Cobalt-Polypyrrole/Melamine-Derived Co-N@NC Catalysts for Efficient Base-Free Formic Acid Dehydrogenation and Formylation of Quinolines through Transfer Hydrogenation.

It is highly desired but remains a great challenge to develop non-noble metal heterogeneous catalysts to supersede noble metal catalysts for formic acid (FA) dehydrogenation and the corresponding transfer hydrogenation reactions. Herein, we developed a simple and feasible melamine-assisted pyrolysis strategy for the preparation of atomic cobalt-nitrogen (Co-N)-anchored mesoporous carbon with high metal loading (>6.8 wt %) and high specific surface area (750 m2 g-1). Systematic investigation reveals that both the organic carbon source polypyrrole and the nitrogen source melamine are crucial for the successful generation of such Co-N-based materials. The obtained samples (Co-N)n@NC were demonstrated to be highly efficient and robust catalysts for FA dehydrogenation and formylation of quinolines through transfer hydrogenation, exhibiting a very high hydrogen production rate of 16 451 mL·gCo-1·h-1 for FA dehydrogenation and affording excellent yields (up to 99%), selectivity (up to 98%), and stability for transfer hydrogenation. This work may provide a promising route for the fabrication of more low-cost metal-nitrogen catalysts for green fine chemical synthesis.

Preparation and controlled drug release ability of the poly[N-isopropylacryamide-co-allyl poly(ethylene glycol)]-b-poly(γ-benzyl-l-glutamate) polymeric micelles.

The polymeric micelles were prepared through a copolymerization of allyl polyethylene glycol (APEG) and N-isopropylacrylamide in the presence of 2-aminoethanethiol (AET), followed by a ring opening polymerization of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA). Doxorubicin (DOX) as a model drug was covalently conjugated into the core of micelles via hydrazone bonds. The drug loading capacity could reach up to 15% with drug encapsulation efficiency of 80%. The pH/thermo sensitivities were observed in the process of in vitro drug release. The DOX-loaded micelles exhibited accelerated drug release behaviors in an acidic condition, and enhanced therapeutic efficacy was observed. Furthermore, the cytotoxicity of micelles against Hela and 3T3 cells was evaluated before and after drug loading. The DOX-loaded micelles showed strong cytotoxic activity to the cancer cells. But the blank micelles showed non-cytotoxicity. Therefore, the thermo/pH dual-responsive polymeric micelles have a promising future applied as a controlled drug delivery system for anticancer drugs.

Preparation of pH/redox dual responsive polymeric micelles with enhanced stability and drug controlled release.

Stimuli-responsive polymeric micelles were prepared through self-assembly of amphiphilic copolymers poly(ethylene glycol)-poly(γ-benzyl l-glutamate), followed by a core-crosslinking reaction using cystamine as the crosslinking agent. The crosslinked micelles with spherical morphologies in nanometer size showed enhanced stability against dilution and concentrated salt solutions compared to the micelles before crosslinking. Doxorubicin (DOX) as a model drug was encapsulated into the core of micelles through electrostatic interactions between carboxylic acid and DOX. In vitro drug release under pH and redox conditions was investigated. Furthermore, the cytotoxicity of micelles was evaluated before and after drug loading. The endocytosis of DOX-loaded micelles and the intracellular drug release were studied. DOX-loaded micelles exhibited accelerated drug release behaviors in an acidic and reductive environment, and showed an inhibited premature release behavior as compared to the noncrosslinked micelles. Considering their enhanced stability, pH and redox dual triggered responsive characteristics, the polymeric micelles can serve as potential systems for controlled drug delivery.

Studies on the preparation and controlled release of redox/pH-responsive zwitterionic nanoparticles based on poly-L-glutamic acid and cystamine.

The enhancement of tumor intracellular drug uptake and resistance against nonspecific protein adsorption are essential for an injectable anticancer drug carrier. In the present study, a new type of redox/pH-responsive zwitterionic nanoparticles (NPs) was prepared using poly-L-glutamic acid and cystamine in aqueous solutions under mild conditions. The NPs showed surface charge convertible feature in response to pH change of the solutions. The NPs demonstrated excellent anti nonspecific protein adsorption. In vitro release profiles of the NPs, they showed redox/pH dual sensitivities in vitro release. The effective intracellular delivery behaviors were verified through investigation of cell viability, and confocal laser scanning microscopy observation of HeLa cells after incubation with the DOX-loaded NPs. The NPs were non-cytotoxic and would have potential applications as a drug delivery vehicle for enhancing intracellular uptake of anticancer drugs.

Preparations of hyperbranched polymer nano micelles and the pH/redox controlled drug release behaviors.

Hyperbranched polymer nano micelles (NMs) were prepared through a nucleophilic ring opening polymerization between cystamine and polyethylene glycol diglycidyl ether, followed by a reaction of amino groups and dimethyl maleic anhydride. The NMs showed spheric morphologies with hydrodynamic diameters of 106-120nm. Doxorubicin was loaded in the NMs with loading rate as high as 15.38wt%; The NMs possessed negative zeta potentials in aqueous solutions of pH7.4 due to the carboxyl ions on the particle surfaces, but the zeta potentials were converted to positive ones due to the hydrolysis of amide bonds at pH5.0-6.5, leading to the leaving of carboxyl groups and remaining of amino groups. The disulfide bonds in cystamine were designed in the hyperbranched polymer structures of the NMs, and bonds could be broken by a reducing agent l-glutathione (GSH) (10mM), resulting in a targeted drug release. The smart NMs displayed good biodegradability and biocompatibility, and they could be potentially used in drug controlled release field.

Preparations and doxorubicin controlled release of amino-acid based redox/pH dual-responsive nanomicelles.

Terpolymers of poly (Lysine-co-N, N-Bis (acryloyl) cystamine-co-ß-Phenethylamine) (PLBP) were synthesized in one-pot by Michael addition terpolymerization. The terpolymers self-assembled into nano-sized spherical micelles (84-123nm) with narrow distributions. The surface charge of the nanomicelles (NMs) was depended on solution's pH and showed negative values under physiological conditions (pH7.4), which was beneficial for long circulation without non-specific protein adsorption. Doxorubicin (DOX) was effectively loaded into the NMs for controlled release. The in vitro release profiles exhibited obvious pH and reduction sensitivities in response to the environment mimicking tumor cells. The MTT assays demonstrated that blank NMs were biocompatible, and drug-laden NMs showed a significant cytotoxicity on Hela cells. The NMs could be potentially applied as smart drug delivery systems in cancer therapy.

Gas promotes the crystallization of nano-sized metal-organic frameworks in ionic liquid.

Herein it was found that gas can be utilized as an activator to promote metal-organic framework (MOF) crystallization in IL at room temperature. The ultra-small MOF nanoparticles were obtained, and their size and porosity properties can be easily modulated by controlling gas pressure. The as-synthesized nano-sized Cu-MOF is an excellent candidate catalyst for the solvent-free oxidation of cyclohexene with oxygen.

Assembly of Mesoporous Metal-Organic Framework Templated by an Ionic Liquid/Ethylene Glycol Interface.

We propose a facile room-temperature synthesis of a metal-organic framework (MOF) with a bimodal mesoporous structure (3.9 and 17-28 nm) in an ionic liquid (IL)/ethylene glycol (EG) mixture. The X-ray diffraction analysis reveals that MOF formation can be efficiently promoted by the presence of the EG/IL interface at room temperature. The MOFs with mesoporous networks are characterized by SEM and TEM. The formation mechanism of the mesoporous MOF in EG/IL mixture is investigated. It is proposed that the EG nanodroplets in the IL work as templates for the formation of the large mesopores. The as-synthesized mesoporous metal-organic framework is an effective and reusable heterogeneous catalyst to catalyze the aerobic oxidation of benzylic alcohols.