Enzyme-Loaded Microcapsules as Intracellular Organelles for the Degradation of Nanoplastics by Cells

Increasing spills in the environment with plastic nanoparticles causes unwanted contamination. A proof-of-concept study is presented in which mammalian cells are loaded with enzymes capable of degrading capsules, here poly(ethylene terephthalate) (PET) hydrolase. Loading into cells via endocytosis is achieved by polymeric encapsulation, which upon integration of poly(ethylenimine) also provides suitable local working conditions for the enzymes. In this way, the enzymatic activity of the PET hydrolase is also maintained in the acidic environment of endosomes/lysosomes. It is demonstrated that PET nanoparticles endocytosed by cells can be degraded by cells upon exposure to encapsulated PET hydrolase enzymes. For this first, a colocalization analysis of endocytosed PET nanoparticles and encapsulated PET hydrolase is described, showing qualitatively that enzymes can encounter the plastics nanoparticles. Second, degradation of fluorescence-labeled plastics nanoparticles via enzymatic degradation is monitored in terms of loss of intracellular fluorescence over time. Limitations and potential future applications perspectives of this concept are discussed. A roadmap is presented on how this semiquantitative study could be extended into obtaining quantitative data and first applications.