An investigation on the properties of SnO2 nanoparticles synthesized using two different methods

Tin oxide SnO₂ nanoparticles have been synthesized using chemical co-precipitation and solvothermal methods. The structures and morphologies of SnO₂ prepared using both routes were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier infrared absorption spectroscopy (FT-IR), UV–Vis Spectroscopy and BET specific surface area. The XRD patterns showed the presence of the tetragonal structure in the nanometric range and both crystallinity as well as crystal size increased with the increasing in temperature. The size of the produced tin dioxide nanoparticles was from 6.2 to 10.6 nm by solvothermal route while it was from 9.3 to 16.2 nm for nanoparticles by co-precipitation pathway. Furthermore, TEM results showed that the sizes of SnO₂ particles in all powders were tetragonal like structure and the grain size was increased with temperature. FT-IR spectra revealed that intensity of the transverse optical mode of Sn–O stretching vibration was increased with the sintering temperature while the bending vibration of O–Sn–O showed a blue shift. The optical band gap was shifted to a lower energy with increasing temperature due to the improvement of the crystallinity and the value was varied from 2.9 to 4.25 eV. The specific surface area of the as-made SnO₂ in comparison with such calcined samples decreased with increasing the calcination temperature due to the changes in the sample particle size and in the sample crystal phases.     

Silk fibroin-based woven endovascular prosthesis with heparin surface modification

A novel seamless silk fibroin-based endovascular prosthesis (SFEPs) with bifurcated woven structure and anticoagulant function for the improvement of patency is described. The SFEPs were prepared from silk fibroin (SF) and polyester filaments using an installed weaving machine. The production processing parameters were optimized using orthogonal design methods. The inner surface of SFEPs was modified with polyethylenimine (PEI) and EDC/NHS-activated low-molecular-weight heparin (LMWH) to enhance anticoagulant function. The surface morphology and mechanical properties of the SFEPs were evaluated according to standard protocols. The thickness of modified SFEPs was lower than 0.085?±?0.004?mm and water permeability was lower than 5.19?±?0.30?mL/(cm²?×?min). The results of mechanical properties showed that the diametral tensile strength and burst strength reached 61.6?±?1.8 and 23.7?±?2.2?MPa, respectively. Automatic coagulometer and energy-dispersive X-ray (EDX) confirmed LMWH immobilization on the surface of the SFEPs and the blood compatibility was improved with the heparin modification with PEI polymerization. In conclusion, the new prosthesis has potential applications in the blood vessel repairs where minimal thickness but superior mechanical strength and biocompatibility are important.     

Polymeric micelles comprising stearic acid-grafted polyethyleneimine as nonviral gene carriers

Non-viral vectors composed of biodegradable polymers or lipids have been considered as a safer alternative for gene carriers over viral vectors. Among some of the cationic polymers, polyethyleneimine (PEI) possess high pH-buffering capacity that can provide protection to nucleotides from acidic degradation and promotes endosomal and lysosomal release. However, it has been reported that cytotoxicity of PEI depends on the molecular weight of the polymer. Hence modifications of PEI structure for clinical application have been developed in order to reduce the cytotoxicity, or improve the insufficient transfection efficiency of lower molecular weight PEI. In this study, 10 k PEI was modified by grafting stearic acid (SA) and formulated to polymer micelles with positive surface charge and evaluated for pDNA delivery. The amine group on PEI was crosslinked with the carboxylic group of stearic acid by 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDC) as linker. PEI-SA micelles were then prepared using oil in water (o/w) solvent evaporation method. The success of PEI-SA conjugation structure was confirmed with 1H NMR. The average diameter and zeta potential determined by photon correlation spectroscopy was 149.6 +/- 1.2 nm and 64.1 +/- 1.5 mV, respectively. These self-assemble positive charge micelles showed effective binding to pDNA for transfection. PEI-SA micelles exhibited lower cytotoxicity compared to that of PEI only, while flow cytometry analysis revealed PEI-SA/pEGFP complex provided 62% high EGFP expression. Luciferase activity also showed high transfection efficiency of PEI-SA micelles for weight ratio above 4.5 that was comparable to PEI only. These results demonstrated that stearic acid grafted PEI micelles can provide high transfection efficiency comparable to unmodified PEI, and exhibit low cytotoxicity. Stearic acid grafted PEI micelles can be promising polymer carriers in genetic therapy.     

EDC/NHS交联改性再生桑蚕丝素纳米纤维

用静电纺丝技术制备了再生桑蚕丝素纳米纤维,并用1-(3-二甲基氨基丙基)-3-乙基碳化二亚胺(EDC)和N-羟基丁二酰亚胺(NHS)进行交联改性,考察了交联改性前后,桑蚕丝素纳米纤维微观形貌及聚集态结构等的变化,采用扫描电镜(SEM)、X射线衍射(XRD)及红外光谱(FT-IR)等测试方法对纳米纤维进行表征。研究结果表明,经EDC/NHS交联改性后,纤维直径由250 nm增加到320 nm,纤维表面变粗糙,且纤维发生弯曲变形;丝素的结构以Silk II为主,并含有部分无规卷曲或Silk I构象;桑蚕丝纳米纤维的力学性能和亲水性有所提高,且交联改性后的纳米纤维具有良好的细胞相容性。     

Novel supramolecular hydrogels made via Michael-type addition reaction of dithiothreitol with self-assembly of α-cyclodextrins and acryloyl-terminated 3-arm PEG

A kind of novel three-dimensional crosslinked hydrogel was synthesized via Michael-type addition reaction of dithiothreitol (DTT) as a crosslinker/extender towards the self-assembly of α-cyclodextrins (α-CDs) with acryloyl end capped 3-arm PEG. The supramolecular structure of the resulting hydrogels was characterized by using FT-IR, TGA, XRD and DSC measurements. The effect of varying the amount of α-CDs was studied on the crosslinking process. Interestingly, this conjugation reaction is smoothly carried out at physiological temperature and pH in the absence of any sensitizer or catalyst. It appears that these chemically crosslinked hydrogels have the potential to be used as carriers for drug controlled release and scaffolds for injectable tissue engineering.     

Low temperature aqueous precipitation of needle-like nanophase hydroxyapatite

The use of tissue engineered biodegradable porous scaffolds has become an important focus of the biomedical research field. The precursor materials used to form these structures play a vital role in their overall performance thus making the study and synthesis of these selected materials imperative. The authors present a comparison and characterisation of hydroxyapatite (HA), a popular calcium phosphate (CaP) biomaterial, synthesised by an aqueous precipitation (AP) method. The influence of various reaction conditions on the phase, crystallinity, particle size as well as morphology, molecular structure, potential in-vivo bioactivity and cell viability were assessed by XRD, SEM and TEM, FTIR, a simulated body fluid (SBF) test and a live/dead assay using MC3T3 osteoblast precursor cells, respectively. Naturally carbonated nanoparticles of HA with typically needle-like morphology were synthesised by the reported AP method. Initial pH was found to influence the crystallisation process and determine the CaP phase formed as well as the resultant particle and crystallite sizes. A marked change in particle morphology was also observed above pH 9. The use of toluene as a replacement solvent for water up to 60 % was found to reduce the crystallinity of as-synthesised HA. This has marked influence on the effect of ethanolamine (5 wt%), which was found to improve HA crystallinity. SEM and EDS were used to confirm the growth of carbonated apatite on the surface of HA pellets immersed in SBF for up to 28 days. Cell culture results revealed viable cells on all samples where pH was controlled and maintained at 10–11 during precipitation, including those that used ethanolamine and toluene in preparation. When the initial alkali pH was not maintained non-viable cells were observed on HA substrates.     

DMPA含量对具有软段结晶性水性聚氨酯性能的影响

采用预聚体分散法,以DMPA作为亲水性单体,合成了一系列具有软段结晶性水性聚氨酯乳液(WPU)。通过FT-IR、粒径测量仪、接触角测量仪、XRD等对乳液性能和涂膜性能进行了表征。实验结果表明:乳液的粒径随DMPA含量的增加而减小,zeta电位和黏度随之增大;涂膜的接触角和断裂伸长率随DMPA含量的增加而减小,拉伸强度随DMPA含量的增加而增加;软段微区的结晶性能随着DMPA含量的增加而减小,当DMPA质量分数增加至5.6%时,软段微区表现出非晶态。     

Microstructural,thermal and rheological correlations to mechanical response of polyamide-6(glass filled)/polyetherimide blend: effect of ethylene-octene copolymer on toughening of blend

Melt mixed glass-filled polyamide 6(PA6)/polyetherimide (PEI) blends were prepared in a co-rotating twin screw extruder over the entire composition range of 0–100 wt% of polyamide 6. These blends were characterized by structural, rheological, mechanical and thermal properties. Crystallization behavior and phase morphology of the blends were also investigated. The blend with the composition PA6/PEI 75/25 showed overall improved mechanical properties along with low resultant viscosity which can be processed on standard equipment. Shear viscosity along with shear stress of the blends were analyzed using shear rheometer which concluded that the blends can be processed on standard equipment due to resultant low viscosity. Scanning electron microscope micrographs revealed that the morphology of the blends showed a two phase structure in which the minor phase was dispersed as domains in the continuous phase. Polyolefin elastomer (POE) as impact modifier was added to the above composition in the range of 0–15 phr to study its effect. The thermal characteristics of PA6, PEI, and PA6/PEI blends with and without POE were investigated using DSC and TGA which revealed that the melting temperature and crystallization temperature of the blend remained unchanged while XRD results showed percent crystallinity was increased slightly. Furthermore, it can be said that the blend with composition PA6/PEI 75/25 with 10 phr impact modifier loading was suitable for high end applications because it combines the high mechanical properties of glass-filled PA6 with inherent flame-retardant property of PEI while POE overcomes the physical weakness of moisture absorption.     

交联改性阴离子聚氨酯水分散体的制备与性能研究

由甲苯二异氰酸酯（TDI）、聚己内酯二醇（PCL）和二羟甲基丙酸（DMPA）反应,再与高醚化度甲醇醚化三聚氰胺甲醛树脂（HMMM）反应,制备了一种交联型阴离子水性聚氨酯。采用红外光谱对样品进行表征,并讨论了交联改性对聚氨酯乳液粒径分布、胶膜耐水性、力学性能、热稳定性及结晶度的影响。红外分析证实HMMM与聚氨酯发生了交联反应。当m（HMMM）∶m（—COOH）=2.25时,胶膜拉伸强度达到30.3MPa,吸水率为17.2%,吸乙醇率为10.9%,与水接触角为69.6°,Tmax（最快分解温度）为301.5℃,结晶度为1.10%。     

Novel mineralized heparin–gelatin nanoparticles for potential application in tissue engineering of bone

Nanoparticles (NPs) were prepared from succinylated gelatin (s-GL) cross-linked with aldehyde heparin (a-HEP) and used subsequently as a nano-template for the mineralization of hydroxyapatite (HAP). Gelatin was functionalized with succinyl groups that made it soluble at room temperature. Heparin was oxidized to generate aldehyde groups and then used as a cross-linker that can react with s-GL to form NPs via Schiff’s base linkage. The polymer concentrations, feed molar ratios and pH conditions were varied to fabricate NPs suspension. NPs were obtained with a spheroid shape of an average size of 196 nm at pH 2.5 and 202 nm at pH 7.4. These NPs had a positive zeta potential of 7.3 ± 3.0 mV and a narrow distribution with PDI 0.123 at pH 2.5, while they had a negative zeta potential of ?2.6 ± 0.3 mV and formed aggregates (PDI 0.257) at pH 7.4. The NPs prepared at pH 2.5 with a mean particle size of 196 nm were further used for mineralization studies. The mineralization process was mediated by solution without calcination at 37 °C. The HAP formed on NPs was analyzed by Fourier transform infrared spectroscopy and X-ray diffraction. HAP coated s-GL/a-HEP NPs developed in this study may be used in future as osteoinductive fillers enhancing the mechanical properties of injectable hydrogel or use as potential multifunctional device for nanotherapeutic approaches.     

Novel supramolecular hydrogels made via Michael-type addition reaction of dithiothreitol with self-assembly of α-cyclodextrins and acryloyl-terminated 3-arm PEG

A kind of novel three-dimensional crosslinked hydrogel was synthesized via Michael-type addition reaction of dithiothreitol (DTT) as a crosslinker/extender towards the self-assembly of α-cyclodextrins (α-CDs) with acryloyl end capped 3-arm PEG. The supramolecular structure of the resulting hydrogels was characterized by using FT-IR, TGA, XRD and DSC measurements. The effect of varying the amount of α-CDs was studied on the crosslinking process. Interestingly, this conjugation reaction is smoothly carried out at physiological temperature and pH in the absence of any sensitizer or catalyst. It appears that these chemically crosslinked hydrogels have the potential to be used as carriers for drug controlled release and scaffolds for injectable tissue engineering.     

Design and preparation of high-performance amine-based poly(ether ketone)s with strong photonic luminescence

Amine-based poly(ether ketone)s (A-PEKs), as novel high-performance functional polymers, have been obtained by the polycondensation of dibromo ketones with aromatic ether diamines via palladium-catalyzed aryl amination reaction. The structures of the polymers are characterized by means of FT-IR, ¹H NMR spectroscopy and elemental analysis, the results show a good agreement with the proposed structures. DSC and TGA measurements exhibit that polymers possess high glass transition temperature (T _g ≥ 175 °C) and good thermal stability with high decomposition temperatures (T ₅ ≥ 400 °C). Based on the hydrogen bonds between the polymer chains, thin films of A-PEKs show great mechanical behaviors with high tensile strength up to 89.5 Mpa. In addition, due to the photoinduced intramolecular charge-transfer (ICT) of A-PEKs, these synthesized polymers are endowed with significantly strong photonic luminescence in N,N′-dimethylformamide.     

Effect of calcining temperature on particle size of hydroxyapatite synthesized by solid-state reaction at room temperature

Using diammonium phosphate, calcium nitrate tetrahydrate and sodium bicarbonate as raw materials, hydroxyapatite (HAP) was facilely synthesized by solid-state reaction at room temperature. The crystallinity, phase, morphology and particle size of the products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry/differential thermal analysis (TG–DTA) and particle size analyzer. The influence of calcining temperature on the crystallinity and composition of HAP phase was also investigated.     

Thermal stability and electrical characteristics of poly(2-ethyleaniline)-Au nanocomposite

The Present work reports the synthesis of poly2-ethyleaniline (PEANI) by oxidative polymerization of 2-ethyleaniline and its composite with gold nanoparticles (AuNPs) via in situ chemical synthesis route (simultaneous polymerization and precipitation). PEANI and its nanocomposite were characterized by thermogravimetric analysis-differential Scanning Calorimetry, X-ray diffraction and Fourier transform-infrared. The structural confirmation of the polymer was confirmed by FT-IR which shows strong absorption starting at ~1,600 cm^?1 and extended to near-IR, Attributed to the presence of free carrier in the polymer. XRD of Polymer shows large X-rays peaks indicating that the material is rather amorphous with a certain degree of crystallinity where as XRD of PEANI-Au nanocomposite confirms the incorporation of AuNPs in composite. The TEM image showed the formation of PEANI-AuNPs core shell nanostructure. From TGA–DSC studies it was confirmed that the decomposition of the polymer in the composite is lowered by 254 °C as compare to PEANI alone, resulting in weak structure. Whereas I–V characteristics’ shows that the composite has about 10 % lower conductance values than the polymer alone.     

Study on the compatibility and crystalline morphology of NBR/PEO binary blends

Compatibility property, as well as crystalline morphology, of NBR/PEO blends has been investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized optical microscopy (POM) thoroughly. There is no apparent shift of nitrile or ether groups in the FTIR spectra of NBR/PEO blends. Based on the calculations from glass transition temperature, the maximum volume fraction of PEO dissolved in NBR phase is about 6.41 % in blend with 5 wt% PEO content (PEO-5), indicating a weak intermolecular interaction in the NBR/PEO blends. From the characteristic absorption bands in the FTIR spectra, XRD and POM graphs, the crystallinity ratio of NBR/PEO blends decreases as the NBR content increases, which is further proved by DSC measurement that the crystallinity ratio and crystal melting temperature of pure PEO are 82.6 %, 69.9 °C, and that of PEO-5 are 16.9 %, 59.5 °C. This illuminates that the weak intermolecular interaction will affect the crystallinity ratio and crystal melting temperature of the NBR/PEO blends.     

Controlled-release formulation of perindopril erbumine loaded PEG-coated magnetite nanoparticles for biomedical applications

Iron oxide nanoparticles (FNPs) were synthesized due to low toxicity and their ability to immobilize biological materials on their surfaces by the coprecipitation of iron salts in ammonia hydroxide followed by coating it with polyethylene glycol (PEG) to minimize the aggregation of iron oxide nanoparticles and enhance the effect of nanoparticles for biological applications. Then, the FNPs–PEG was loaded with perindopril erbumine (PE), an antihypertensive compound to form a new nanocomposite (FPEGPE). Transmission electron microscopy results showed that there are no significant differences between the sizes of FNPs and FPEGPE nanocomposite. The existence of PEG–PE was supported by the FTIR and TGA analyses. The PE loading (10.3 %) and the release profiles from FPEGPE nanocomposite were estimated using ultraviolet–visible spectroscopy which showed that up to 60.8 and 83.1 % of the adsorbed drug was released in 4223 and 1231 min at pH 7.4 and 4.8, respectively. However, the release of PE was completed very fast from a physical mixture (FNPs–PEG–PE) after 5 and 7 min at pH 4.8 and 7.4, respectively, which reveals that the release of PE from the physical mixture is not in the sustained-release manner. Cytotoxicity study showed that free PE presented slightly higher toxicity than the FNPs and FPEGPE nanocomposite. Therefore, the decrease toxicity against mouse normal fibroblast (3T3) cell lines prospective of this nanocomposite together with controlled-release behavior provided evidence of the possible beneficial biological activities of this new nanocomposite for nanopharmaceutical applications for both oral and non-oral routes.     

Enhanced hydrothermal stability of ZSM-5 formed from nanocrystalline seeds for naphtha catalytic cracking

We successfully synthesized hydrothermally stable ZSM-5 with crystalline nano seeds. We employed a template-free method using ZSM-5 crystalline nano seeds and sodium silicate as a silica source. The prepared ZSM-5 exhibited uniform crystal size and relative crystallinity greater than 100 %. The size of the crystalline nano seed in the scale of 100 nm was found to be the optimum size for obtaining uniform, highly crystalline ZSM-5 with structural stability. After P-modification, the synthesized ZSM-5 with the optimally sized seed showed high hydrothermal stability and improved catalytic naphtha cracking activity compared to a commercial ZSM-5 catalyst. In order to find the elements for the increased hydrothermal stability, the samples were evaluated by studying crystallinity, aluminum spectrum, and acidity using XRD, solid-state NMR, and NH₃-TPD, respectively after steaming at 800 °C for 24 h. It is speculated that the increased hydrothermal stability of the ZSM-5 resulted mainly from the increased aluminum structural stability.     

纳米TiC粉末在水中的分散性

通过沉降观察和粘度测定,探讨了pH值和分散剂聚乙烯亚氨（PEI）对纳米TiC粉末分散性的影响,借助FTIR和Zeta电位测定颗粒的表面成分和带电性质,结果表明,pH值和PEI浓度对粉末的分散性有极大影响,制得分散稳定的料浆的pH值和PEI添加量的最佳值分别为pH=11．40和0．0645wt％。     

Comparative investigation of Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) in the determination of cotton fiber crystallinity

Despite considerable efforts in developing curve-fitting protocols to evaluate the crystallinity index (CI) from X-ray diffraction (XRD) measurements, in its present state XRD can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline or amorphous fraction in a sample. The greatest barrier to establishing quantitative XRD is the lack of appropriate cellulose standards, which are needed to calibrate the XRD measurements. In practice, samples with known CI are very difficult to prepare or determine. In a previous study, we reported the development of a simple algorithm for determining fiber crystallinity information from Fourier transform infrared (FT-IR) spectroscopy. Hence, in this study we not only compared the fiber crystallinity information between FT-IR and XRD measurements, by developing a simple XRD algorithm in place of a time-consuming and subjective curve-fitting process, but we also suggested a direct way of determining cotton cellulose CI by calibrating XRD with the use of CI(IR) as references.     

Comparative performance of collagen nanofibers electrospun from different solvents and stabilized by different crosslinkers

Collagen electrospun scaffolds well reproduce the structure of the extracellular matrix (ECM) of natural tissues by coupling high biomimetism of the biological material with the fibrous morphology of the protein. Structural properties of collagen electrospun fibers are still a debated subject and there are conflicting reports in the literature addressing the presence of ultrastructure of collagen in electrospun fibers. In this work collagen type I was successfully electrospun from two different solvents, trifluoroethanol (TFE) and dilute acetic acid (AcOH). Characterization of collagen fibers was performed by means of SEM, ATR-IR, Circular Dichroism and WAXD. We demonstrated that collagen fibers contained a very low amount of triple helix with respect to pristine collagen (18 and 16 % in fibers electrospun from AcOH and TFE, respectively) and that triple helix denaturation occurred during polymer dissolution. Collagen scaffolds were crosslinked by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), a commonly employed crosslinker for electrospun collagen, and 1,4-butanediol diglycidyl ether (BDDGE), that was tested for the first time in this work as crosslinking agent for collagen in the form of electrospun fibers. We demonstrated that BDDGE successfully crosslinked collagen and preserved at the same time the scaffold fibrous morphology, while scaffolds crosslinked with EDC completely lost their porous structure. Mesenchymal stem cell experiments demonstrated that collagen scaffolds crosslinked with BDDGE are biocompatible and support cell attachment.