Ruibin Wang

Synthesis and Gene Delivery of Poly(amido amine)s with Different Branched Architecture

A general strategy to improve the transfection efficiency as well as lower the cytotoxicity for polycationic vectors has been developed. Through the polycondensation addition of N,N-methylene bisacrylamide and 1-(2-aminoethyl)piperazine in a water/N,N-dimethylformamide cosolvent, a series of cationic poly(amido amine)s with same repeating units but different branched architecture have been prepared. With the increase in branched architecture, the cationic polymers become more and more compact, accompanied by the enhancement of primary and tertiary amino groups. Therefore, the buffering capacities and DNA condensation capabilities of cationic poly(amido amine)s are strengthened greatly, whereas the correspondent cytotoxicity decreases. Correspondingly, the transfection efficiency is improved by more than three orders of magnitude. The results of this study indicate that the gene delivery can be readily regulated by only changing the branched architecture of polycations.

Polymeric micelles with water-insoluble drug as hydrophobic moiety for drug delivery.

The hydrophobic block of polymeric micelles formed by amphiphilic copolymers has no direct therapeutical effect, and the metabolites of these hydrophobic segments might lead to some unexpected side effects. Here the hydrophobic core of polymeric micelles is replaced by highly water-insoluble drugs themselves, forming a new micellar drug delivery system. By grafting hydrophobic drugs of paclitaxel (PTX) onto the surface of hydrophilic hyperbranched poly(ether-ester) (HPEE), we constructed an amphiphilic copolymer (HPEE-PTX). HPEE-PTX could self-assemble into micellar nanoparticles in aqueous solution with tunable drug contents from 4.1 to 10.7%. Moreover, the hydrolysis of HPEE-PTX in serum resulted in the cumulative release of PTX. In vivo evaluation indicated that the dosage toleration of PTX in mice had been improved greatly and HPEE-PTX micellar nanoparticles could be used as an efficient prodrug with satisfactory therapeutical effect. We believe that most of the lipophilic drugs could improve their characters through this strategy.

Role of Branching Architecture on the Glass Transition of Hyperbranched Polyethers

The influence of branching architecture on the glass transition of hyperbranched polyethers has been investigated. For amorphous samples, the glass transition temperature (T(g)) first increases with the degree of branching (DB), passes through a maximum, and then decreases sharply. An attempt is made to explain this by the competition between the junction density and the free volume of terminal units. For the crystalline samples, the crystallization of polymer chains makes the relationship of DB and T(g) more complicated. By the introduction of branching architecture, the crystallization ability of the branched polymer is weakened gradually. When the samples are isothermally crystallized for a long time, the T(g) of polyethers decreases monotonically with DB.

Amorphous carbon dots with high two-photon fluorescence for cellular imaging passivated by hyperbranched poly(amino amine)

Amorphous carbon dots (C-Dots) with high two-photon fluorescence were prepared by using citric acid (CA) as the carbon source and hyperbranched poly(amino amine) (HPAA) as the surface passivation agent through a facile hydrothermal approach. The C-Dots with an average diameter about 10 nm were readily dispersed in water. They exhibited excellent fluorescence properties and excitation-dependent fluorescence behavior with the corresponding quantum yield (QY) of 17.1% in aqueous solution. Interestingly, the C-Dots emitted bright fluorescence even in the solid state with a QY of 16.3%, which is the highest value obtained for carbon-based nanomaterials. Using the MTT assay, the C-Dots showed low cytotoxicity against L929 normal cells. Furthermore, they were easily internalized by HeLa cells and presented high quality one- and two-photon cellular imaging, suggesting significant potential for application in biological imaging.

Aptamer-Functionalized and Backbone Redox-Responsive Hyperbranched Polymer for Targeted Drug Delivery in Cancer Therapy

A novel type of backbone redox-responsive hyperbranched poly(2-((2-(acryloyloxy)ethyl)disulfanyl)ethyl 4-cyano-4-(((propylthio)carbonothioyl)-thio)-pentanoate-co-poly(ethylene glycol) methacrylate) (HPAEG) has been designed and prepared successfully via the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization and self-condensing vinyl polymerization (SCVP). Owing to the existence of surface vinyl groups, HPAEG could be efficiently functionalized by DNA aptamer AS1411 via Michael addition reaction to obtain an active tumor targeting drug delivery carrier (HPAEG-AS1411). The amphiphilic HPAEG-AS1411 could form nanoparticles by macromolecular self-assembly strategy. Cell Counting Kit-8 (CCK-8) assay illustrated that HPAEG-AS1411 nanoparticles had low cytotoxicity to normal cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) results demonstrated that HPAEG-AS1411 nanoparticles could be internalized into tumor cells via aptamer-mediated endocytosis. Compared with pure HPAEG nanoparticles, HPAEG-AS1411 nanoparticles displayed enhanced tumor cell uptake. When the HPAEG-AS1411 nanoparticles loaded with anticancer drug doxorubicin (DOX) were internalized into tumor cells, the disulfide bonds in the backbone of HPAEG-AS1411 were cleaved by glutathione (GSH) in the cytoplasm, so that DOX was released rapidly. Therefore, DOX-loaded HPAEG-AS1411 nanoparticles exhibited a high tumor cellular proliferation inhibition rate and low cytotoxicity to normal cells. This aptamer-functionalized and backbone redox-responsive hyperbranched polymer provides a promising platform for targeted drug delivery in cancer therapy.

Design and synthesis of cationic drug carriers based on hyperbranched poly(amine-ester)s.

Novel cationic drug carriers based on hyperbranched poly(amine-ester)s were successfully prepared through proton-transfer polymerization. Both vinyl and epoxy groups of commercially available glycidyl methacrylate monomer could be polymerized through oxyanionic initiation of triethanolamine in the presence of potassium hydride catalysis. By changing the molar ratios of triethanolamine/glycidyl methacrylate or potassium hydride/triethanolamine, we obtained a series of hyperbranched poly(amine-ester)s. The generation of highly branched poly(amine-ester)s was confirmed by (13)C DEPT-135 NMR and 2D NMR techniques, and their degrees of branching were found to be 0.47 to 0.68. The structure and properties of hyperbranched poly(amine-ester)s were analyzed by dynamic light scattering, gel permeation chromatography, Fourier transformed infrared, differential scanning calorimeter, and zeta-potential measurements. Methyl tetrazolium (MTT) assay suggested that the cell viability after 48 h incubation with hyperbranched poly(amine-ester) concentrations up to 1 mg/mL remained nearly 100% compared with the untreated cells. The high cellular uptake of these cationic polymers was confirmed by flow cytometry and confocal laser scanning microscopy. Furthermore, conjugation of a model hydrophobic anticancer drug chlorambucil to hyperbranched poly(amine-ester)s inhibited the proliferation of MCF-7 breast cancer cells. MTT assay indicated that the chlorambucil dose required for 50% cellular growth inhibition against MCF-7 cells was 120 microg/mL. All of these results show that hyperbranched poly(amine-ester)s are promising materials for drug delivery.

In situ preparation of magnetic nonviral gene vectors and magnetofection in vitro

Magnetic nonviral gene vectors were in situ prepared in the presence of ferrous salts and hyperbranched poly(ethylenimine)s (HPEI) with different molecular weights. HPEI, one of the most promising nonviral vectors, was not only utilized as the nanoreactor and stabilizer to prepare magnetic nanoparticles, but also skillfully used as a base supplier to avoid introducing alkali hydroxide or ammonia. Magnetic nonviral gene vectors with various magnetite contents and saturation magnetizations were obtained by changing the weight ratio of HPEI to FeSO(4).7H(2)O and the molecular weight of HPEI. MTT assays suggested that the resulting magnetite/HPEI gene vectors had lower cytotoxicity compared with pure HPEI. The magnetite/HPEI nonviral gene vectors were used for magnetofection. It was found that the luciferase expression level mediated by magnetite/HPEI in COS-7 cells under a magnetic gradient field was approximately 13-fold greater than that of standard HPEI transfection.

Preparation of CdS Nanocrystals within Supramolecular Self-Assembled Nanoreactors and Their Phase Transfer Behavior

A new strategy for the synthesis of CdS nanocrystals (NCs) within supramolecular self-assembly nanoreactors has been described. The self-assembly nanoreactors were readily constructed through the electrostatic interactions and ion pairs between palmitic acid and the terminal amine groups of hyperbranched polymer. In a chloroform/water two-phase system, aqueous Cd (2+) ions were spontaneously encapsulated into the cavities of self-assembly nanoreactors in chloroform. After reaction with S (2-) ions, the CdS NCs with high stability were obtained. By the addition of excess triethylamine, CdS NCs formed in the self-assembly nanoreactors were transferred from organic phase into aqueous phase. After dialysis and rotorary evaporation, aqueous CdS NCs could be redispersed into chloroform solution containing palmitic acid.

Temperature-induced emission enhancement of star conjugated copolymers with poly(2-(dimethylamino)ethyl methacrylate) coronas for detection of bacteria.

A facile strategy for temperature-induced emission enhancement of star conjugated copolymers has been developed for biodetection. The star copolymers (HCP-star-PDMAEMAs) with different poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) chain lengths were synthesized from the hyperbranched conjugated polymer (HCP) macroinitiator by atom transfer radical polymerization (ATRP). The star conjugated copolymers exhibited interesting thermoresponsive phase transitions with adjustable lower critical solution temperature (LCST) depending on the pH of copolymer solution. Above the LCST, the emission of HCP-star-PDMAEMAs was enhanced greatly through restriction of intermolecular aggregation of conjugated polymer cores by the collapse of PDMAEMA arms. By changing the PDMAEMA length, the emission performance of HCP-star-PDMAEMAs could be readily adjusted. Correspondingly, this temperature-dependent emission enhancement of HCP-star-PDMAEMAs was successfully applied in the highly sensitive detection of bacteria. Due to the existence of a hyperbranched conjugated core and many thermo-responsive PDMAEMA arms, the detection limit of E. coli could reach 10(2) cfu mL(-1).

Synthesis, Characterization, and in Vitro Evaluation of Long-Chain Hyperbranched Poly(ethylene glycol) as Drug Carrier

A series of novel long-chain hyperbranched poly(ethylene glycol)s (LHPEGs) with biodegradable connections were designed and synthesized in one pot through proton-transfer polymerization using PEG and commercial glycidyl methacrylate as monomers and potassium hydride as catalyst. The LHPEGs were hydrolyzed at neutral pH resulting in the decrease of molecular weights. In vitro evaluation demonstrated that LHPEGs were biocompatible and displayed negligible hemolytic activity. The efficient cellular uptake of LHPEGs was confirmed by flow cytometry and confocal laser scanning microscopy. Moreover, conjugation of a model hydrophobic anticancer drug methotrexate to LHPEGs inhibited the proliferation of a human cervical carcinoma Hela cell line. MTT assay indicated that the conjugated methotrexate dose required for 50% cellular growth inhibition against Hela cells was 20 μg/mL. By combining the advantages of long-chain hyperbranched structure and PEG, LHPEG provides a promising drug carrier for therapeutic fields.