Supramolecular Polycations with a Linear-Star Architecture Containing Hydrophobic Poly[(R,S)-3-hydroxybutyrate]: Formation of DNA Micelleplexes Coated with Apolipoprotein E3 for Blood-Brain Barrier Penetrating Gene Delivery

A novel blood-brain barrier (BBB)-penetrating supramolecular gene delivery system was developed utilizing a host–guest block-building strategy to systematically screen and optimize various block compositions. Linear poly(ethylene glycol) (PEG) was coupled with hydrophobic poly[(R,S)-β-hydroxybutyrate] (PHB) blocks of varying lengths with an adamantyl (Ad) end, giving the PEG–PHB-Ad guest polymers, which were complexed with the cationic 4-arm star-shaped β-cyclodextrin-poly(2-dimethylaminoethyl methacrylate) (βCD-pDMAEMA) host polymer, resulting in the formation of linear-star pseudoblock PEG–PHB-Ad/βCD-pDMAEMA copolymers. These amphiphilic supramolecular copolymers were thoroughly characterized and assessed for the formation of DNA micelleplex nanoparticles as a gene delivery system. Through a rational selection process, an optimal host–guest configuration was identified, considering critical factors such as cytotoxicity, gene transfection efficiency, serum stability, cellular uptake, and hemolytic activity. The optimized host–guest copolymer was subsequently coated with the targeting protein apolipoprotein E3 (ApoE3), endowing it with BBB-penetrating capabilities, which was validated through an in vitro BBB transwell model.