An in Vitro Investigation on Polymeric-Core Lipid Nano-carriers’ Transport across Biological Barriers and Use for Delivery of Cancer Therapeutics

Delivery of therapeutic and diagnostic compounds to specific sites in the body often faces several challenges. Among these challenges are crossing the obstacles created by biological barriers, such as the blood-brain barrier (BBB) and lymphatic endothelial layer, cell selectivity and efficient uptake, and retaining activity. In recent decades, nanoparticles (NPs) particularly those composed of biocompatible materials such as lipids and polymers have shown the ability to overcome these hurdles to some extent and have thus, become attractive candidates for delivery purposes in various medical applications. To date, several intrinsic physicochemical properties of NPs, such as size and surface charge, have proven to be critical in modulating NPs’ bio-distribution including their transport across biological barriers. Recent studies have suggested that NP bio-distribution is also affected by NP mechanical properties including rigidity. Such effect may in part be due to the impact of NP’s rigidity on crossing the above-mentioned barriers in the body. Centered around this hypothesis, the first part of this thesis investigates the influence of NPs’ rigidity on their ability to cross BBB and lymphatic endothelium in vitro. This part further examines the impact of NP rigidity on their interactions with brain tumor cells, for the first time.

To this end, we first optimized an in vitro BBB trans-well model by evaluating several culture conditions individually and in combination, characterized by trans-endothelial electric resistance (TEER), tight junction protein expression, and barrier permeability. NPs with different elastic moduli were then prepared and evaluated for their transport across the optimized BBB model, using a new approach that relied on nanoparticle tracking analysis (NTA). We also assessed the uptake of these NPs by human glioblastoma U87 cells, as a model target. Next, we investigated the impact of rigidity on NPs traveling through the initial lymphatics under physiological conditions in vitro. These transport studies were conducted using an in vitro lymphatic endothelium trans-well model that we developed under either static or dynamic conditions. The influence of the particle elasticity along with the particle size was investigated.

The second part of this thesis focuses on development and assessment of a nano-carrier for delivery of a potent cancer therapeutic, di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), to enable its safe and targeted delivery to cancerous cells. To this end, we applied NPs of poly(lactic-co-glycolic acid) (PLGA) modified with either lipids or PVA (polyvinyl alcohol) to encapsulate DpC and characterized the resultant NP for size, charge, stability, encapsulation efficiency and release of DpC. Finally, the cytotoxicity of these DpC-loaded NPs were studied in three different cancer cell lines of human glioblastoma (U87), breast cancer (MCF7), and colorectal cancer cells (HT29).