Nanoreactors with Intracellular Catalytic Activity

Artificial organelles are typically bottom-up assembled nanoreactors that equip host cells with non-native or lost cellular functionalities.

We identified polymer-lipid hybrid vesicles based on poly(cholesteryl methacrylate) (PCMA)-block-poly(2-(dimethylamino) ethyl methacrylate) (P1) and (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) phospholipids as suitable nanocarrieres with lysosomal escape ability. Following on, we loaded these vesicles with either glucose oxidase or β-galactosidase to obtain nanoreactors. We were able to illustrate intracellular activity of these nanoreactors in RAW 267.4 macrophages using glucose and β-Gal-NONOate to produce hydrogen peroxide and nitric oxide, respectively, even in primary human macrophages in the latter case.

Enzymes tend to lose their catalytic activity within a few days, substantially limiting the long-term use of artificial organelles. We employed a salen-manganese complex (EUK)-based enzyme mimic to address this challenge. We demonstrated that Hep G2 cells equipped with EUK-loaded P1 micellar nanoreactors had improved viability when exposed to the reactive oxygen inducer paraquat compare to the controls.

Despite the promising results of the P1-based artificial organelles, biomedical applications are limited due to the inherent toxicity of P1. Therefore, we synthesized polyanions (e.g., poly(2-carboxyethyl acrylate) (P2)) and demonstrated their pH-transition in a relevant range of pH 4-5. Finally, we synthesized the block copolymer PCMA-block-P2 and showed that micelles based on these block copolymer exhibited reduced cytotoxicity and lysosomal escape ability.

Taken together, artificial organelles are an emerging concept that, with due developments, might become an interesting alternative in biomedicine.