Assessment of stability, toxicity and immunogenicity of new polymeric nanoreactors for use in enzyme replacement therapy of MNGIE

The lack of a crucial metabolic enzyme can lead to accumulating substrate concentrations in the bloodstream and severe human enzyme deficiency diseases. Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE) is such a fatal genetic disorder, caused by a thymidine phosphorylase deficiency. Enzyme replacement therapy is a strategy where the deficient enzyme is administered intravenously in order to decrease the toxic substrate concentrations. Such a therapy is however not very efficient due to the fast elimination of the native enzyme from the circulation. In this study we evaluate the potential of using polymeric enzyme-loaded nanoparticles to improve the delivery of therapeutic enzymes. We constructed new 200-nanometer PMOXA-PDMS-PMOXA polymeric nanoparticles that encapsulate the enzyme thymidine phosphorylase. These particles are permeabilised for substrates and products by the reconstitution of the nucleoside-specific porin Tsx in their polymeric wall. We show that the obtained ‘nanoreactors’ are enzymatically active and stable in blood serum at 37 °C. Moreover, they do not provoke cytotoxicity when incubated with hepatocytes for 4 days, nor do they induce a macrophage-mediated inflammatory response ex vivo and in vivo. All data highlight the potential of such nanoreactors for their application in enzyme replacement therapy of MNGIE.

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