Encapsulation and Release of Calcein from Herceptin-conjugated eLiposomes

A Master of Science thesis in Biomedical Engineering by Mah Noor Zafar entitled, “Encapsulation and Release of Calcein from Herceptin-conjugated eLiposomes”, submitted in June 2023. Thesis advisor is Dr. Ghaleb Husseini. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).

Abstract

Cancer is one of the deadliest diseases afflicting humanity with no definitive cure. Its heterogeneous nature poses significant challenges. Currently, available cancer treatments such as; chemotherapy, radiation therapy, surgery, etc., have successfully addressed specific types of cancer. However, their side effects reduce the quality of patient life. Fortunately, new approaches involving triggered site-specific delivery of therapeutic drugs using nanoparticles are being devised to provide a personalized and definitive cure for all types of cancer. Surface modification of liposomes with targeting moieties specific to the receptors on the surface of cancer cells enhances the selectivity of the drug delivery systems and reduces off-target effects. Furthermore, external triggers, such as ultrasound, have surfaced as a promising tool to foster triggered and controlled release of the encapsulated drug. The application of low-frequency ultrasound can induce various mechanical and thermal effects that help disrupt liposomal membranes and trigger the release of encapsulated drugs. This study assessed liposomal encapsulation of sono-sensitive phase-changing perfluoro pentane (PFC5) nanoemulsion droplets alongside Herceptin (Trastuzumab) as a targeting moiety. Four liposomal formulations, namely; NH₂ liposomes, emulsion liposomes (eLiposomes), Herceptin-conjugated liposomes, and Herceptin-conjugated eLiposomes, were synthesized, and characterization tests and assays were conducted throughout the thesis to evaluate the properties of different liposomal-formulations. The size was assessed using dynamic light scattering, whereas the lipid and protein content of the liposomes was assessed using the Stewart and bicinchoninic acid assays, respectively. Low-frequency ultrasound (20kHz) at power densities (6.2, 9, and 10 mW/cm²) was then used to trigger the release of the encapsulated drug from liposomes. Herceptin-conjugated emulsion liposomes showed significantly higher release than the rest of the formulations at all three power densities investigated. Furthermore, the zero-order kinetic model was observed to be the best fit for all the liposomal formulations used in this study. Conjugating an antibody to a nanocarrier encapsulating a chemotherapeutic agent and triggering the latter’s release using ultrasound show promise in the quest for a magic bullet that reduces the side effects of chemotherapy.