Artificial Organelles with Lysosomal Escape Capability

Research output: Book/anthology/dissertation/reportPh.D. thesisResearch

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  • Bo Thingholm
A broad range of diseases is linked to the malfunctioning of a single enzyme. These are often relentlessly progressive with high morbidity and mortality. While success have been achieved through treatments such as enzyme replacement therapy, there are inescapable limitations connected to conventional enzyme replacement therapy. These include the degradation of the therapeutic enzymes by proteases and clearance from circulation by the mononuclear phagocyte system. To come up with a sustained solution, we assembled intracellular active subcompartmentalized nanoreactors featuring a model enzyme encapsulated into liposomal subunits. Despite the initial success, we wanted to go beyond this to address key challenges such as the lacking ability of carrier systems to facilitate escape from the endocytic pathway and the loss of enzymatic function over extended periods. Herein, hybrids vesicles composed of the diblock copolymer poly(cholesteryl methacrylate)-block-poly(2-dimethylaminoethyl methacrylate) and phospholipids were assembled. Confocal laser scanning microscopy images demonstrated the ability of the hybrids to facilitate endosomal/lysosomal escape. To address the loss of enzymatic function over time, a novel salen-maganese complex (EUK-B) was synthesized. The complex proved as an efficient mimic of the natural enzyme, catalase, in decomposing hydrogen peroxide, both free in solution and when encapsulated into micelles, composed of the diblock copolymer poly(cholesteryl methacrylate)-block-poly(2-dimethylaminoethyl methacrylate). Further, HepG2 cells exposed to low concentrations of micelle encapsulated EUK-B exhibited resistance towards paraquat induced oxidative stress. However, as revealed in both studies, the poly(2-dimethylaminoethyl methacrylate) block induces high levels of cytotoxicity, setting an inherent limit to the concentrations that can be used. To address this, two novel anionic polymers with a biological relevant pH transition were synthesized. These were shown to facilitate lysosomal escape when used as the terminal layer on a silica substrate. The colloids featuring the anionic polymers elicited significantly lower cytotoxicity compared to previously reported pH responsive polymers. While most reported examples of lysosomal escape aims at releasing the therapeutic cargo into the cytosol, the reported colloids demonstrated the potential to navigate intact artificial organelles out of the lysosomes and into the cytosol. Taken together, the findings presented here possess the potential to broaden the portfolio of vesicular nanocarriers for cytosolic drug delivery and thereby the ability to serve as intracellular active artificial organelles.
Original languageDanish
PublisherAarhus Universitet
Number of pages118
Publication statusPublished - Jun 2019

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