Wrinkled liquid-crystalline microparticle-enhanced photoresponse of PDLC-like films by coupling with mechanical stretching

Photoresponsive behaviors are studied in hybrid liquid-crystalline (LC) films prepared with light-responsive LC polymer microparticles as dopants using photoinert polymers as a host material. Upon mechanical stretching, both topological shape change and mesogenic alignment occur in the LC polymer microparticles, enabling the polymer-dispersed LC (PDLC)-like films to bend toward a light source upon UV irradiation. The rough morphologies of the hydrophobic LC microparticles enhance their interactions with hydrophilic polymer substrates. The bilayer-like structures of the hybrid film formed in the fabrication processes are responsible for the photomechanical behavior, which is reversibly controlled by combing light irradiation with the stretching processes.     

Fabrication of hydrophilic paclitaxel-loaded PLA-PEG-PLA microparticles via SEDS process

In this work, chemically bonded poly(D, L-lactide)-polyethylene glycol-poly(D, L-lactide) (PLA-PEG-PLA) triblock copolymers with various PEG contents and PLA homopolymer were synthesized via melt polymerization, and were confirmed by FTIR and ¹H-NMR results. The molecular weight and polydispersity of the synthesized PLA and PLA-PEG-PLA copolymers were investigated by gel permeation chromatography. Hydrophilicity of the copolymers was identified by contact angle measurement. PLA-PEG-PLA and PLA microparticles loaded with and without PTX were then produced via solution enhanced dispersion by supercritical CO₂ (SEDS) process. The effect of the PEG content on the particle size distribution, morphology, drug load, and encapsulation efficiency of the fabricated microparticles was also studied. Results indicate that PLA and PLA-PEG-PLA microparticles all exhibit sphere-like shape with smooth surface, when PEG content is relatively low. The produced microparticles have narrow particle size distributions and small particle sizes. The drug load and encapsulation efficiency of the produced microparticles decreases with higher PEG content in the copolymer matrix. Moreover, high hydrophilicity is found when PEG is chemically attached to originally hydrophobic PLA, providing the produced drug-loaded microparticles with high hydrophilicity, biocompatibility, and prolonged circulation time, which are considered of vital importance for vessel-circulating drug delivery system.     

Fabrication strategies and supramolecular interactions of polymer-lipid complex nanoparticles as oral delivery systems

Nano Research - Oral administration of nutrient/drug is the most common and preferred route. However, a number of barriers are encountered after ingestion, limiting efficient oral nutrient/drug...     

Fabrication of chitosan microparticles loaded in chitosan and poly(vinyl alcohol) scaffolds for tissue engineering application

In recent decades, the use of microparticle-mediated drug delivery is widely applied in the field of biomedical application. Here, we report the new dressing material with ciprofloxacin-loaded chitosan microparticle (CMP) impregnated in chitosan (CH) and poly(vinyl alcohol) (PVA) scaffold for effective delivery of drug in a sustained manner to the wound site. Moreover, the peculiar physiochemical and structural properties of the CH–CMP scaffold has proved better tensile strength and excellent swelling to achieve 82% of drug release. In vitro biocompatibility was done for both scaffold using NIH 3T3 fibroblasts and human keratinocytes (HaCaT) cell lines. In vitro fluorescent activity showed distinct biocompatibility with good cell adhesion and proliferation. However, the CH–CMP scaffold showed best result to act as promising biomaterial in effective drug delivery in tissue engineering.     

Enhanced visible-light photoresponse of DVT-grown Ni-doped SnSe crystal

Semiconductors with the group of IV-VI are key components of future photonics technology due to their unique properties. In the present study, we investigated the influence of nickel inclusion on the structural and electrical responsiveness of SnSe-layered crystals produced through direct vapour transport. The elemental composition, stoichiometry of grown crystals and the orthorhombic structure were investigated by EDAX and XRD analysis. The phase and high crystallinity of produced compounds are revealed by scanning electron microscopy and the SAED pattern of transmission electron microscopy. Nickel-doped SnSe photodetector exhibited a photocurrent of 53.83 nA, which is six times higher compared to the pristine SnSe. Moreover, the pristine and nickel-doped SnSe demonstrated excellent photoresponse behaviour under visible light. Additionally, important photodetection characteristics such as photoresponsivity (R), spectral detectivity (D), rise time and decay time are assessed. Our findings contribute to a better understanding of SnSe and Ni-doped SnSe-based photodetection capabilities which open up the future gateway for SnSe-based optoelectronic devices.

     

The multiscale spectral and spatial character of photoresponse in CdZnTe crystals

Experiments give evidence of the spectral and spatial instabilities of the photoresponse in CdZnTe crystals, which are caused by the transformation of fields created by ensembles of structural defects of various types and scales. Wavelet analysis of the photocurrent as a function of the light wavelength (I = f(λ)) and the spatial coordinate (I = f(x)) reveal a correlation between the spectral instability and the spatial arrangement of crystal regions where this instability arises.     

聚苯乙烯微球化学制备及镀镍工艺研究

在聚苯乙烯微球表面进行化学镀镍可以制备磁性微球.采用此方法,能将聚苯乙烯的轻质的优点和镍的磁性结合起来.同时,此方法还具有如下优点:操作简单、反应条件易于控制.采用扫描电镜(SEM)表征了微球的表面形貌.考察了施镀温度、镀液浓度、镀液pH值对结果的影响.     

Hierarchical approach to modelling of liquid-crystalline polymers

Summary Liquid-crystalline polymers exhibit fascinating structure at many size scales. This paper describes how computer models at different size scales can be linked together by a hierarchical approach to give a better understanding of the properties and behaviour of these materials. The atomic scale is considered first, where semi-empirical molecular orbital techniques are used to calculate the torsional energy functions associated with rotating the backbone bonds of the polymer. Secondly, entire chains are simulated using a Monte Carlo technique based on the torsional energy functions to deduce the persistence length of the polymer of interest. A theoretical relationship enables the Frank elastic constants to be determined from the persistence length. The elastic constants may then be used as input parameters for models both to predict microstructure and to help understand the role of defects in the shear flow of these materials. The hierarchical approach provides a meaningful framework within which data obtained from small-scale models are used to parameterise models at a larger scale.     

Molecular architecture and supramolecular chemistry

Recent developments in synthetic methods and supramolecular chemistry have led to well defined structures. New characterization techniques have helped to advance this field. Recent work highlights the interplay between molecular architecture and the processes of spontaneous and induced organization, which have led to the rational design of ordered molecular materials.     

花状微米颗粒的制备及其电流变性能研究

采用溶剂热法制备出花状微米颗粒。采用SEM,TEM,XRD,FT-IR等方法分析颗粒形貌及成分。结果表明,花状颗粒为丙三醇基化合物,其表观直径在2~3μm之间,表面由次级的刺状结构组成。分别以花状微米颗粒和光滑球状Ti O2颗粒为分散相制备电流变液,并测试其电流变性能和沉降稳定性。实验结果表明,在相同电场强度下,花状颗粒电流变液的剪切屈服强度明显高于光滑球状颗粒电流变液,但漏电流密度远小于光滑球状颗粒电流变液;静置12 d,花状颗粒电流变液的抗沉降率较之光滑球状颗粒电流变液有显著提高。花状颗粒特有的形貌是其具有优异电流变性能和沉降稳定性的主要原因。     

Preparation and characterization of heparin-loaded polymeric microparticles

Microparticles containing heparin were prepared by a water-in-oil-in-water emulsification and evaporation process with pure or blends of biodegradable (poly-epsilon-caprolactone and poly(D,L-lactic-co-glycolic acid)) and of positively-charged non-biodegradable (Eudragit RS and RL) polymers. The influence of polymers and some excipients (gelatin A and B, NaCl) on the particle size, the morphology, the heparin encapsulation rate as well as the in vitro drug release was investigated. The diameter of the microparticles prepared with the various polymers ranged from 80 to 130 microns and was found to increase significantly with the addition of gelatin A into the internal aqueous phase. Microparticles prepared with Eudragit RS and RL exhibited higher drug entrapment efficiency (49 and 80% respectively) but lower drug release within 24 h (17 and 3.5% respectively) than those prepared with PCL and PLAGA. The use of blends of two polymers in the organic phase was found to modify the drug entrapment as well as the heparin release kinetics compared with microparticles prepared with a single polymer. In addition, microparticles prepared with gelatin A showed higher entrapment efficiency, but a significant initial burst effect was observed during the heparin release. The in vitro biological activity of heparin released from the formulations affording a suitable drug release has been tested by measuring the anti-Xa activity by a colorimetric assay with a chromogenic substrate. The results confirmed that heparin remained unaltered after the entrapment process.     

Preparation and characterization of collagen-modified polylactide microparticles

To improve cytocompatibility of polylactide (PLA) and to obtain an injectable scaffold for tissue engineering, collagen-modified PLA (CPLA) microparticles were prepared. Poly-(α-methacrylic acid)-grafted PLA (PMAA-PLA) was obtained by photooxidization and UV induced polymerization. Suspension of PMAA-PLA microspheres with an average size of 172.8 ± 3.6 nm was prepared with solvent evaporation technique. CPLA microparticles were prepared by adding collagen acetic acid solution into PMAA-PLA microsphere suspension prepared above. FTIR spectrum of PMAA-PLA confirmed that PMAA had been grafted on PLA surface. Analytical results of FTIR, XPS, SEM, hematoxylin and eosin (HE) stained and zeta potential measurement showed that the CPLA microparticles obtained by modifying PMAA-PLA microspheres with collagen molecules uniformly have a microporous structure and a particle size of less than 100 μm. The CPLA microparticles were expected to be used as an injectable scaffold for tissue regeneration.     

Fabrication of Li2TiO3 spherical microparticles from TiCl4 by a classical, inorganic sol-gel route; characteristics and tritium release properties

Medium sized spherical particles of Li₂TiO₃ (with diameters below 100 m) can be fabricated by a classical, inorganic sol-gel process, from commercially available TiCl₄. Elaborated process consists of the following main steps: (1) dissolving of TiCl₄ in concentrated aqueous HCl; (2) formation of sol emulsion in 2-ethylhexanol-1 containing the surfactant SPAN-80 (EH); (3) gelation of emulsion drops by extraction of water with partially dehydrated EH; (4) impregnation of gel to Li : Ti molar ratio (MR) = 2; (5) thermal treatment at 1200°C. This temperature can be significantly lowered (to 750°C) by chemical treatment of chloride precursors (gels or starting solution TiCl₄) with aq. ammonia or better with nitric acid. Tritium release from sol-gel made Li₂TiO₃ micro-spheres were found very close to that observed for other traditional materials, however for the first sample process starts slightly earlier.     

Sustained release of methotrexate through liquid-crystalline folate nanoparticles

To make chemotherapy more effective, sustained release of the drug is desirable. By controlling the release rates, constant therapeutic levels can be achieved which can avoid re-administration of drug. This helps to combat tumors more effectively with minimal side effects. The present study reports the control release of methotrexate through liquid-crystalline folate nanoparticles. These nanoparticles are composed of highly ordered folate self-assembly which encapsulate methotrexate molecules. These drug molecules can be released in a controlled manner by disrupting this assembly in the environment of monovalent cations. The ordered structure of folate nanoparticles offers low drug losses of about 4–5 %, which is significant in itself. This study reports the size-control method of forming methotrexate encapsulated folate nanoparticles as well as the release of methotrexate through these nanoparticles. It has been demonstrated that methotrexate release rates can be controlled by controlling the size of the nanoparticles, cross-linking cation and cross-linking concentration. The effect of different factors like drug loading, release medium, and pH of the medium on methotrexate release rates was also studied.