Polycationic β-cyclodextrin "click clusters": Monodisperse and versatile scaffolds for nucleic acid delivery

Herein, a novel series of multivalent polycationic β-cyclodextrin "click clusters" with discrete molecular weight have been synthesized, characterized, and examined as therapeutic pDNA carriers. The materials were creatively designed based on a β-cyclodextrin core to impart a biocompatible multivalent architecture and oligoethyleneamine arms to facilitate pDNA binding, encapsulation, and cellular uptake. An acetylated-per-azido- β-cyclodextrin (4) was reacted with series of alkyne dendrons (7a-e) (containing one to five ethyleneamine units) using copper-catalyzed 1,3-dipolar cycloaddition, to form a series of click clusters (9a-e) bearing 1,2,3-triazole linkers. Gel electrophoresis experiments, dynamic light scattering, and transmission electron microscopy revealed that the macromolecules bind and compact pDNA into spherical nanoparticles in the size range of 80-130 nm. The polycations protect pDNA against nuclease degradation, where structures 9c, 9d, and 9e did not allow pDNA degradation in the presence of serum for up to 48 h. The cellular uptake profiles were evaluated in Opti-MEM and demonstrate that all the click clusters efficiently deliver Cy5-labeled pDNA into HeLa and H9c2 (2-1) cells, and compounds 9d and 9e yielded efficacy similar to that of the positive controls, Jet-PEI and Superfect. Furthermore, the luciferase gene delivery experiments revealed that the level of reporter gene expression increased with an increase in oligoethyleneamine number within the cluster arms. The cytotoxicity profiles of these materials were evaluated by protein, MTT, and LDH assays, which demonstrate that all the click clusters remain nontoxic within the expected dosage range while the positive controls, Jet PEI and Superfect, were highly cytotoxic. In particular, 9d and 9e were the most effective and promising polycationic vehicles to be further optimized for future systemic delivery experiments.