PROJECT SUMMARY/ABSTRACT The objective of the proposed research is to engineer a targeted biological nanoparticle platform with high intracranial delivery and glial cell targeting for broad applicability in drug delivery and imaging. A great deal of work has already been accomplished elucidating the ability of certain extracellular vesicles (EVs) to cross endothelial barriers, especially the blood-brain barrier (BBB). Other work has established that EVs exhibit excellent tropism towards particular tissues and cell types. The focus of this proposal is to understand the mechanisms by which certain EV subpopulations accomplish these feats, and to engineer them into a hybrid liposome-EV drug delivery platform. Given the plethora of recent research into EV structure and function, it is well known that they exhibit considerable compositional heterogeneity. But fundamental questions still exist as to how EV prescribed functions differ across these subpopulations. It is likely that off-target effects and inefficiencies in capturing native EV functions with engineered mimetics are due to their substantial heterogeneity. Our first hypothesis is that homogenization of EVs towards a narrow size range with uniform biomolecular content will result in a more potent and controllable drug delivery platform that maintains native EV function yet reduces off-target toxicity. Our second hypothesis is that fusion of homogenized EVs and liposomes with various functions (i.e., efficient BBB permeation through receptor mediated transcytosis) will deliver an engineered product combining desired functions. We plan on addressing these hypotheses through rigorous engineering to homogenize EVs (Aim 1) alongside biochemical assays to detangle the mechanisms important for EV intracranial delivery. We will utilize EVs isolated from gliatropic “experts”, namely a vast library of glioblastoma (GBM) patient derived primary cell lines, brain-metastasizing breast cancer cells, and other glial and neuronal cells like astrocytes and neurons. Key molecular players important for intracranial delivery identified from those studies will feedback into synthesis of engineered EVs (eEVs) via subsequent fusion with carrier EVs (Aim 2). For the engineered eEV product, we will also incorporate synthetic liposomes decorated with known ligands to trigger receptor mediated transcytosis through the BBB endothelial layer. To provide the greatest opportunity to measure efficiency of functional intracranial delivery, we plan to load formulated, labeled, and homogenized eEVs with a chemotherapeutic payload and determine drug-release profile, biodistribution, and efficacy in healthy mice with intact BBBs and then an orthotopic GBM model (Aim 3). The proposed work is important because it seeks to eliminate the highly confounding factor of particle-to-particle variability plaguing effective application of EVs as potent drug-delivery vehicles. Success in homogenizing eEVs will result in an increased underst...