrices to understand shear-triggered liposome discharge from hydrogels. The presence of liposomes provides hydrogels with temperature-controlled water uptake which is sensitive to membrane microviscosity. By systematically applying shear deformation from linear to nonlinear deformation regimes, the liposome release under transient and cyclic stimuli is modulated. Considering that shear force is commonly encountered in biofluid flow, these results will provide fundamental basis for rational design of shear-controlled liposomal drug delivery systems.