BIOPHYSICAL CHEMISTRY OF LIPOSOME-PROTEIN INTERACTIONS: BIOMEDICAL APPLICATIONS

Candidate: Sarah McColman
Supervisor: Dr. David Cramb

ABSTRACT

The growing field of nanomedicine is leading to improvements in bioimaging, therapeutics, diagnostics, and fundamental biomedical research. Studying interactions between nanoparticles and other entities found in biological systems is essential to apply such particles safely and effectively to biomedicine. In this dissertation, three manuscripts describe studies of biomedically relevant interactions involving liposome nanoparticles. First, liposomes were applied as a platform to present antigens through the creation of protein-reconstituted liposome virus-like particles. SARS-CoV-2 Spike Glycoproteins were successfully reconstituted into multicomponent liposomes designed to mimic a viral envelope membrane. Evidence of cellular uptake into relevant lung epithelial cells was presented, and colocalization between the spike protein and its natural receptor, ACE-2, suggested the possibility of binding between these entities which would support the use of this ACE-2 mediated internalization pathway. The complex methods in the first study led to a fundamental investigation of detergent saturation of liposomes. This second study offered insight into how detergent saturation temperature during detergent-mediated protein reconstitution can influence the product of such processes. Saturation temperature did not notably change the results of the protein reconstitution process, except when that temperature exceeded the cloud point of the detergent being used in which case large aggregates were formed. Techniques were presented that will improve methodology and analysis of protein reconstitution protocols. The final study elucidated fundamental drivers of the serum protein binding partly responsible for protein corona formation in vivo, a major challenge preventing successful application of liposome-based biomedicine. Along with data from experiments performed on other nanoparticle systems, this study presents a theory where “hotspots” of local charge and fluidity drive – and limit – interactions between albumin proteins and nanoparticles. This study suggested that different nanoparticles, including various types of liposomes, should not be considered to equally interact with soluble proteins. Generally, interactions between these nanoparticles and biologically relevant molecules such as detergents and proteins should be carefully considered based on nanoparticle chemical differences to understand and develop these systems for use in fundamental and applied biomedical science.