Bioengineered Mesenchymal Stem Cell Exosome-Coated Polymeric Nanoparticles for the Treatment of Triple Negative Breast Cancer

Background: Metastasis is the leading cause of death in breast cancer worldwide. Although there have been many new agents approved for metastatic breast cancer, they are poorly efficacious. Mesenchymal stem cells (MSC) and their exosomes play a role in the tumor microenvironment and they may have tumor homing properties. Our goal is to bioengineer MSC exosome-coated polymeric nanoparticles (BioExoNP) to deliver a chemotherapeutic drug for targeted therapy of TNBC. Methods: To isolate the MSC exosomes, we grew MSC cells in exosome free media and used ultracentrifugation at 100,000 x g for exosome isolation. We used Dynamic Light Scattering (DLS) for size analysis, polydispersity index (PDI) and zeta potential (ZP). Western blotting was used for exosomal protein identification. PLGA polymeric nanoparticles were formulated using the microfluidic based Nanoassembler. Their size, PDI and ZP were obtained using DLS. To make the coated NP we used an extrusion method. High performance liquid chromatography was used for drug loading and encapsulation efficiency. Results: The MSC exosomes had a size of 77 nm, ZP of -14 mV, and PDI of 0.24. The NP also have similar results with a size 76 nm, and PDI of 0.2, however the ZP was -38. Our exosome sample was positive for known exosomal proteins and negative for all other extracellular vesicle markers. After extrusion, the ZP of our sample was closer to -14 mV which, tells us that our sample was coated in exosomal membrane. However, after extrusion we did obtain three populations of NPs: bare NPs, coated NPs and just exosomes. Our sample was further purified using centrifugation. Conclusion: In this study, we have demonstrated that exosome-coated polymeric nanoparticles can be successfully formulated with optimal characteristics. These hybrid nanoparticles were stable and uniform. In future applications, we will use this platform to formulate BioEXoNP and evaluate its therapeutic potential using in vitro and in vivo studies. Funding: Supported by a grant award number RP170301 from the Cancer Prevention and Research Institute of Texas (CPRIT).