Stem cell therapies
controlled to determine when the transport vehicle will hydrolyse to release its contents. Furthermore, exosomes are small nanoparticles, approximately 30-100 nanometres in diameter. This ensures that exosomes can reach all cells in the body as they can readily circulate through capillaries where other larger molecules might fit through. However, unlike liposomes, stem cell-grown exosomes will share identical antigenic material with the host. Consequently, levels of immunogenicity are negligible, and the drugs will not be cleared via immune responses, reducing the potential for drug delivery error (Di, 2018). Likewise, as exosomes are present ubiquitously in bodily fluid, they are extremely stable in blood plasma. Therefore, unlike liposomes, exosomes will not inflict toxic effects on body. Naturally synthesized by the body, exosomes are derived from stem cells, and can be mass produced through proliferation and differentiation in a controlled environment. Using stem cells implies that exosomes can be uniquely designed for specific therapies. One application of stem cell exosomes is screening in pathology. One distinct feature of exosomes is its unique cargo (Wilson, 2020). As the lipid bilayer preserves the interior of the exosome, the contents will remain stable. So the contents of an exosome are solely dependent on its cellular origin, making the load a molecular signature. Typically, the profile of cargo of a healthy patient is distinguishable compared to that of a sick patient. Analysis can screen for illnesses in patients and detect the part of the anatomy that is causing the disease. As a result, exosomal assessments can be used for diagnostic testing for conditions such as cancer and diabetes, leading to earlier intervention that will reduce damage caused by the untreated disease. This can be achieved through introducing empty exosomes to the bloodstream and retrieving these through a biofluid, such as urine or saliva, before analysing the contents. Another implication of stem cell exosomal research is targeted drug delivery, an alternative to using liposomes as drug transport vehicles. Exosomes have superior biochemical characteristics to liposomes due to low immunogenicity and high stability. Moreover, exosomes can be developed for targeted drug therapies as, unlike liposomes, they have surface receptors (Yeo, 2013). These are proteins found on the phospholipid bilayer of the nanoparticle with a specific structure that binds to a complementary molecule. Altering these receptors will ensure that the exosome will arrive at a desired site before secreting their cargos, a property that is absent in liposome-related therapies. This honing ability can improve the effectiveness of the drug as therapeutic agents can be loaded into the vehicle, either in vivo or in vitro, with the guarantee of reaching its destination. A related example of this is the CAR exosomes (Whitty, 2019). These are exosomes containing chimeric antigen receptor T-cells: white blood cells adapted to cause an immune response against cancerous cells. Injecting CAR exosomes intravenously would transport and safely deliver CAR T-cells, whose mechanism for destroying cancer would be triggered. A study has shown CAR exosomes present as strong indicators of an antitumoral response as they express tumour growth inhibition and increased cytotoxic T-cell activity (Benmebarek, 2019). The purpose of cytotoxic T-cells is to release proteins, perforin, that hydrolyses cell membranes, leaving the cells to die by swelling and lysis, and hence the cancerous cells (Janeway, 2001).
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