Supramolecular Polycations with a Linear-Star Architecture Containing Hydrophobic Poly[(<i>R</i>,<i>S</i>)-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[(<i>R</i>,<i>S</i>)-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 <i>in vitro</i> BBB transwell model.