Huai Yang

Characterization of ultrafine γ-Fe(C), α-Fe(C) and Fe3C particles synthesized by arc-discharge in methane

Ultrafine γ-Fe(C), α-Fe(C) and Fe3C particles were prepared by arc-discharge synthesis in a methane atmosphere. The phases, morphology, structure and surface layer of the particles were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) techniques and X-ray photoelectron spectroscopy (XPS). It was found that the mean particle size ranged from 9.8 to 12.8 nm. The surface of particles mostly consisted of a carbon layer and a little oxide. Phase transformation from γ-Fe(C) to α-Fe(C) was studied by annealing in vacuum and by differential thermal analysis and thermogravimetry (DTA–TGA) measurement. The abundance of γ-Fe(C) was determined by a magnetization measurement to be approximately 30%. Phase transformation occurred between 300 and 500 °C in a flowing argon atmosphere. The Fe3C particles oxidized to α-Fe2O3 and carbon dioxide at 610 °C or so.

Electrically controllable selective reflection of chiral nematic liquid crystal/chiral ionic liquid composites.

A chiral nematic liquid crystal/chiral ionic liquid composite with unique electro-optical characteristics is reported. The composite can be switched electrically between three different light states: transparent, scattering, and mirror reflecting (see images). Moreover, the reflection bandwidth can be controlled accurately and reversibly by adjusting the intensity of the electric field applied.

Polymer stabilized liquid crystal films reflecting both right-and left-circularly polarized light

A single-layer polymer stabilized liquid crystal (PSLC) film reflecting both right- and left-circularly polarized light has been developed by a wash-out/refill method. The PSLC film was achieved by prefabricating the polymer network with a left-handed helical structure and then refilling a cholesteric liquid crystal with a right-handed helical structure into the network. The reflection intensity of the PSLC film is close to 100% when the pitch lengths of the two opposite helical structures are the same. It was demonstrated that the memory effect of the polymer network is an important mechanism for the resulting film properties.

Multiple stimuli-responsive polymeric micelles for controlled release

Multiple stimuli-responsive polymeric micelles that can respond to light, temperature and pH have been prepared by a novel polymer, pyrene-functionalized poly (dimethylaminoethyl methacrylate), where the pyrene-quaternized segments form a light-responsive shell and the unquaternized segments form a temperature/pH-responsive core. Under UV irradiation, the micelles could be dissociated; when the temperature increased above the lower critical solution temperature, the micelles shrunk. At pH 3, the micelles could be swelled/dissociated and at pH 10, the micelles could be collapsed to complex micelles. The controlled release of Nile Red from the micelle under stimuli was demonstrated. This novel multiple stimuli-responsive micelle shows potential as a new nanocarrier and delivery system.

Drug delivery systems for differential release in combination therapy

Introduction: Combination therapy with multiple therapeutic agents has wide applicability in medical and surgical treatment, especially in the treatment of cancer. Thus, new drug delivery systems that can differentially release two or more drugs are desired. Utilizing new techniques to engineer the established drug delivery systems and synthesizing new materials and designing carriers with new structures are feasible ways to fabricate proper multi-agent delivery systems, which are critical to meet requirements in the clinic and improve therapeutic efficacy. Areas covered: This paper aims to give an overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy. Multi-agent delivery systems from nanoscale to bulk scale, such as liposomes, micelles, polymer conjugates, nano/micorparticles and hydrogels, developed over the last 10 years, have been collected and summarized. The characteristics of different delivery systems are described and discussed, including the structure of drug carriers, drug-loading techniques, release behaviors and consequent evaluation in biological assays. Expert opinion: The chemical structure of drug delivery systems is the key to controlling the release of therapeutic agents in combination therapy, and the differential release of multiple drugs could be realized by the successful design of a proper delivery system. Besides biological evaluation in vitro and in vivo, it is important to speed up practical application of the resulting delivery systems.

Wide blue phase range and electro-optical performances of liquid crystalline composites doped with thiophene-based mesogens

Thiophene-based bent-shaped mesogens were firstly applied to extend the blue phase range. And the electro-optical performances of liquid crystalline composites doped with different concentration of these bent-shaped mesogens were also explored by incorporating in-plane electric field geometry.

Low voltage and hysteresis-free blue phase liquid crystal dispersed by ferroelectric nanoparticles

Electro-optical switching with low voltage, free hysteresis and fast response speed is achieved in a facile manner by dispersing a small amount of ferroelectric nanoparticles (NPs) into blue phase liquid crystal. The large dipole moment of NPs contributes to the hysteresis-free switching, whereas the low voltage operation results from the introduction of the ferroelectric properties inherent to the NPs.

Light-controllable reflection wavelength of blue phase liquid crystals doped with azobenzene-dimers

A new series of azobenzene-dimers were synthesized and doped into the blue phase liquid crystals to broaden the temperature range of BPs. It is found that not only can the reflection wavelength of BPI be reversibly controlled but BPI can also be transformed into the cholesteric phase owing to isomerization of azobenzene induced by light.

Hyperbranched poly(amine-ester) based hydrogels for controlled multi-drug release in combination chemotherapy

Combination chemotherapy has been a primary management for cancer. Thus a drug delivery system which can administer several drugs simultaneously and control the drug release at the cancer site is desired. Here we synthesized hyperbranched poly(amine-ester) (HPAE) macromers with different degrees of terminal CC modification to make injectable hydrogels as a multi-drug delivery system. The aqueous solutions of the macromers were fast transformed into hydrogel at body temperature with a low concentration (0.05 wt%) of ammonium persulfate (APS) but no activator for accelerating the polymerization, since the HPAE macromer with tertiary amines and APS themselves formed a redox system as initiator. Three different types of drugs, doxorubicin hydrochloride (Dox), 5-fluorouracil (5FU) and leucovorin calcium (LC), were used as model drugs in this experiment. This system allows locally releasing single and/or combinations of anticancer drugs simultaneously by a controllable way. Behaviors of drug release can be controlled by the drug-loading methods or/and the CC modification degree of macromers loaded with the drug molecules. The drug release period could be prolonged when the drug was loaded into the macromers with high content of CC. The HPAE macromers exhibited good biocompatibility which was evaluated in L929 and MCF7 cell lines using MTT cell proliferation assay. The swelling behavior and degradation of HPAE hydrogels in vitro were also examined. These results suggest that the HPAE hydrogels hold great potential for use as injectable systems for locally delivering single and/or multiple drugs in chemotherapy of cancer.

Synthesis and characterization of reactive poloxamer 407s for biomedical applications

The drawbacks of poloxamer hydrogel, such as dissolving quickly in aqueous solution, have limited its biomedical application. In order to improve the stability of hydrogel, a novel system was developed by combining the reversible thermo-sensitive property of poloxamer 407 and the thiol-ene reactivity between the acrylate and thiol groups. It was found that the sol-gel transition of the acrylate/thiol modified poloxamer 407 mixture could be achieved at body temperature even with a low concentration of 17.5 wt.%. Meanwhile, the reaction between the acrylate and thiol modified poloxamer 407s occurred spontaneously in mimic physiological conditions, thus the hydrogel with crosslinking structure was formed. As a result, the stability of the crosslinked hydrogel was enhanced remarkably, and the release time of the drug from the crosslinked hydrogel was about 4.0 times as long as that from the poloxamer 407 hydrogel. Invitro and invivo experiments revealed that the biocompatibilities of the modified poloxamer 407 hydrogel were similar to that of poloxamer 407. These results indicate that the modified poloxamer 407s have potential applications in controlled drug release, tissue engineering and cell encapsulation etc.