Bioreducible micelles self-assembled from amphiphilic hyperbranched multiarm copolymer for glutathione-mediated intracellular drug delivery

A new type of biodegradable micelles for glutathione-mediated intracellular drug delivery was developed on the basis of an amphiphilic hyperbranched multiarm copolymer (H40-star-PLA-SS-PEP) with disulfide linkages between the hydrophobic polyester core and hydrophilic polyphosphate arms. The resulting copolymers were characterized by nuclear magnetic resonance (NMR), Fourier transformed infrared (FTIR), gel permeation chromatography (GPC), and differential scanning calorimeter (DSC) techniques. Benefiting from amphiphilic structure, H40-star-PLA-SS-PEP was able to self-assemble into micelles in aqueous solution with an average diameter of 70 nm. Moreover, the hydrophilic polyphosphate shell of these micelles could be detached under reduction-stimulus by in vitro evaluation, which resulted in a rapid drug release due to the destruction of micelle structure. The glutathione-mediated intracellular drug delivery was investigated against a Hela human cervical carcinoma cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) measurements demonstrated that H40-star-PLA-SS-PEP micelles exhibited a faster drug release in glutathione monoester (GSH-OEt) pretreated Hela cells than that in the nonpretreated cells. Cytotoxicity assay of the doxorubicin-loaded (DOX-loaded) micelles indicated the higher cellular proliferation inhibition against 10 mM of GSH-OEt pretreated Hela cells than that of the nonpretreated ones. As expected, the DOX-loaded micelles showed lower inhibition against 0.1 mM of buthionine sulfoximine (BSO) pretreated Hela cells. These reduction-responsive and biodegradable micelles show a potential to improve the antitumor efficacy of hydrophobic chemotherapeutic drugs.

Poly(β-cyclodextrin)/curcumin self-assembly: a novel approach to improve curcumin delivery and its therapeutic efficacy in prostate cancer cells

A novel PCD/CUR self-assembly approach for improved curcumin delivery to prostate cancer cells is described. The formation of PCD/CUR was confirmed using FTIR, DSC, TGA, and SEM/TEM, and their stability and solubility under physiological conditions was demonstrated. A mechanism for self-assembly is proposed. Intracellular uptake of the self-assemblies was studied by flow cytometry and immunofluorescence microscopy. The therapeutic efficacy was determined by cell proliferation and colony formation assays using C4-2, DU145 and PC3 prostate cancer cells. The results suggest that the PCD/CUR formulation could be a useful system for improving curcumin delivery and its therapeutic efficacy in prostate cancer.

Polymerization-like multilevel hierarchical self-assembly of polymer vesicles into macroscopic superstructures with controlled complexity

We demonstrate a high-leveled hierarchical self-assembly process into fractal structures. Two hyperbranched multiarm copolymers are first coassembled into binary isotropic vesicles in the primary self-assembly. Then, these primary vesicles are in situ endowed with anisotropic hydrophobic "binding sites" through a pH-induced lateral microphase separation, undergoing an isotropic-anisotropic transition. Subsequently, the anisotropic vesicles further assemble together through the specific self-recognition between the binding sites into linear, branched, cyclization, and network-like vesicle chains. Furthermore, the obtained vesicle chains can transform into linear, branched, ring-like, and network tubes through successive vesicle fusion. Such a hierarchical process is pH-triggered and well-controlled by adjusting the vesicle compositions and is coined as "polymerization-like" self-assembly due to the striking analogy between the vesicle association model and polymerization process.

Self-assembled micelles from an amphiphilic hyperbranched copolymer with polyphosphate arms for drug delivery

A novel type of amphiphilic hyperbranched multiarm copolymer [H40-star-(PLA-b-PEP-OH)] was synthesized through a two-step ring-opening polymerization (ROP) procedure and applied to drug delivery. First, Boltorn H40 was used as macroinitiator for the ROP of L-lactide to form the intermediate (H40-star-PLA-OH). Then, the ROP of ethyl ethylene phosphate was further initiated to produce H40-star-(PLA-b-PEP-OH). The resulting hyperbranched multiarm copolymers were characterized by (1)H, (13)C, and (31)P NMR, GPC, and FTIR spectra. Benefiting from the amphiphilic structure, H40-star-(PLA-b-PEP-OH) was able to self-assemble into micelles in water with an average diameter of 130 nm. In vitro evaluation of these micelles demonstrated their excellent biocompatibility and efficient cellular uptake by methyl tetrazolium assay, flow cytometry, and confocal laser scanning microscopy measurements. Doxorubicin-loaded micelles were investigated for the proliferation inhibition of a Hela human cervical carcinoma cell line, and the Doxorubicin dose required for 50% cellular growth inhibition was found to be 1 microg/mL. These results indicate that H40-star-(PLA-b-PEP-OH) micelles can be used as safe, promising drug-delivery systems.

Amphiphilic dual brush block copolymers as "giant surfactants" and their aqueous self-assembly

Amphiphilic dual brush diblock as well as symmetrical triblock polymers were synthesized by the overlay of the reversible addition-fragmentation chain transfer (RAFT) and the nitroxide mediated polymerization (NMP) techniques. While poly(ethylene glycol) brushes served as hydrophilic block, the hydrophobic block was made of polystyrene brushes. The resulting "giant surfactants" correspond structurally to the established amphiphilic diblock and triblock copolymer known as macrosurfactants. The aggregation behavior of the novel "giant surfactants" in aqueous solution was studied by dynamic light scattering, small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) over a large range in reciprocal space. Further, the self-assembled aggregates were investigated by scanning force microscopy (SFM) after deposition on differently functionalized ultraflat solid substrates. Despite the high fraction of hydrophobic segments, the polymers form stable mesoscopic, spherical aggregates with hydrodynamic diameters in the range of 150-350 nm. Though prepared from well-defined individual polymers, the aggregates show several similarities to hard core latexes. They are stable enough to be deposited without much changes onto surfaces, where they cluster and show spontaneous sorting according to their size within the clusters, with the larger aggregates being in the center.

Synthesis of Maleimide-End Functionalized Star Polymers and Multimeric Protein-Polymer Conjugates

Protein-polymer conjugates exhibit superior properties to unmodified proteins, generating a high demand for these materials in the fields of medicine, biotechnology, and nanotechnology. Multimeric conjugates are predicted to surpass the activity of monomeric conjugates. Herein, we report a straightforward method to synthesize multimeric polymer-conjugates. Four armed poly(N-isopropylacrylamide) (pNIPAAm) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a tetra-functionalized trithiocarbonate chain transfer agent (CTA). The polymer molecular weight, architecture and polydispersity index (PDI) were verified by gel permeation chromatography (GPC), dynamic light scattering gel permeation chromatography (DLS-GPC), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. This approach afforded well-defined polymers (PDI's < 1.06) and the ability to target various molecular weights. Maleimide functional groups were introduced at the chain ends by heating the polymers in the presence of a furan-protected azo-initiator. This allowed for site-specific conjugation of V131C T4 lysozyme to the polymers to generate multimeric protein-polymer conjugates. MALDI-TOF mass spectrometry, electrospray ionization gas-phase electrophoretic-mobility macromolecule analysis (ESI-GEMMA), gel electrophoresis, and liquid chromatography tandem mass spectrometry (LC-MS/MS) of the trypsin digests demonstrated that multimeric protein-polymer conjugates had formed. This simple strategy provides ready access to star protein-polymer conjugates for application in the fields of drug discovery, drug delivery, and nanotechnology.