Design and fabrication of poly (glycerol sebacate)‐based fibers for neural tissue engineering: Synthesis,electrospinning, and characterization

Poly (glycerol sebacate) (PGS) is a thermoset biodegradable elastomer considered as a promising candidate material for nerve applications. However, PGS synthesis is very time and energy consuming. In this study, the PGS pre‐polymer (pPGS) was synthesized using three synthesis times of 3, 5, and 7 hours at 170°C. Fourier transform infrared (FTIR), nuclear magnetic resonance spectroscopy, X‐ray diffraction analysis, and differential scanning calorimetry thermogram were utilized to study the pPGS behavior. Poly (vinyl alcohol) was used as a carrier to fabricate aligned poly (vinyl alcohol)‐poly (glycerol sebacate) (PVA‐PGS) fibers with various ratios (60:40, 50:50, and 40:60) using electrospinning and crosslinked through the thermal crosslinking method. Morphology of the fibers was studied before and after crosslinking using scanning electron microscopy (SEM). FTIR, mechanical properties in the dry and wet state, water contact angle, in vitro degradation, and water uptake behavior of crosslinked scaffolds were also investigated. 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, SEM analysis, and 4′, 6‐diamidino‐2‐phenylindole (DAPI) staining were utilized to determine the biocompatibility of scaffolds. The results show the synthesized pPGS in 3 hours at 170°C is the optimized sample in the terms of chemical reaction. All scaffolds have bead‐free and a uniform fiber diameter. The Young's modulus of crosslinked PVA‐PGS (50:50 and 40:60) fibers is shown to be in the expected range for nerve applications. The cell culture studies reveal PVA‐PGS (50:50 and 40:60) fibers could lead to better cell adhesion and proliferation. The results suggest that PVA‐PGS (50:50 and 40:60) is a suitable and promising biodegradable material in the fabrication of scaffolds for nerve regeneration.     

改性海藻酸钠聚集行为对电纺纳米纤维形貌的影响

以过硫酸钾(KPS)为引发剂, 采用双丙酮丙烯酰胺(DAA)对海藻酸钠(SA)进行改性, 制备了海藻酸钠-聚双丙酮丙烯酰胺两亲性共聚物(SA-PDAA). 将SA-PDAA与聚乙烯醇(PVA)复配, 并进行静电纺丝, 制得SA-PDAA/PVA电纺纳米纤维. 通过红外光谱、 差示扫描量热和荧光光谱表征了SA-PDAA的结构和性能, 通过黏度仪、 表面张力仪和电导率仪测试了SA-PDAA纺丝液的物理性能, 用扫描电子显微镜表征了SA-PDAA/PVA电纺纳米纤维的形貌, 考察了SA-PDAA/PVA电纺纳米纤维的释药性能. 结果表明, DAA接枝到SA分子链上, SA-PDAA的临界聚集浓度为0.072 g/L, SA-PDAA具有良好的两亲性, SA-PDAA/PVA电纺纳米纤维具有均一的形貌. 改性后的SA可以有效地减缓药物释放速度, 提高SA-PDAA/PVA电纺纳米纤维的缓释性能.     

Preparation of porous nanocomposite scaffolds with honeycomb monolith structure by one phase solution freezedrying method

Biodegradable porous nanocomposite scaffolds of poly（lactide-co-glycolide）（PLGA） and L-lactic acid（LAc） oligomer surface-grafted hydroxyapatite nanoparticles（op-HA） with a honeycomb monolith structure were fabricated with the single-phase solution freeze-drying method.The effects of different freezing temperatures on the properties of the scaffolds,such as microstructures,compressive strength,cell penetration and cell proliferation were studied.The highly porous and well interconnected scaffolds with a tunable pore structure were obtained.The effect of different freezing temperature（4℃,-20℃,-80℃and -196℃） was investigated in relation to the scaffold morphology,the porosity varied from 91.2%to 83.0%and the average pore diameter varied from（167.2±62.6）μm to（11.9±4.2）μm while theσ₁₀ increased significantly.The cell proliferation were decreased and associated with the above-mentioned properties.Uniform distribution of op-HA particles and homogeneous roughness of pore wall surfaces were found in the 4℃frozen scaffold.The 4℃frozen scaffold exhibited better cell penetration and increased cell proliferation because of its larger pore size,higher porosity and interconnection.The microstructures described here provide a new approach for the design and fabrication of op-HA/PLGA based scaffold materials with potentially broad applicability for replacement of bone defects.     

Fabrication,rheological analysis,and in vitro characterization of in situ chemically cross‐linkable thermogels as controlled and prolonged drug depot for localized and systemic delivery

5‐Fluorouracil (5‐FU) is widely used against many types of solid cancer in clinics. However, because of its limitations such as short half‐life, poor oral absorption and rapid clearance by dihydropyrimidine dehydrogenase have limited its applications. In current study, new in situ chemically grafted thermogels for prolonged drug release are formed on the basis of poloxamer 407 (PF127) and carboxymethyl chitosan (CMCS) using glutaraldehyde as cross‐linking agent. The phase transition from sol to gel state at body temperature was confirmed by tube titling, rheological analysis, and optical transmittance determinations. Swelling and drug release experiments conducted at various pH and temperature demonstrated that developed formulations are thermoresponsive with maximum swelling and release below critical gelation temperature (CGT) (pH 7.4, 25°C). Cells growth inhibition study confirmed the biocompatibility of thermogels against L929 cell lines. Methyl thiazolyl tetrazolium (MTT) assay confirmed that 5‐FU–loaded thermogels have the potential to cause cells death against HeLa and MCF‐7 cancer lines. The IC₅₀ values calculated for pure 5‐FU solution (27 ± 0.81 μg/mL for HeLa and 24 ± 0.58 μg/mL for MCF‐7) were found higher in comparison with 5‐FU–loaded thermogels, against HeLa (17 ± 0.39 μg/mL) and MCF‐7 (14 ± 0.67 μg/mL). Fourier transform infrared (FTIR) confirmed the new structure formation and chemical grafting between PF127 and CMCS. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses proved the phase transition around physiologic temperature range, while scanning electron microscopy (SEM) analysis displayed the presence of connected pores in the cross section of thermogels facilitating the uptake of solvents and drug particles. Altogether, results concluded that developed chemically grafted thermogels can be used in vivo for prolonged drug release after subcutaneous administration.     

Bio‐based high‐performance waterborne hyperbranched polyurethane thermoset

Tannic‐acid‐based low volatile organic compound‐containing waterborne hyperbranched polyurethane was prepared. In order to improve the performance, it was modified in an aqueous medium using a glycerol‐based hyperbranched epoxy and vegetable‐oil‐based poly(amido amine) at different wt%. The combined system was cross‐linked by heating at 100°C for 45 min. Fourier transform infrared spectroscopy and swelling study were used to confirm the curing. A dose‐dependent improvement of properties was witnessed for the thermoset. Thermoset with 30 wt% epoxy showed excellent improvements in mechanical properties like tensile strength (~3.4 fold), scratch hardness (~2 fold), impact resistance (~1.3 fold), and toughness (~1.7 fold). Thermogravimetric analysis revealed enhancement of thermal properties (maximum 70°C increment of degradation temperature and 8°C increment of T_g). The modified system showed better chemical and water resistance compared with the neat polyurethane. Biodegradation study was carried out by broth culture method using Pseudomonas aeruginosa as the test organism. An adequate biodegradation was witnessed, as evidenced by weight loss profile, bacterial growth curve, and scanning electron microscope images. The work showed the way to develop environmentally benign waterborne polyurethane as a high‐performance material by incorporating a reactive modifier into the polymer network. Use of benign solvent and bio‐based materials as well as profound biodegradability justified eco‐friendliness and sustainability of the modified system. Copyright © 2015 John Wiley & Sons, Ltd.     

Carbendazim‐loaded electrospun poly(vinyl alcohol) fiber mats and release characteristics of carbendazim therefrom

Ultra‐fine poly(vinyl alcohol) (PVA) electrospun fiber mats containing carbendazim were successfully fabricated by electrospinning from the neat PVA solution containing carbendazim in various amounts based on the weight of PVA. The morphological appearance of both the neat and the carbendazim‐loaded electrospun PVA fibers were smooth and the incorporation of carbendazim in the neat PVA solution did not affect the morphology of the resulting fibers. The average diameters of the neat and the carbendazim‐loaded electrospun PVA fibers ranged between 155 and 160 nm. The chemical integrity of the as‐loaded carbendazim in the carbendazim‐loaded electrospun PVA fiber mats was intact as verified by the ¹H‐nuclear magnetic resonance spectroscopy. Thermal properties of the carbendazim‐loaded electrospun PVA fiber mats were analyzed by differential scanning calorimetry and thermogravimetric analysis. The release characteristics of the carbendazim‐loaded electrospun PVA mats were investigated by the total immersion method in distilled water at 30°C. The carbendazim‐loaded electrospun PVA mats exhibited greater amount of carbendazim released than the carbendazim‐loaded as‐cast films. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,self‐assembly,drug‐release behavior,and cytotoxicity of triblock and pentablock copolymers composed of poly(ε‐caprolactone), poly(L‐lactide), and poly(ethylene glycol)

Biocompatible and biodegradable ABC and ABCBA triblock and pentablock copolymers composed of poly(ε‐caprolactone) (PCL), poly(L ‐lactide) (PLA), and poly(ethylene glycol) (PEO) with controlled molecular weights and low polydispersities were synthesized by a click conjugation between alkyne‐terminated PCL‐b‐PLA and azide‐terminated PEO. Their molecular structures, physicochemical and self‐assembly properties were thoroughly characterized by means of FT‐IR, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, dynamic light scattering, and transmission electron microscopy. These copolymers formed microphase‐separated crystalline materials in solid state, where the crystallization of PCL block was greatly restricted by both PEO and PLA blocks. These copolymers self‐assembled into starlike and flowerlike micelles with a spherical morphology, and the micelles were stable over 27 days in aqueous solution at 37 °C. The doxorubicin (DOX) drug‐loaded nanoparticles showed a bigger size with a similar spherical morphology compared to blank nanoparticles, demonstrating a biphasic drug‐release profile in buffer solution and at 37 °C. Moreover, the DOX‐loaded nanoparticles fabricated from the pentablock copolymer sustained a longer drug‐release period (25 days) at pH 7.4 than those of the triblock copolymer. The blank nanoparticles showed good cell viability, whereas the DOX‐loaded nanoparticles killed fewer cells than free DOX, suggesting a controlled drug‐release effect. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Influence of graphene oxide incorporation and chemical cross‐linking on structure and mechanical properties of layer‐by‐layer assembled poly(Vinyl alcohol)‐Laponite free‐standing films

Functional fillers in multilayered films provide opportunity in tailoring the mechanical properties through chemical cross‐linking. In this study, Laponite‐graphene oxide co‐dispersion was used to incorporate graphene oxide (GO) easily into polyvinyl alcohol (PVA)/Laponite layer‐by‐layer (LBL) films. The LBL films were found to be uniform and the layer thickness increased linearly with number of depositions. The process was extended to a large number of depositions to investigate the macroscopic mechanical properties of the free‐standing films. The LBL films showed remarkable improvements in mechanical properties as compared to neat PVA film. The GO‐incorporated LBL films displayed higher enhancements in the tensile strength, ductility, and toughness as compared to that of PVA/Laponite LBL films, upon chemical cross‐linking. This suggests the advantageous effects of GO incorporation. Interestingly, cross‐linking of LBL films for longer time period (>1 h) and higher temperature (～80 °C) was not found to be much beneficial. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2377–2387     

The controlled release behavior and pH‐ and thermo‐sensitivity of alginate/poly(vinyl alcohol) blended hydrogels

Poly(vinyl alcohol) (PVA) was blended with sodium alginate (Alg) in various ratios and crosslinked with calcium chloride and made into hydrogel membranes. The dependence of the swelling behavior of these Alg‐Ca/PVA hydrogels on pH was investigated. The temperature‐dependent swelling behavior of the semi‐interpenetrating network (semi‐IPN) hydrogels was examined at temperatures from 2 to 45°C and the enthalpy of mixing (ΔH_mix) was determined at various temperatures. The molecular structure of the hydrogels was studied by infrared spectroscopy and their water structure in the semi‐IPN hydrogels was measured by differential scanning calorimetry (DSC). The influence of Ca²⁺ content on the network structure of Alg‐Ca/PVA hydrogels was investigated in terms of the compressive elastic modulus, effective crosslinking density, and the polymer–solvent interaction parameter based on the Flory theory. The loading of alizarin red S (ARS) followed the Langmuir isotherm mechanism and the release kinetics of ARS from the Alg‐Ca/PVA hydrogels followed the Fickian diffusion mechanism. Copyright © 2008 John Wiley & Sons, Ltd.     

Redox‐responsive core cross‐linked micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) by Diels‐Alder reaction for doxorubicin release

Redox‐responsive core cross‐linked (CCL) micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) (PEO‐b‐PFMA) block copolymers were prepared by the Diels‐Alder click‐type reaction. First, the PEO‐b‐PFMA amphiphilic block copolymer was synthesized by the reversible addition‐fragmentation chain transfer polymerization. The hydrophobic blocks of PFMA were employed to encapsulate the doxorubicin (DOX) drug, and they were cross‐linked using dithiobismaleimidoethane at 60 °C without any catalyst. Under physiological circumstance, the CCL micelles demonstrated the enhanced structural stability of the micelles, whereas dissociation of the micelles took place rapidly through the breaking of disulfide bonds in the cross‐linking linkages under reduction environment. The core‐cross‐linked micelles showed fine spherical distribution with hydrodynamic diameter of 68 ± 2.9  nm. The in vitro drug release profiles presented a slight release of DOX at pH 7.4, while a significant release of DOX was observed at pH 5.0 in the presence of 1,4‐dithiothreitol. MTT assays demonstrated that the block copolymer did not have any practically cytotoxicity against the normal HEK293 cell line while DOX‐loaded CCL micelles exhibited a high antitumor activity towards HepG2 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3741–3750     

Dual crosslinked pH‐ and temperature‐sensitive hydrogel beads for intestine‐targeted controlled release

Novel drug‐loaded hydrogel beads for intestine‐targeted controlled release were developed by using pH‐ and temperature‐sensitive carboxymethyl chitosan‐graft‐poly(N,N‐diethylacrylamide) (CMCTS‐g‐PDEA) hydrogel as carriers and vitamin B₂ (VB₂) as a model drug. The hydrogel beads were prepared based on Ca²⁺ ionic crosslinking in acidic solution and formed dual crosslinked network structure. The structure of hydrogel and morphology of drug‐loaded beads were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The study about swelling characteristics of hydrogel beads indicated that the beads had obvious pH‐ and temperature‐sensitivity. In vitro release studies of drug‐loaded beads were carried out in pH 1.2 HCl buffer solution and pH 7.4 phosphate buffer solution at 37°C, respectively. The results indicated that the dual crosslinked method could effectively control the drug release rate under gastrointestinal tract (GIT) conditions, which was superior to traditional single crosslinked beads. In addition, the effects of grafting percentage, pH value, and temperature on the release behavior of the VB₂ were investigated. The drug release mechanism of CMCTS‐g‐PDEA drug‐loaded beads was analyzed by Peppa's potential equation. According to this study, the dual crosslinked hydrogel beads based on CMCTS‐g‐PDEA could serve as suitable candidate for drug site‐specific carrier in intestine. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and properties of water‐soluble chitosan and polyvinyl alcohol blend films as potential bone tissue engineering matrix

The blend film was prepared by casting solutions of water‐soluble hydroxyethyacryl‐chitosan (HEA‐CS) and polyvinyl alcohol (PVA) and cross‐linked by glutaraldehyde. The structure and properties of the blend films were estimated by wide‐angle X‐ray diffraction (WXRD), contact angle measurements with water, and scanning electron microscopy (SEM). The tensile properties of the blend films were investigated and the tensile strength (TS) and the elongation increased with the increased amount of PVA. The thermal stability (thermogravimetric (TG) and derivative thermogravimetric (DTG)) was evaluated and HEA‐CS was more thermally‐stable than that of PVA. The water swelling properties analysis indicated that HEA‐CS in the blends promoted the water absorption owing to its porous structure and the antimicrobial ability of the blend films was retained. Indirect cytotoxicity assessment of the blend films with human bone sarcoma cell (SW1353) indicated that the biomaterials were non‐toxic and did not release substances harmful to living cells. Copyright © 2009 John Wiley & Sons, Ltd.     

Conducting films of poly(aniline‐co‐1‐amino‐ 2‐naphthol‐4‐sulfonic acid) blended with LDPE for its application as antistatic encapsulation material

The paper presents the electrostatic charge dissipative (ESD) properties of the conducting copolymers of aniline (AN) and 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) blended with low‐density polyethylene (LDPE). The copolymers of aniline and ANSA were synthesized under different reaction conditions. Blending of copolymers with LDPE was carried out in twin screw extruder by melt blending method by loading 0.5 and 1.0 wt% of the conducting copolymer in LDPE matrix. The mechanical properties of the blended films depend on the incorporation of copolymer in the LDPE matrix. The morphology of copolymer–LDPE blend was studied by scanning electron microscopy. The conductivity of the blown film of poly(AN‐co‐ANSA)/LDPE blend was found to be in the range of 10^?6–10^?11 S/cm, showing its potential use as antistatic bag for the encapsulation of electronic equipments. The static decay time of the film was found to be of the order of 0.1–1.9 sec on recording the decay time from 5000 to 500 V. Static charge measurements carried out on the films show that no charge is present on the surface. The level of interaction between the copolymers and the matrix polymer was determined by the FTIR spectra, blend morphology, electrical conductivity, and thermal analysis. The effect of the morphology on electrical and antistatic behavior of copolymers has also been investigated. Copyright © 2009 John Wiley & Sons, Ltd.     

Manipulating the degradation rate of PVA nanoparticles by a novel chemical‐free method

The high water solubility of poly (vinyl alcohol) (PVA) is one of the challenging problems in its application. In order to rectify this problem, PVA needs to be crosslinked. Freeze‐thawing in solid state as a novel physical crosslinking method was employed for enhancement the stability of PVA nanoparticles in aqueous solutions during this study. PVA nanoparticles were successfully prepared by electrospraying and electrospray conditions were optimized in the view points of polymer concentration and solvent system. The morphology of nanoparticles was tailored from collapsed particles and mixture of particles/fibers to spherical particle by manipulating of polymer solution concentration and solvent system. After preparation of PVA nanoparticles in optimum condition, they were frozen at ?20°C and subsequently thawed at 25°C for different cycles of 1, 2, and 3. Field‐emission scanning electron microscope (FE‐SEM), Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimeter (DSC), and biodegradation were used to evaluate the effect of freeze‐thawing on properties of PVA nanoparticles. FE‐SEM showed the spherical morphology of the PVA nanoparticles with sizes ranging from 200 to 300 nm. The FTIR spectroscopy indicated that the crystallinity of PVA nanoparticles increases after freeze‐thawing process. Moreover, by increasing the number of cycles, degree of crystallinity of nanoparticles increases. The XRD and DSC analysis of PVA nanoparticles again demonstrated the increasing of crystallinity of nanoparticles after freeze‐thawing process. The biodegradation behavior of PVA nanoparticles after freeze‐thawing exhibited the decreasing of degradation rate by increasing the number of cycles. Our overall results present a solvent‐less and safe method for crosslinking of PVA nanoparticles in solid state, which make it suitable for biomedical applications.     

PVA‐encapsulated Palladium Nanoparticles: Eco‐friendly and Highly Selective Catalyst for Hydrogenation of Nitrobenzene in Aqueous Medium

In aqueous medium without any other additives, palladium (Pd) nanoparticles with water‐soluble polyvinyl alcohol (PVA) as stabilizer were synthesized for the catalytic hydrogenation of nitrobenzene. Under the optimum experimental conditions, the nitrobenzene conversion and the selectivity for aniline were 99.3 % and 100 %, respectively. Comprehensive characterization methods, including TEM, UV/Vis, confocal laser scanning microscopy (CLSM), XRD and XPS allowed a better understanding of the role of PVA aggregates and the properties of Pd nanoparticles. The nitrobenzene conversion exceeded 80 % even after 6 cycles without any treatment of the catalyst. A mechanism about the hydrogenation of nitrobenzene catalyzed by Pd/PVA system was proposed. The Pd/PVA catalyst also exhibited excellent activity and selectivity, particularly to ortho‐fluoronitrobenzene and ortho‐nitrotoluene. This research can provide a reference for the environmentally friendly catalysis for hydrogenation of nitrobenzene and other substituted nitrobenzene compounds.     

In vitro biocompatibility of three‐dimensional chitosan scaffolds immobilized with chondroitin‐6‐sulfate

Cellular‐compatible scaffolds were prepared using a three‐dimensional micro‐porous chitosan (CS) non‐woven fabric immobilized by glutaraldehyde (GA), followed by the immobilization of chondroitin‐6‐sulfate (ChS). To characterize the immobilizing process, tensile analysis, and scanning electron microscopy (SEM) were performed. The cell seeding efficiency and proliferation test were evaluated using L929 fibroblasts. The chitosan scaffolds showed high water vapor transmission rate and antibacterial activity. In addition, ChS‐immobilized scaffolds exhibited higher cell seeding efficiency and fibroblasts proliferation. These results demonstrated that the CS non‐woven fabrics grafted with GA and immobilized with ChS could be an appropriate candidate for wound healing and artificial scaffolds in the clinical applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Gelatin-coated gold nanoparticles as an effective pH-sensitive methotrexate drug delivery system for breast cancer treatment

The present study investigates the synthesis and effectiveness of gold/gelatin nanoparticles (NPs) biopolymer as a carrier for methotrexate (MTX) drug. Two different shapes of gold particles, including spherical AuNPs (50 & 100 nm) and gold nanorods (AuNRs) with three different sizes (20, 50 and 100 nm length) were synthesized using the chemical reduction method. The effect of AuNPs size and shape on the entrapment efficiency (E.E), the release rate of the drug, and cellular uptake were investigated. The surfaces of both AuNPs and AuNRs were coated with a gelatin biopolymer, and the stability and property of the generated compounds were studied. Moreover, MTX as a chemotherapeutic agent was loaded on the gelatin-coated AuNPs/AuNRs complexes. The physicochemical properties of the gelatin-coated AuNPs/AuNRs complexes were studied using ultraviolet-visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The E.E and MTX release behavior from the complexes at pH values of 7.4 and 5.4 and temperatures of 37 and 40 °C were investigated in vitro. The cytotoxic effects of AuNPs, AuNPs-Gelatin, AuNPs-Gelatin-MTX, AuNRs, AuNRs-Gelatin, AuNRs-Gelatin-MTX and free MTX were studied. The results indicated that the E.E of AuNPs was higher than that of AuNRs. The highest release rate of the drug was related to the AuNR1-gelatin complex (pH 5.4 and temperature of 40 °C). In addition, MTX loaded AuNR2-gelatin showed the highest cytotoxic effect on the MCF-7 breast cancer cell line so that even its cell cytotoxicity was more than that of the free drug.     

Novel nano molten salt tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide as a vanadium surface‐free phthalocyanine catalyst: Application to Strecker synthesis of α‐aminonitrile derivatives

Efficient and recyclable novel nano tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide, {[VO(TPPA)][C(CN)₃]₄}, as a vanadium surface‐free phthalocyanine‐based molten salt catalyst was successfully designed, produced and used for the Strecker synthesis of α‐aminonitrile derivatives through a one‐pot three‐component reaction between aromatic aldehydes, trimethylsilyl cyanide and aniline derivatives under neat conditions at 50 °C. This catalyst was well characterized using Fourier transform infrared, UV–visible, X‐ray photoelectron and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, scanning and high‐resolution transmission electron microscopies, inductively coupled plasma mass spectrometry and thermogravimetric analysis. The catalyst can be simply recovered and reused several times without significant loss of catalytic activity.     

Thermal,morphological, and mechanical properties of ethyl vanillin immobilized in polyvinyl alcohol by electrospinning process

In this study, polyvinyl alcohol (PVA) nanofibers with ethyl vanillin as an active compound were prepared using electrospinning technique. The final products of electrospinning process were in the form of nanofibers films. PVA/ethyl vanillin nanofibers, having fibers diameters in the range 100–1700 nm, were successfully electrospun from ethanol/water mixture of PVA and ethyl vanillin. The effects of immobilization process on ethyl vanillin thermal properties were investigated by differential scanning calorimetry (DSC). The results of DSC showed significant influence of immobilization process on thermal properties of ethyl vanillin. It was noticed that melting point of immobilized ethyl vanillin was lower (~55 °C) compared to free flavor (~77 °C). Our results showed that films based on PVA/ethyl vanillin nanofibers are mechanically stable.     

A pH‐sensitive water‐soluble N‐carboxyethyl chitosan/poly(hydroxyethyl methacrylate) hydrogel as a potential drug sustained release matrix prepared by photopolymerization technique

Biocompatible pH‐sensitive semi‐interpenetration polymeric network hydrogels (semi‐IPN) based on water‐soluble N‐carboxyethyl chitosan (CECS) and 2‐hydroxyethyl methacrylate (HEMA) were synthesized by the photopolymerization technique. pH‐sensitivity, cytotoxicity, morphology, mechanical property, and water state of hydrogel were investigated by a swelling test, methylthiazolydiphenyl‐tetrazolium bromide (MTT) assay, scanning electron microscopy (SEM), universal testing machine, and differential scanning calorimetry (DSC), respectively. The drug release studies were carried out using 5‐Flurouracil as the model drug. The results indicated that the hydrogels were sensitive to pH of the medium and its wet state had good mechanical properties. The results of cytotoxicity and prolonged drug release characteristics revealed the suitability of the hydrogels as drug delivery matrices. The release kinetics was evaluated by fitting the experimental data to standard release equations, and the best fit was obtained with the Higuchi model of the hydrogel. Copyright © 2008 John Wiley & Sons, Ltd.