Yixing Cheng

University of South Carolina, Columbia, South Carolina, United States

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Publications (3)15.87 Total impact

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    ABSTRACT: The effect of the core substituent structure on the micellar behavior of thermoresponsive amphiphilic poly(ε-caprolactone) diblock copolymer micelles was investigated through a combination of experimental and computational methods. The polycaprolactone (PCL) amphiphilic block copolymers used in this study consisted of a hydrophilic poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} block, which also endowed the polymer with thermoresponsiveness, and various hydrophobic poly(γ-alkoxy-ε-caprolactone) blocks. Five different substituents have been attached to the γ-position of the ε-caprolactone of the hydrophobic block, namely octyloxy, ethylhexyloxy, ethoxy, benzyloxy, and cyclohexylmethoxy, which self-assembled in aqueous media to generate the core of the micelles. All five synthesized diblock copolymers formed micelles in water and displayed thermoresponsive behavior with lower critical solution temperature (LCST) in the range of 36–39 °C. The impact of different substituents on the micelle properties such as size, stability, and phase transition behavior was investigated. Drug loading and release properties were also studied by employing doxorubicin (DOX) as payload. Molecular dynamics modeling was used to predict the variation of particle size, free volume, and drug loading capacity. The drug loading capacity predicted from molecular dynamics simulation was found to be comparable with the experimental data, which suggests that molecular dynamic simulations may be a useful tool to provide valuable selection criteria for the engineering of polymeric micelles with tunable size and drug loading capacity.
    Macromolecules 06/2013; 46(12):4829–4838. · 5.93 Impact Factor
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    ABSTRACT: Chemical addressability of viral particles has played a pivotal role in adapting these biogenic macromolecules for various applications ranging from medicine to inorganic catalysis. Cowpea mosaic virus possesses multiple features that are advantageous for the next generation of virus-based nanotechnology: consistent multimeric assemblies dictated by its genetic code, facile large scale production, and lack of observable toxicity in humans. Herein, the chemistry of the viral particles is extended with the use of Cu-free strain-promoted azide–alkyne cycloaddition reaction, or SPAAC reaction. The elimination of Cu, its cocatalyst and reducing agent, simplifies the reaction scheme to a more straightforward approach, which can be directly applied to living systems. As a proof of concept, the viral particles modified with the azadibenzylcyclooctyne functional groups are utilized to trigger and amplify a weak fluorescent signal (azidocoumarin) in live cell cultures to visualize the non-natural sugars. Future adaptations of this platform may be developed to enhance biosensing applications.
    Molecular Pharmaceutics 10/2012; 10(1):43–50. · 4.57 Impact Factor
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    ABSTRACT: A thermo-responsive poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone}-b-poly(γ-octyloxy-ε-caprolactone) (PMEEECL-b-POCTCL) diblock copolymer was synthesized by ring-opening polymerization using tin octanoate (Sn(Oct)(2)) catalyst and a fluorescent dansyl initiator. The PMEEECL-b-POCTCL had a lower critical solution temperature (LCST) of 38 °C, and it was employed to prepare thermally responsive micelles. Nile Red and Doxorubicin (DOX) were loaded into the micelles, and the micellar stability and drug carrying ability were investigated. The size and the morphology of the cargo-loaded micelles were determined by DLS, AFM, and TEM. The Nile-Red-loaded polymeric micelles were found to be stable in the presence of both fetal bovine serum and bovine serum albumin over a 72 h period and displayed thermo-responsive in vitro drug release. The blank micelles showed a low cytotoxicity. As comparison, the micelles loaded with DOX showed a much higher in vitro cytotoxicity against MCF-7 human breast cancer cell line when the incubation temperature was elevated above the LCST. Confocal laser scanning microscopy was used to study the cellular uptake and showed that the DOX-loaded micelles were internalized into the cells via an endocytosis pathway.
    Biomacromolecules 06/2012; 13(7):2163-73. · 5.37 Impact Factor