DESIGN AND DEVELOPMENT OF PATCHY LIPOSOMES AS POTENTIAL DELIVERY CARRIERS WITH ENHANCED FUSOGENICITY OR BINDING ABILITY

Nanoliposomes are one of the most commonly used delivery nanocarriers due to their biocompatibility, biodegradability, and low toxicity. To achieve high levels of cellular uptake, liposomes often require large doses of fusion-promoting molecules or targeting ligands that can lead to undesired side effects, including toxicity and immunogenicity. To address this challenge, this project aims to utilize the biological process of membrane phase-separation to design and develop liposomes that can offer highly efficient cellular internalization with minimal toxicity. First part of this dissertation combines experimental and computational tools to investigate the phase behavior of multi-component lipid membranes. The experimental studies focused on studying phase-separation on micron-sized liposomes of various compositions using fluorescence microscopy. In collaboration with mathematicians, two continuum phase-field models were then developed to simulate the phase-separation examined in experiments. Great agreement between experiments and simulations validated the computational models and demonstrated their potential use for the design of phase-separating and patchy liposomes.
Second part of this dissertation explores the use of phase-separation to create highly fusogenic liposomal nanocarriers with minimal toxicity. The impact of charged lipids on membrane’s phase behavior was first investigated in multi-component micron-sized liposomes. The findings of this work were then applied towards designing fusogenitic liposomes with cationic patches that showed enhanced fusogenicity compared to their homogenous counterparts. This work demonstrated that phase-separation can be applied to enhance the performance of cationic delivery liposomes. The last part of this dissertation seeks to use phase-separation to enhance cellular uptake of ligand-conjugated liposomes. Focusing on biotin-streptavidin binding, as a model system, biotinylated liposomes were designed to respond to acidic pH in tumor environment to undergo phase-separation and present their ligands in highly-dense patches. We are further investigating the application in cell studies. Together, this study provides an insight into the use of phase-separation to control the functionality of lipid membranes and it hence, offers new possibilities to overcome the shortcomings of current liposomal nanocarriers.