Shima Akar

Topic

Microfluidic Liposome-Based Encapsulation of Avobenzone and Octyl Methoxycinnamate for Enhanced UV Protection

Department of Mechanical Engineering

Date & location

• Friday, September 11, 2026

• 9:00 A.M.

• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Mina Hoorfar, Department of Mechanical Engineering, University of Victoria (Supervisor)

• Dr. Mohsen Akbari, Department of Mechanical Engineering, UVic (Member)

• Dr. Katherine Elvira, Department of Chemistry, UVic (Outside Member) 

External Examiner

• Dr. Razieh Salahandish, Department of Electrical Engineering and Computer Science, York University 

Chair of Oral Examination

• Dr. Abdul Vahabpour Roudsari, School of Health Information Science, UVic 

Abstract

Organic UV filters such as avobenzone (AVO) and octyl methoxycinnamate (OMC) are widely used for broad-spectrum UVA and UVB protection but face challenges including photodegradation, formulation instability, penetration beyond the stratum corneum, and concentration-dependent cytotoxicity. These limitations highlight the need for delivery systems that improve UV-filter stability, safety, and localization at the skin surface. Liposomes, biocompatible phospholipid-based vesicles, provide a protective microenvironment that can reduce premature degradation, limits direct interaction with skin components, and enhances formulation compatibility. However, their application in advanced sunscreen formulations remains limited, particularly in systems requiring reproducible nanoscale fabrication and scalable manufacturing.

A key factor governing liposome performance is lipid membrane rigidity, which influences vesicle stability, permeability, and retention behavior. Membrane properties can be tailored through cholesterol incorporation in low-transition-temperature lipid systems or through the use of inherently high-transition-temperature lipids that form more ordered and less permeable bilayers. This thesis investigates these complementary lipid design strategies for AVO and OMC encapsulation while addressing the fabrication challenges associated with high-transition-temperature systems. To overcome limitations of conventional liposome fabrication methods, including poor control over particle characteristics, batch-to-batch variability, and limited scalability, microfluidic platforms were developed for the reproducible synthesis of PEGylated liposomes. These platforms were subsequently applied to engineer UV-filter-loaded formulations and evaluate their potential to improve the stability, performance, and safety of chemical UV filters.

This thesis comprises three manuscript-based studies. The first study developed a microfluidic platform for PEGylated liposome synthesis using low-transition-temperature lipids (egg yolk phosphatidylcholine, EYPC). A computational fluid dynamics (CFD) model (OpenFOAM) was used to optimize micromixing and device design, enabling the production of liposomes with tunable sizes (~60–150 nm), low polydispersity (PDI < 0.2), and efficient encapsulation of surrogate hydrophobic cargo, Nile red. The second study extended the platform to DSPC, a high-transition-temperature lipid, by integrating temperature control above its phase-transition temperature. This approach enabled controlled DSPC liposome production with efficient UV-filter incorporation, confirmed bilayer organization, and concentration-dependent cytocompatibility in fibroblast and keratinocyte models. Final study applies the optimised low-transition lipid platform to co-encapsulate AVO and OMC. The resulting liposomes exhibited spherical nanoscale morphology, mean sizes of approximately 150 nm, low polydispersity (~0.1), moderately negative surface charge, and encapsulation efficiencies of up to 90%. Compared with free UV filters, the liposomal formulations showed up to ~50% reduction in photodegradation, up to sixfold reduction in dermal penetration, and improved cytocompatibility in fibroblast and keratinocyte cell lines. Photostability evaluation was enabled by a custom-designed UV solar simulator developed in this work, providing controlled and reproducible irradiation conditions.

Overall, this thesis establishes a microfluidic framework for producing liposomes with tunable physicochemical properties and efficient encapsulation of hydrophobic compounds, advancing their application in nanomedicine and nanocosmetics. The developed liposomal UV-filter formulations demonstrate improved photostability, reduced dermal penetration, and enhanced cytocompatibility, highlighting their potential to overcome key limitations of conventional chemical sunscreens and support the development of next-generation photoprotective systems.