A fortified lipid bilayer platform for improved drug packaging and therapeutic delivery - Liposome, composed of a lipid bilayer comprising phospholipids (PL) and sterols such as cholesterol (Chol), has been extensively used for packaging and delivery of therapeutic agents due to its intrinsic biocompatibility and biodegradability. While most approved liposomal nanotherapeutics can improve pharmacokinetics (PK) and reduce systemic toxicities, improvements in therapeutic efficacy and overall survival are disappointing, underscoring the urgent need for enhanced therapeutic delivery. Chol plays a critical role in fortifying membrane packing and reducing bilayer fluidity and permeability by promoting the liquid condensed state in lipid membranes, enhancing bilayer rigidity and strength. Lipid bilayers with high levels of Chol are generally more stable than those without or with less Chol. However, under the physiological environment, Chol is rapidly extracted from the bilayer by biomembranes and serum proteins, which jeopardizes bilayer stability and results in premature content leakage, fast blood clearance and unwanted adverse effects, leading to suboptimal clinic efficacy. In addition, although enhanced permeability and retention effect allows nanotherapeutic accumulation to the periphery of diseased tissues, intracellular internalization and tissue penetration remain inefficient due to the tenacious resistance imposed by high interstitial fluid pressure and dense extracellular matrix, compromising the therapeutic outcome. These phenomena present formidable barriers for lipid bilayer-based therapeutic delivery. To tackle these key challenges, the overall vision of my research program is to establish a stabilized lipid bilayer with improved physicochemical properties that can further improve drug delivery and selectively fortify intracellular uptake and infiltration at target sites. We have established a Chol-derived PL via covalently attaching Chol to a PL with varied stimuli-responsive linkages. Via systemic structure activity relationship studies, we demonstrated that Chol-derived PL blocked Chol transfer, prevented payload leakage, prolonged circulation time, and augmented efficacy in treating lung inflammation, Alzheimer’s disease, lymphoma, pancreatic and triple negative breast cancer models, which were linker chemistry dependent. For the next five years, the goals of this proposal are to 1) unravel the underlying mechanisms and principles on how the structural alterations of a sterol-modified PL bilayer that forms liposome but cannot shuttle between biomembranes will affect drug and gene delivery via substituting Chol with other membrane sterols; and 2) establish a universal ultra pH-sensitive charge-reversal delivery platform to boost the cellular uptake and tissue penetration efficiency via incorporating an intelligent build-in cationization mechanism that selectively triggers effective adsorption-mediated endocytosis and transcytosis at diseased tissues. Completing these studies will provide fundamental and functional correlations of bilayer properties with therapeutic delivery, enable us to establish a set of design rules governing the optimal interactions between lipid bilayer and encased drugs, and provide a paradigm-shifting toolbox to advance the drug delivery technologies, facilitating clinical translation of treating human diseases.
