Zhiyun Chen

Shape effects of nanoparticles conjugated with cell-penetrating peptides (HIV Tat PTD) on CHO cell uptake

In order to probe the nanoparticle shape/size effect on cellular uptake, a spherical and two cylindrical nanoparticles, whose lengths were distinctively varied, were constructed by the selective cross-linking of amphiphilic block copolymer micelles. Herein, we demonstrate that, when the nanoparticles were functionalized with the protein transduction domain of human immunodeficiency virus type 1 Tat protein (HIV Tat PTD), the smaller, spherical nanoparticles had a higher rate of cell entry into Chinese hamster ovary (CHO) cells than did the larger, cylindrical nanoparticles. It was also found that nanoparticles were released after internalization and that the rate of cell exit was dependent on both the nanoparticle shape and the amount of surface-bound PTD.

Helix self-assembly through the coiling of cylindrical micelles

Both single and double helical superstructures have been created through solution self-assembly of cylindrical micelles for the first time. Helical micelles were formed from the co-assembly of poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA-b-PMA-b-PS) triblock copolymers with different multiamines. The helix pitch could be adjusted by adjusting the amount and type of multiamine added. The helical structure exhibits unprecedented regularity for a nanostructure self-assembled from solution indicating the presence of strong, synergistic forces underlying the helix formation.

Nanoparticles with tunable internal structure from triblock copolymers of PAA-b-PMA-b-PS.

Polymer nanoparticles containing their own inherent nanostructure (lamellar, bicontinuous-like, or porous) were formed via the self-assembly of a triblock copolymer complexed with a multiamine counterion in mixed solvents. The internal nanostructure is due to local phase separation of the block copolymers and can be tuned by varying the solvent composition, the relative block composition, and the valency of the organic counterion.

Origins of toroidal micelle formation through charged triblock copolymer self-assembly

The toroidal micelle morphology has been produced by the self-assembly of poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA-b-PMA-b-PS) triblock copolymervia interaction with organic diamines in mixed THF/water solution. Formation of toroidal, or ring-like, micelles was controlled by the ratio of THF to water, the chain length of the polystyrene block, the type and amount of diamino counterion as well as the solution preparation procedure. Two distinct mechanisms for toroidal micelle formation are proposed. Under the appropriate solution condition, toroids can be constructed either through elimination of high-energy spherical micelles and/or cylindrical micelle endcaps, or through perforation of disc-like micelles. Slow chain dynamics of triblock copolymers in solution associated with their high molecular weight plays an important role in toroidal micelle construction. Toroidal nanostructures were characterized with both transmission electron microscopy (TEM) and cryogenic transmission electron microscopy (cryo-TEM).