Chemical Modification of Bovine Milk Exosomes, the Biological Nanoparticles of the Future, as a Contrast Agent and Drug Delivery Vehicle

Extracellular Vesicles

Pullan, Jessica Elaine. "Chemical Modification of Bovine Milk Exosomes, the Biological Nanoparticles of the Future, as a Contrast Agent and Drug Delivery Vehicle." PhD diss., North Dakota State University, 2021.

Chemically derived nanoparticles are widely used across many applications. While they showed great promise when first discovered, the main hurdles, such as clearance and targeting, have yet to be overcome. A recently discovered class of biological nanoparticles have the potential to circumvent these disadvantages. Exosomes are biological nanoparticles (30 – 150 nm) excreted from most mammalian cells. While exosomes are typically involved in cellular signaling and traditionally removed from the body to be examined for biomarkers, this work combines chemical modifications and a biological particle for diagnostics and treatment of solid tumor cancer. Exosome involvement in cancer treatment has grown over the past ten years with the encapsulation of RNA, proteins and traditional chemotherapeutics. However, this work takes these ideas and drives them into the future by using bovine milk derived exosomes as (1) an ultrasound contrasting agent and (2) a targeted and triggered chemotherapeutic drug delivery vehicle. As an ultrasound contrast agent, raw and pasteurized bovine milk exosomes were tested and found to be capable of echogenicity without altering the ability to identify key features of the exosome, including the presence of CD63 and miRNA. In the second part of this work a chemically synthesized, hypoxia responsive lipid and a tumor penetrating and targeting peptide, iRGD were integrated into the lipid bilayer of the exosome for chemotherapeutic drug delivery. These modified exosomes were characterized using a variety of techniques, including a novel adhesion assay, atomic force microscopy, and high-resolution transmission electron microscopy. The functional capacity of the modified exosomes to deliver doxorubicin to Triple Negative Breast Cancer (TNBC) cells was also evaluated using a combination of cellular internalization and cytotoxicity assays in both monolayer and 3D spheroid cultures. Overall exosomes have the iv ability to be chemically modified in a variety of ways, opening a door to a new approach to nanoparticle drug delivery and targeted imaging.

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