Local targeting in inflammatory bowel disease: Investigating the suitability of drug-loaded exosomes for oral delivery

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Inflammatory bowel disease (IBD) can result in debilitating physical and psychosocial symptoms for patients and affect society through loss of schooling, absenteeism, and health-care costs. More than 6.8 million people are estimated to be living with IBD worldwide. IBD comprises of ulcerative colitis (UC) and Crohn's disease (CD), two chronic, relapsing disorders of the gastrointestinal tract. In UC, inflammation is continuous and widespread and disturbs the superficial mucosal layer of the large intestine or the colon. CD on the other hand is characterized by deeper and more erratic inflammation that can occur throughout the entire digestive tract. First-line treatment strategies involve the use of small molecule therapeutics, including 5-aminosalicylates, corticosteroids, systemic immunomodulators and JAK inhibitors. However, due to the limited efficacy of these modalities, extensive effort has been put into developing novel biologics for the treatment of IBD, such anti-TNF-alpha and anti-integrin antibodies. The drawback of these systemic treatment strategies are the serious and sometimes fatal, adverse effects. These factors, coupled with complex dosing regimens, contribute to poor patient adherence that is in turn associated with poor clinical outcomes, increased healthcare costs, and increased rates of hospitalization and relapse. Various nano-based drug formulations have been used to improve the therapeutic efficacy and safety of chemical and biomolecular drugs. However, clinical translation of these systems is limited by their rapid clearance from the body, and the cytotoxicity of the materials used. Consequently, an endogenous nanoparticle that has been receiving increasing attention is exosomes; these are nanometre-sized lipid-bilayer-enclosed extracellular vesicles, which are released by cells to shuttle lipids, proteins and nucleic acids to neighbouring cells. Exosomes have distinct advantages over synthetic nanoparticles, such as their small size for penetration into deep tissues, limited immunogenicity, slightly negative zeta potential for long circulation, high delivery efficiency and natural targeting abilities. So far, genetic, anticancer and anti-inflammatory drugs have been successfully delivered by exosomes. In these cases, exosomes enhance the transfection efficiency of cytotoxic drugs and reduces their side effects, as well as protecting these fragile molecules from drug clearance. They are also characterised by a negative zeta-potential charge which enables them to interact with the positively charged inflamed inflammatory bowel disease tissue, making them ideal carriers for targeted oral drug delivery.This innovative project aims to formulate drug-loaded exosomes for targeted oral drug delivery to inflamed bowel tissue. We will isolate exosomes by size exclusion chromatography and differential centrifugation methods. The exosomes will then be characterised by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM) and western blotting. In-vitro and in-vivo transfection studies will be completed and an assessment of the effect of gastrointestinal mucus on the exosomes will be performed. The exosomes will be loaded with a drug cargo by electroporation and the characterisation assays repeated. They will finally be tested in-vivo for therapeutic efficacy.