Anhe Wang

Triggered release of insulin from glucose-sensitive enzyme multilayer shells.

A glucose-sensitive multilayer shell, which was fabricated by the layer-by-layer (LbL) assembly method, can be used as a carrier for the encapsulation and controlled release of insulin. In the present report, glucose oxidase (GOD) and catalase (CAT) were assembled on insulin particles alternately via glutaraldehyde (GA) cross-linking. The resulting core-shell system has been proven to be glucose-sensitive. When the external glucose was introduced, the release ratio of insulin from the protein multilayer can be increased observably. This is likely attributed to the catalysis interaction of CAT/GOD shells to glucose, which leads to the production of H(+) and thus drops the pH of the microenvironment. Under the acidic conditions, on the one hand, a part of C=N bond formed from Schiff base reaction can be broken and thus increasing the permeability of the capsule wall. On the other hand, the solubility of insulin can also be increased. The above factors may be the key control to increase the release of insulin from the multilayer. Therefore, such CAT/GOD multilayer may have a great potential as a glucose-sensitive release carrier for insulin, and may open the way for the further application of LbL capsules in the drug delivery and controlled release, etc.

Lipid coated mesoporous silica nanoparticles as photosensitive drug carriers

This paper presents a strategy for the biofunctionalization of novel photosensitizer carriers, mesoporous silica nanoparticles (MSNs). After being calcined and absorbed with photosensitizers (hypocrellin B, HB), MSNs can be coated with a lipid layer. Transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) results proved that HB molecules can be loaded into MSN porous and lipid can coated on the surface of the nanoparticles. When co-cultured with cancer cells (MCF-7), MSNs can transport HB molecules into cells and present low cytotoxicity. With the introduction of a lipid layer, the efficiency of MSN uptake by cells can be improved. These intracellular HB-loaded MSN materials also present cytotoxicity to MCF-7 cells after light irradiation which indicates the materials can be used as good photosensitizer carriers in photodynamic therapy.

Mechanical properties of tungsten fiber reinforced ZrAlNiCuSi metallic glass matrix composite

Tungsten fiber reinforced (Zr55Al10Ni5Cu30)(98.5)Si-1.5 metallic glass composites were fabricated and characterized. The mechanical properties of the composite under compression and tension were investigated. Tungsten reinforcement greatly increased compressive strain to failure compared to the unreinforced (Zr55Al10Ni5Cu30)(98.5)Si-1.5 metallic glass. The compressive failure mode changed from a single shear band to multiple shear bands and to localized fiber buckling and tilting as the volume fraction of tungsten fiber increased. The maximum tensile strength and strain to failure of each of the composites were lower than those of unreinforced material due to the lack of substantial shear bands. Tensile toughness changed to some extent due to different interface reactions. The reason for the improved mechanical properties is discussed

TiZr-base Bulk Metallic Glass with over 50 mm in Diameter

Low-cost TiZr-base bulk metallic glasses (BMGs) (Ti(36.1)Zr(33.2)Ni(5.8)Be(24.9))(100-x)Cu(x) (x=5, 7 and 9) with a maximum size of over 50 mm in diameter were developed by optimizing the alloy composition. The idea is initiated by selecting a particular microstructure comprising primary beta-Ti dendrite and amorphous phase. Afterwards, based on this composition of amorphous phase, a class of TiZr-base bulk metallic glasses was designed step by step to reach the optimum composition range. The glass transition temperature (T(g)), initial crystallization temperature (T(x)) and width of supercooled region (Delta T) of (Ti(36.1)Zr(33.2)Ni(5.8)Be(24.9))(91)Cu(9) BMG are 611, 655 and 44 K, respectively. The (Ti(36.1)Zr(33.2)Ni(5.8)Be(24.9))(91)Cu(9) BMG exhibits low density of 5.541 g.cm(-3) and high compressive fracture strength of 1800 MPa, which promises the potential application as structural materials.

Enhanced plasticity in Mg-based bulk metallic glass composite reinforced with ductile Nb particles

The authors report the synthesis of Mg-based metallic glass composite reinforced with Nb particles which are simply added during melting process. The ductile Nb particles effectively impede shear band propagation and upon yielding, deformed Nb particles distribute the load uniformly to the surrounding glassy matrix to promote the initiation and branching of abundant secondary shear bands. In contrast to the previous Mg-based metallic glass composites which fracture with very little plasticity, the composite shows great resistance to crack growth. The high strength of 900 MPa and large plasticity of 12.1 +/- 2% have made it comparable to excellent Zr- or Ti-based metallic glass composite. (c) 2006 American Institute of Physics.

Highly Loaded Hemoglobin Spheres as Promising Artificial Oxygen Carriers

Seeking safe and effective artificial blood substitutes based on hemoglobin (Hb) as oxygen carriers is an important topic. A significant challenge is to enhance the loading content of Hb in a well-defined structure. Here we report a facile and controllable avenue to fabricate Hb spheres with a high loading content by templating decomposable porous CaCO(3) particles in collaboration with covalent layer-by-layer assembly technique. The surface of the Hb spheres was further chemically modified by biocompatible polyethylene glycol to protect and stabilize the system. Multiple characterization techniques were employed to reveal the loading and density of Hb in an individual CaCO(3) particle. The results demonstrate that the strategy developed in this work is effective and flexible for construction of the highly loaded Hb spheres. More importantly, such Hb spheres retain their carrying-releasing oxygen function. It may thus have great potential to develop Hb spheres with highly loaded content as realistic artificial blood substitutes in the future.

Trace Solvent as a Predominant Factor To Tune Dipeptide Self-Assembly

Solvent molecules such as water are of key importance for tuning self-assembly in biological systems. However, it remains a great challenge to detect the role of different types of noncovalent interactions between trace solvents and biomolecules such as peptides. In this work, we discover a dominant role of trace amounts of solvents for mediation of dipeptide self-assembly, in which solvent-bridged hydrogen bonding is demonstrated as a crucial force in directing fiber formation. Hydrogen-bond-forming solvents (including ethanol, N,N-dimethylformamide, and acetone) can affect the hydrogen bonding of C═O and N-H in diphenylalanine (FF) molecules with themselves, but this does not induce π-π stacking between FF molecules. The directional hydrogen bonding promotes a long-range-ordered arrangement of FF molecules, preferentially along one dimension to form nanofibers or nanobelts. Furthermore, we demonstrate that water with strong hydrogen-bond-forming capability can notably speed up structure formation with long-range order, revealing the importance of water as a trace solvent for regulation of persistent and robust fiber formation.

A peony-flower-like hierarchical mesocrystal formed by diphenylalanine

A facile method is reported to manipulate a diphenylalanine peptide into hierarchically ordered structures with interesting peony-like flower morphology in the organic solvent tetrahydrofuran. The flowers formed in THF and showed, by scanning electron microscopy, that they are actually flake-built spherical aggregations, while the aggregations of FF that formed in other chosen organic solvents, such as DMSO and pyridine, show dispersive flakes. The building of the flower-like architectures is correlated to a nonclassical crystallization pathway. The similarity between the as-obtained peptide mesocrystals formed in different solvents has been investigated and discussed. Due to the roughness of the hierarchical peptide assemblies, an antiwetting surface is readily constructed with a low surface free energy fluoroalkylsilane.

Assembly of environmental sensitive microcapsules of PNIPAAm and alginate acid and their application in drug release

The objective of this research was to fabricate stable and environmentally sensitive (PNIPAAm/ALG)(n) microcapsules via layer-by-layer (LbL) technique. The structure, thermosensitive and pH-sensitive properties of the microcapsules were characterized by transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM), individually. MnCO(3) microparticles and melamine formaldehyde (MF) microparticles were used as templates separately. The microcapsules from MnCO(3) cores were stable over a large pH range with thermosensitive and pH-sensitive properties, while those from MF particles were unstable in basic solutions. To the end, ALG and PNIPAAm were adsorbed on recrystallized taxol alternatively, which obviously prolonged the release time of taxol above lower crystal solution temperature (LCST) of PNIPAAm.

Hierarchical gold/copolymer nanostructures as hydrophobic nanotanks for drug encapsulation

Various nanoparticles are used to fabricate innovative systems for drug encapsulation and cancer therapy. In this paper, the hierarchical core-shell nanostructures composed of gold nanoparticles and poly(dimethylsiloxane)-poly(ethylene glycol) (PDMS-PEG) block copolymers are fabricated via a hydrosilylation reaction. The obtained gold/copolymer nanocomposites display a desired amphiphilic property and can be well-dispersed in water when the PEG blocks are long enough. The hydrophobic drug hypocrellin B (HB) can be encapsulated into these water-dispersible nanocomposites based on the hydrophobic-hydrophobic interaction between HB molecules and PDMS segments. The gold/copolymer nanocomposites loaded with HB show a rational anticancer ability in the photodynamic therapy although the gold/copolymer nanocomposites without drug also have a little cytotoxicity. Such hierarchically structured core-shell nanocomposites can be considered as water-dispersible nanotanks for hydrophobic drugs in the development of multifunctional biodelivery systems.