A General Approach to Enzyme-Responsive Liposomes.

Liposomes are effective nanocarriers due to their ability to deliver encapsulated drugs to diseased cells. Nevertheless, liposome delivery would be improved by enhancing the ability to control the release of contents at the target site. While various stimuli have been explored for triggering liposome release, enzymes provide excellent targets due to their common overexpression in diseased cells. We present a general approach to enzyme-responsive liposomes exploiting targets that are commonly aberrant in disease, including esterases, phosphatases, and β-galactosidases. Responsive lipids correlating with each enzyme family were designed and synthesized bearing an enzyme substrate moiety attached via a self-immolating linker to a non-bilayer lipid scaffold, such that enzymatic hydrolysis triggers lipid decomposition to disrupt membrane integrity and release contents. Liposome dye leakage assays demonstrated that each enzyme-responsive liposome yielded significant content release upon enzymatic treatment compared to minimal release in controls. Results also showed that fine-tuning liposome composition was critical for controlling release. DLS analysis showed particle size increases in the cases of esterase- and β-galactosidase-responsive lipids, supporting alterations to membrane properties. These results showcase an effective modular strategy that can be tailored to target different enzymes, providing a promising new avenue for advancing liposomal drug delivery.