Polyoxazolines with Cholesterol Lipid Anchor for Fast Intracellular Delivery

Due to the increasing challenges posed by the growing immunity to poly(ethylene glycol) (PEG), there is growing interest in innovative polymer-based materials as viable alternatives. In this study, the advantages of lipids and polymers are combined to allow efficient and rapid cytoplasmic drug delivery. Specifically, poly(2-methyl-2-oxazoline) is modified with a cholesteryl hemisuccinate group as a lipid anchor (CHEMSPOx). The CHEMSPOx is additionally functionalized with a coumarin group (CHEMSPOx-coumarin). Both polymers self-assembled in water into vesicles of ≈100 nm and are successfully loaded with a hydrophobic model drug. The loaded vesicles reveal high cellular internalization across variant cell lines within 1 h at 37 °C as well as 4 °C, albeit to a lesser extent. A kinetic study confirms the fast internalization within 5 min after the sample's addition. Therefore, different internalization pathways are involved, e.g., active uptake but also nonenergy dependent mechanisms. CHEMSPOx and CHEMSPOx-coumarin further demonstrate excellent cyto-, hemo-, and membrane compatibility, as well as a membrane-protecting effect, which underlines their good safety profile for potential biological intravenous application. Overall, CHEMSPOx, as a lipopolyoxazoline, holds great potential for versatile biological applications such as fast and direct intracellular delivery or cellular lysis protection.