Zhonghao Li

Dielectric relaxor properties of K0.5Bi0.5TiO3 ferroelectrics prepared by sol–gel method

Lead-free potassium–bismuth titanate, K0.5Bi0.5TiO3 (KBT), ferroelectric ceramics were fabricated from the natural sintering of powders prepared by the thermal decomposition of adequate precursor solutions. Their crystal structure was determined by x-ray diffraction, and the temperature dependence of dielectric constants were measured. The results show that KBT may be a kind of order–disorder relaxor ferroelectric with a first-order phase transition below the temperature of dielectric constant maximum.

Formation of drug/surfactant catanionic vesicles and their application in sustained drug release.

The aggregation behavior of the cationic drug/anionic surfactant vesicles formed by tetracaine hydrochloride (TH) and double-chain surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), was investigated. By controlling the molar ratio of TH to AOT, a transition from catanionic vesicles to micelles was observed. The catanionic aggregates exhibited different charge properties, structures, interaction enthalpies and drug release behaviors depending on the composition. To characterize the cationic drug/anionic surfactant system, transmission electron microscopy (TEM), dynamic light scattering (DLS), isothermal titration calorimetry (ITC), conductivity, turbidity and zeta potential (ζ) measurements were performed. The drug release results indicate that the present drug-containing catanionic vesicles have promising applications in drug delivery systems. Furthermore, the percentage of drug distributed in the catanionic vesicles or micelles can be obtained by comparing the cumulative release of the corresponding aggregates with the pure drug solution.

Sustained release of 5-fluorouracil by incorporation into sodium carboxymethylcellulose sub-micron fibers.

This work introduces a novel route to the sodium carboxymethylcellulose sub-micron fibers loaded with hydrophilic anticancer drug, 5-fluorouracil (5-Fu). The results show that 5-Fu is successfully incorporated into the biocompatible polymer, sodium carboxymethylcellulose (NaCMC)-based fibers with good stability, desired drug loading content and 100% entrapment efficiency. Furthermore, the drug release rate of the as-prepared drug-loaded fibers could be well controlled. The drug release behavior of the 5-Fu-loaded NaCMC fibers shows a diffusion mechanism, obeying Ritger-Peppas kinetics model. The drug release behavior of the as-prepared products demonstrates their promising application in drug delivery system.

Ibuprofen-loaded poly(lactic-co-glycolic acid) films for controlled drug release

Ibuprofen- (IBU) loaded biocompatible poly(lactic-co-glycolic acid) (PLGA) films were prepared by spreading polymer/ibuprofen solution on the nonsolvent surface. By controlling the weight ratio of drug and polymer, different drug loading polymer films can be obtained. The synthesized ibuprofen-loaded PLGA films were characterized with scanning electron microscopy, powder X-ray diffraction, and differential scanning calorimetry. The drug release behavior of the as-prepared IBU-loaded PLGA films was studied to reveal their potential application in drug delivery systems. The results show the feasibility of the as-obtained films for controlling drug release. Furthermore, the drug release rate of the film could be controlled by the drug loading content and the release medium. The development of a biodegradable ibuprofen system, based on films, should be of great interest in drug delivery systems.

Huperzine A-phospholipid complex-loaded biodegradable thermosensitive polymer gel for controlled drug release

The huperzine A-phospholipid complex loaded biodegradable thermosensitive PLGA-PEG-PLGA polymer gel was studied as injectable implant system for controlled release of huperzine-A (HA). First, HA molecules were successfully incorporated into the soybean phosphatidylcholine (SP) molecules to form the huperzine-A-soybean phosphatidylcholine complexes (HA-SPC), which was proved by FT-IR, DSC, XRD, solubility study, TEM, etc. The results indicated that hydrogen bonds and electrostatic interaction between HA and SP molecules play an important role in the formation of HA-SPC. Secondly, the HA-SPC was loaded into biodegradable PLGA-PEG-PLGA thermosensitive gel as injectable implant material to control the release of HA. The in vitro and in vivo drug release behaviors of the prepared products were studied. The in vitro release studies demonstrated that the HA-SPC-loaded gel significantly reduced the initial burst of drug release and extended the release period to about 2 weeks. The in vivo pharmacokinetics study of HA-SPC-loaded gel in rabbits showed that plasma concentration of HA (2.54-0.15ng/mL) was detected for nearly 2 weeks from delivery systems upon single subcutaneous injection. Whats more, the in vitro release pattern correlated well with the in vivo pharmacokinetics profile. The present study indicates that HA-SPC loaded PLGA-PEG-PLGA thermal gel may be an attractive candidate vehicle for controlled HA release.

Ionic liquid-assisted synthesis of SnO2 particles with nanorod subunits for enhanced gas-sensing properties

An ionic liquid-assisted synthetic route is proposed for the synthesis of SnO2 particles. Specifically, the SnO2 particles with nanorod subunits could be synthesized by the present route. The ionic liquid is found to play a key role in the formation of these interesting particles. This is the first time that these interesting structures have been reported. The formation mechanism for these interesting particles is investigated in detail. A gas-sensing analysis for the detection of various organic vapors shows that the sensors based on the synthesized SnO2 particles exhibit remarkable sensitivity, low detection limits and fast response/recovery times, which is attributed to their nanorod subunits.

Catanionic vesicles from an amphiphilic prodrug molecule: a new concept for drug delivery systems

Toxicity and low entrapment efficiency are the main problems for pharmaceutical applications of catanionic vesicles. In order to minimize surfactant toxicity, increase the drug loading content and simultaneously reduce the need for tedious chemical synthesis, we use oleic acid as the biocompatible surfactant, which reacts with the selected drug molecules (amlodipine) to produce an amphiphilic prodrug molecule for the straightforward fabrication of catanionic vesicles. The prodrug molecules are easily obtained by proton transfer between amlodipine and oleic acid molecules. The characterization of prodrug molecules and their aggregation behaviours in aqueous solutions are investigated by using Fourier transform infrared spectrophotometry (FTIR), 1H-nuclear magnetic resonance (1H-NMR), differential scanning calorimetry (DSC), surface tension measurement, transmission electron microscopy (TEM), dynamic light scattering (DLS), conductivity and zeta potential (ζ). The results demonstrate that vesicles could be easily formed with the prodrug amphiphilic molecules dispersed in aqueous solutions. Particularly, the drug release behaviour of the as-prepared catanionic vesicles exhibits excellent sustained drug release properties, which demonstrates their promising application in the newly designed drug delivery system.

In(OH)3 particles from an ionic liquid precursor and their conversion to porous In2O3 particles for enhanced gas sensing properties

The ionic liquid precursor tetrabutylammonium hydroxide (TBAH) is used to synthesize In(OH)3 particles. The ionic liquid TBAH is demonstrated to be effective for the synthesis of In(OH)3 nanorods with a controlled size. The effect of the indium salt and the added water amount on the final products is investigated. The synthesized In(OH)3 nanorods could be further transformed into porous In2O3 rod particles. Specifically, the gas sensing properties of the synthesized porous In2O3 rod particles to various organic compounds (methanol, ethanol, isopropanol, butanol, ethyl acetate and toluene) exhibit remarkable sensitivities, low detection limits and fast response–recovery times, which are superior to the reported In2O3 based sensors. The as-prepared porous In2O3 rod-based sensors thus demonstrate their potential applications in detecting chemical contaminants and dangerous gases.

Synthesis of ZnO particles on zinc foil in ionic-liquid precursors

Structurally similar ionic-liquid precursors are explored for the synthesis of ZnO nanoparticles on zinc foil. During the synthesis, the ionic-liquid precursors have multi-functions such as reactant, solvent and template. Experiments are performed at different ionic-liquid precursor concentrations. Results demonstrates that different ZnO nanostructures with uniform size and morphology can be synthesized from tetrabutylammonium hydroxide (TBAH), tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMAH) and benzyltrimethylammonium hydroxide (BTMAH) ionic-liquid precursors on the surface of zinc foil. The formation mechanism of the synthesized particles is proposed based on the experimental results.

Fine regulation of cellulose dissolution and regeneration by low pressure CO2 in DMSO/organic base: dissolution behavior and mechanism

In this study, the fine regulation of the dissolution and regeneration of microcrystalline cellulose (MCC) using very low pressure (0-0.2 MPa) CO2 in a mixed solvent of dimethyl sulfoxide (DMSO) and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) at a very low temperature (30 °C) was achieved. The solubility of MCC in DMSO/DBU (weight ratio of DMSO WDMSO = 0.90) could reach 9.0% at 30 °C and under CO2 pressure of 0.2 MPa. A similar phenomenon was observed in the mixed solvent DMSO/1,1,3,3-tetramethylguanidine (TMG). Moreover, ATR-FTIR, NMR, UV-Vis, TGA, XRD and DFT computational analyses were used to investigate the dissolution mechanism. It was concluded that in the mixed solvent (DMSO and organic base), DMSO helped to dissociate ion-pairs into free ions by balancing the concentration of free ions and the number of hydrogen bonds at WDMSO = 0.90. Interactions between CO2 and the solvent mixture were explored, and the results indicate that the optimum CO2 pressure not only promotes the formation of ionic bonds but also accelerates the formation of covalent bonds. In this way, these interactions prevent the MCC molecules from aggregating and facilitate the dissolving of MCC. This study gives a thorough insight into the dissolution mechanism and specificity of MCC in the CO2-DMSO/organic base solvent system, which could be helpful for the utilization and transformation of cellulose.