Aming Xie

Synthesis and characterization of a novel semi-IPN hydrogel based on Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate).

Salecan is a novel water-soluble, high molecular mass extracellular β-glucan produced by Agrobacterium sp. ZX09. Salecan has excellent physicochemical and biological properties, making it very suitable for hydrogel preparation. In this study, a series of novel semi-interpenetrating polymer network (semi-IPN) hydrogels containing Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethylmethacrylate) (poly(DMAA-co-HEMA)) were synthesized by radical polymerization and semi-IPN technology. Structure and morphology of the hydrogels were characterized by FTIR, XRD, TGA and SEM. The semi-IPNs had a well-interconnected porous structure with tunable pore size ranging from 6 to 41μm. Swelling capability of the hydrogels was improved by introducing the hydrophilic Salecan. Rheological results indicated that the incorporation of poly(DMAA-co-HEMA) into hydrogels enhanced the storage modulus. Compression tests revealed that these semi-IPNs were robust materials with compressive modulus between 13.3 and 90.5kPa, the addition of Salecan increased the fracture strain from 71.1% to 88.8%. Degradation and cytotoxicity tests demonstrated that semi-IPNs were degradable and non-toxic.

Synthesis and characterization of a novel hydrogel: salecan/polyacrylamide semi-IPN hydrogel with a desirable pore structure

Salecan is a novel water-soluble β-glucan produced by a salt-tolerant strain Agrobacterium sp. ZX09 which was isolated from a soil sample in our laboratory and the 16S rDNA sequence of this novel strain was deposited in the GenBank database under the accession number GU810841. Salecan has excellent physicochemical properties and can be used in industries such as food and medicine. In this paper, novel semi-interpenetrating polymer network (semi-IPN) hydrogels based on salecan and polyacrylamide (PAAm) were synthesized by radical polymerization/cryopolymerization and semi-IPN techniques. The resulting hydrogels with different salecan/PAAm composition ratios and preparation temperatures were characterized using FTIR, XRD, TGA and SEM measurements. The semi-IPNs exhibited a homogeneous porous architecture with a tunable pore size in a very broad range of 5-150 μm. Furthermore, swelling behaviors of the hydrogels were also studied to investigate the response properties of the hydrogels. The hydrogels obtained at subzero temperature can attain the equilibrium state in water within 260 seconds. Mechanical measurements showed that all semi-IPNs possessed good mechanical properties. In vitro degradation was also studied in PBS solution. Cytotoxicity results suggested that semi-IPN hydrogels were non-toxic to COS-7 cells. A cell culture experiment performed using COS-7 cells revealed their appropriateness for cell adhesion. Together, these results make salecan/PAAm semi-IPNs promising materials for biomedical applications.

A releasable disulfide carbonate linker for polyethyleneimine (PEI)-based gene vectors

In this study, a releasable disulfide carbonate linker is used to prepare disulfide-containing crosslinked polyethyleneimines (PEI-SS-CLs) for gene delivery. ESI-MS analysis shows that after being incubated with 1,4-dithio-DL-threitol (DTT), the degradable linkages in the polyethyleneimine (PEI) derivatives undergo disulfide bond cleavage followed by intramolecular cyclization and cleavage of the neighboring carbamate bond. Moreover, it is observed that thiol/polyanions trigger the release of DNA from polyplexes via the reductive degradability of PEI-SS-CLs and ion-exchange. In vitro transfection results indicate that PEI-SS-CL-1.5 (at a crosslinker/PEI feed molar ratio of 1.5) exhibits higher transfection efficacy than the commercially available reagents such as the high molecular weight PEI with a molecular weight of 25 kDa (PEI 25k) and the versatile liposomes Lipofectamine 2000. PEI-SS-CL-1.5 also demonstrates significantly lower cytotoxicity, compared with PEI 25k and Lipofectamine 2000. Our study indicates that incorporating the thiol-specific cleavable disulfide bond into crosslinked PEIs and implementing regulated release of DNA are effective strategies for designing safe and effective gene vectors.

Construction of efficacious hepatoma-targeted nanomicelles non-covalently functionalized with galactose for drug delivery

Polymeric micelles with surface immobilized galactose (Gal) are promising candidates for hepatoma-targeted drug delivery. Herein, a novel hepatoma-targeted micellar system was prepared through the non-covalent attachment of Gal to the micellar surface. A series of pH-responsive methoxyl poly(ethylene glycol)-b-poly(β-amino ester) (MPEG-PBAE) consisting of a hydrophobic alkyl chain were easily synthesized through Michael addition between amine monomer and diarcrylate. The micelles of the pH-responsive polymers exhibited stability at physiological pH and accelerated doxorubicin (DOX) release without burst release in response to an acidic pH environment. Furthermore, N-(1-deoxylactitol-1-yl) dodecylamine (Gal-C12) as a targeting ligand was successfully bound to the micellar surface by hydrophobic interaction. The results of cellular uptake, in vitro cytotoxicity and cell cycle analysis indicated that the Gal functionalized micelles effectively transferred DOX to hepatoma cells (e.g. HepG2 cells) via asialoglycoprotein receptor (ASGPR) mediated endocytosis, released DOX from the micelles and resulted in enhanced proliferation inhibition efficacy. The ease of surface functionalization and enhanced drug efficacy make the present platform promising for hepatoma-targeted drug delivery in cancer therapy.

Ultra-broad polypyrrole (PPy) nano-ribbons seeded by racemic surfactants aggregates and their high-performance electromagnetic radiation elimination

Ribbon-like nano-structures possess high aspect ratios, and thus have great potential in the development of high-performance microwave absorption (MA) materials that can effectively eliminate adverse electromagnetic radiation. However, these nano-structures have been scarcely constructed in the field of MA, because of the lack of efficient synthetic routes. Herein, we developed an efficient method to successfully construct polypyrrole (PPy) nano-ribbons using the self-assembly aggregates of a racemic surfactant as the seeds. The frequency range with a reflection loss value of lower than -10 dB reached 7.68 GHz in the frequency range of 10.32-18.00 GHz, and surpassed all the currently reported PPy nano-structures, as well as most other MA nano-materials. Through changing the amount of surfactant, both the nano-structures and MA performance can be effectively regulated. Furthermore, the reason behind the high-performance MA of PPy nano-ribbons has been deeply explored. It opens up the opportunity for the application of conducting polymer nano-ribbons as a lightweight and tunable high-performance MA material, especially in applications of special aircraft and flexible electronics.

Cationic Charged Polymer Vesicles from Amphiphilic PEI-g-PSSA-g-PEI as Potential Gene Delivery Vehicles

Polymer vesicles have attracted extensive interest for a variety of biomedical applications. Herein, novel polymer vesicles are prepared by the self-assembly of amphiphilic polyethyleneimine-g-poly(disulfide amine)-g-polyethyleneimine (PEI-g-PSSA-g-PEI) for gene delivery. To investigate the effect of hydrophobicity on transfection efficiency, a small series of PEI-g-PSSA-g-PEI were prepared under uniform conditions containing PEI fragments of the same molecular weight. The hydrophobicity of PEI-g-PSSA-g-PEI was adjusted by varying the hydrophobic content in the poly(disulfide amine) backbone and by choosing hydrophobic monomers ranging in length from C12 to C16. The hydrophobicity of polymers was also related to DNA binding affinity. Polymer vesicles obtained from the water-insoluble polymers condensed with DNA into polyplexes with sizes below 200 nm and surface charge ranging from +10 to +35 mV that were suitable for cell endocytosis. DNA polyplexes exhibited an inverted hexagonal structure, observed by transmission electron microscopy. The results of in vitro transfection demonstrate that the hydrophobic–hydrophilic balance of copolymers greatly affects their transfection properties. The top-performing polymer, II-70 %, showed improved transfection efficiency and significantly lower cytotoxicity on COS-7 cells when compared with commercial reagents polyethyleneimine (PEI 25K) and Lipofectamine 2000. These results indicate that cationic polymer vesicles with tunable hydrophobicity are promising materials for gene delivery.

Controlled hydrothermal temperature provides tunable permittivity and an improved electromagnetic absorption performance of reduced graphene oxide

Reduced graphene oxide (RGO) has been prepared by a hydrothermal reduction method to explore the effects of reaction temperature on its permittivity and electromagnetic absorption (EA) performance. This study shows that by controlling the oxygen functional groups on the RGO surface it is also possible to obtain an ideal EA performance without any other decorated nanomaterials.

Tetrazole amphiphile inducing growth of conducting polymers hierarchical nanostructures and their electromagnetic absorption properties

Conducting polymers (CPs) at nano scales endow materials with special optical, electrical, and magnetic properties. The crucial factor to construct and regulate the micro-structures of CPs is the inducing reagent, particular in its chemical structure, such active sites, self-assembling properties. In this paper, we design and synthesize an amphiphile bearing tetrazole moiety on its skeleton, and use this amphiphile as an inducing reagent to prepare and regulate the micro-structures of a series of CPs including polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene) and poly(p-phenylenediamine). Because of the unique electric properties of CPs and size effect, we next explored the electromagnetic absorption performances of these CPs nanostructures. A synergetic combination of electric loss and magnetic loss is used to explain the absorption mechanism of these CPs nano-structures.

Superfine palladium nanocrystals on a polyphenylene framework for photocatalysis

The design of high-efficiency photocatalysts is a crucial step to convert light energy for chemical synthesis. In this study, a Pd/polyphenylene (PPh) photocatalyst was synthesized via a palladium catalyzed Suzuki coupling reaction and the in situ pyrolysis of a Pd precursor. A two-stage heating strategy was developed to successfully control the size distribution of loaded Pd nanocrystals. This Pd/PPh catalyst displayed excellent photocatalytic activity during a p-nitrophenol reduction evaluation test. The results indicated that the enhanced catalytic activity could be mainly attributed to synergetic promotion between the Pd nanocrystals and the PPh framework, as well as the high-efficiency light harvesting and energy transfer by the conjugate skeleton of PPh. This research opens up the exploration of conjugate polymers as photoactive carriers for the design of high-efficiency photocatalysts.