Poly(2-oxazoline)-Based Lipid Nanocapsules Containing Free Hydroxyl Group as Promising Alternative to Conventional PEG-Lipid Nanocapsules

Lipid nanocapsules (LNCs) are attractive nanocarriers owing to their high colloidal stability and cytocompatibility. However, their current formulation relies on the poly-(ethylene glycol) (PEG)-based surfactant Kolliphor HS 15, whose clinical use is increasingly compromised by the emergence of anti-PEG antibodies leading to rapid clearance of PEGylated treatments. Poly-(2-oxazoline)-s (POx) share various similarities with PEG such as stealth properties, neutrality, high water solubility, cytocompatibility with enhanced chemical tunability and lower immunogenicity. Here, we report the synthesis of two POx-based surfactants using a copper-free azide-alkyne cycloaddition, enabling their efficient conjugation with hydrophobic chains under conditions compatible with biological applications. Incorporation of these surfactants into LNCs provided nanoparticles with hydrodynamic diameters of ∼63-74 nm and concentrations around 10¹⁴ nps mL^-1, determined by dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). These POx LNCs displayed high colloidal stability over one month. In vitro cytotoxicity assays were performed on HeLa, HEK293 and B16F10 cancer cell lines, confirming the high cytocompatibility of POx LNCs, comparable to PEG LNCs of the same size. Finally, in vivo studies further demonstrated their low cytotoxicity, highlighting POx LNCs as robust PEG-free nanocarriers with strong potential for next-generation biomedical applications.