Influence of Mica Particles on the Rheological Properties and Thermal Stability of Poly（ lactic acid）

The influence of mica particles on the rheological and thermal properties of poly（ lactic acid）（ PLA） / mica composites were investigated by capillary rheometer and thermogravimetric（ TG）analysis. The results show that the PLA / mica blends are nonNewtonian pseudoplastic and display shear-thinning. The value of non-Newtonian index of the blends melt decreased obviously with the addition of mica particles but somehow even increased when shear rate exceeded 4 500 s- 1. In this work,it could be indicated that appropriate amount of mica particles could somehow enhance the resistance of PLA melt under high shear rate to deviate from Newtonian fluid. TG analysis shows that the thermal stability of PLA decreases a little after the incorporation of the mica particles.As mica particles decompose in a completely different way in contrast to PLA,this abnormal decrease of thermal stability of PLA / mica composite may be attributed to moisture stored between mica layers released at high temperature.     

pH-Compensation Effect of Lysine on the Acidic Degradation of Electrospun Poly（ lactide-co-glycolide） Fibers in PBS

Electrospun aligned ultrafine fibers of poly（ lactide-coglycolide）（ PLGA） can be used to construct biomimetic scaffolds for engineering those structurally anisotropic and dense tissues（ e. g.,tendon,ligament,etc.）. But the acidic degradation products of the PLGA could result in p H decrease in the vicinity of the scaffolds,which may give rise to biocompatibility concerns. To address the noted problem, this study was designed to evaluate the p Hcompensation capacity of using Lysine（ Lys） —a kind of basic amino acid on the acidic degradation products of PLGA. Ultrafine PLGA（ 50∶ 50） fibers with 0,10%,20%,and 30% by weight of Lys loadings were prepared by a stable jet electrospinning（ SJES）approach. The morphology,structure,and mechanical properties of the electrospun aligned fibrous mats of Lys-incorporated PLGA（ 50∶50） were characterized by scanning electron microscope（ SEM）,Fourier transform infrared spectroscopy（ FTIR）,and tensile testing,respectively. Thereafter,the fibrous PLGA（ 50 ∶50） scaffolds were subjected to degradation by being immersed in phosphate buffered saline（ PBS,p H 6. 86） solution at 37 ℃ for 5weeks. Our results show that the formed Lys / PLGA composite ultrafine fibers have a well-aligned and uniform morphology with a fineness of ca. 1 #m in diameter. Introduction of Lys led to increased mechanical performance; that is,when the Lys loading is less than 30%,tensile strength and Young＇s modulus of the aligned Lys / PLGA fibers reached up to the impressive values of 84. 5 MPa and 2. 4 GPa,respectively. Degradation results show that the p H of the PLGA group fell to 5. 6 in 5 weeks while the p H of the Lys /PLGA groups with 10%,20%, and 30% of Lys loadings was maintained at 6. 3, 6. 5 and 6. 7, respectively. This work demonstrated that incorporation of Lys into electrospun PLGA fibers could be an effective approach in mediating the p H decrease caused by the acidic degradation products of the PLGA.     

Synthesis of high molecular weight polylactic acid from aqueous lactic acid co-catalyzed by tin(II)chloride dihydrate and succinic anhydride

Poly(lactic acid) (PLA) is widely used as biodegradable plastic and biomedical materials due to its excellent me- chanical properties and biodegradable characterization. The price of poly(lactic acid) has gradually become com- petitive to the average alkene polymers since the method for the preparation of lactic acid from starch fermentation has been developed. With the decline of petroleum re- serves, much attention is devoted to polylactic acid due to its environmentally benignancy and its …     

Electro-spinning Antimicrobial N-halamine Modified Poly （vinyl alcohol） Nanofibers

Antimicrobial poly( vinyl alcohol)( PVA) nanofibrous composites were prepared by adding 3-( 2,3-dihydroxypropyl)-5,5-dimethylimidazolidine-2,4-dione( N-halamine diol) to the PVA solution using electro-spinning technique upon curing and exposure to diluted sodium hypochlorite. Scanning electron microscopy( SEM) demonstrates that PVA nanofibers formed with diameters of( 255 ±94) nm. Cross-linked PVA nanofibers with N-halamine diol precursor and 1,2,3,4-butanetetracarboxylic( BTCA) showed good water resistance. The chlorinated PVA nanofibrous mats completely inactivated Staphylococcus aureus( Gram-positive) and Escherichia coli O157: H7( Gram-negative) with 7 log reductions( the reduction of the bacterial concentration in logarithm) within 5min and 1 min of contact time,respectively.     

Structure Changes of Silk Fibroin（SF） by Blending with Poly（ε-caprolactone）（PCL）：Characterization of SF and PCL Blended Electrospinning Films

The mechanical properties and water solubility of electrospinning SF films limit their use as biomaterials. In order to develop a tissue engineering biomaterial with both satisfying biological properties and sufficient biomechanical properties,blended films composed of silk fibroin（ SF） and poly（ ε-caprolactone）（ PCL） were fabricated by electrospinning in this study. Scanning electron microscope（ SEM）, X-ray diffraction（ XRD）,thermal analysis,Fourier transform-infrared（ FT-IR）,Raman spectra,mechanical testing,and water solubility were used to characterize the morphological, structural and mechanical properties of the blended electrospinning films. Results showed that the diameter of the blended fiber was distributed between 600 and1000 nm,and the fiber diameter increased as the PCL content increased. There is no obvious phase separation due to the similarity and intermiscibility,as well as the interactions（ mainly hydrogen bonds）, between the two polymers. Meanwhile, the secondary structures of SF changed from random coils and Silk I to Silk II because of the interactions between SF and PCL. For this reason,the tensile strength and elongation at break of the electrospinning films improved significantly,and the water solubility decreased. In conclusion,the blended electrospinning films fabricated in this study showed satisfying mechanical properties and water insolubilities,and they may be promising biomaterials for applications in tissue engineering for blood vessels,nerve conduits,tendons,ligaments and other tissues.     

Preparation,Characterization, and Antitumor Efficacy of,Camptothecine-Loaded Hydroxyapatite / Poly （lactic-co,glycolic acid ） Composite Nanofibers via Electrospinning

In the past decade, various medicated nanofibrous scaffolds have been developed as effective drug delivery systems for postsurglcal cancer treatment. In this study, hydroxyapatite nanoparticles （HANPs） were used as carriers to load an anticancer （CPT）, and the CPT-Ioaded HANPs （CPT @HANPs） was then incorporated into poly（ lactic-co.glycolic acid） （PLGA） nanofibers via electrospinning. Thus fabricated medicated nanofibrous mats （ PLGA /CPT @ HANPs） were characterized by field emission scanning electron microscope （FESEM）, transmission electron microscope （TEM）, attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR） and X-ray diffraction （XRD）. The release prof＇des of CPT from the medicated electrospun mats were obtained and their in vitro anticancer efficacy against HeLa cells was also evaluated. The results showed that the CPT was successfully loaded onto the surface of HANPs, and the prepared electrospun mats exhibited a homogeneous and continuous morphology. Furthermore, the loaded CPT exhibited a sustained release behavior from the nanoflbrous mats and the released CPT showed a long-term anticancer efficacy against HeLa cells. Therefore, the prepared medicated electrospun mats may be served as an effective drug delivery device for local antitumor treatment.     

In vitro study of poly(ethylene carbonate) as a drug-eluting stent coating

An in vitro feasibility study of the use of poly(ethylene carbonate) (PEC) as a biodegradable coating material for drug-eluting stents is reported, and the performance of PEC is compared with that of poly(lactic-co-glycolic acid) (PLGA). Scanning electron microscopy (SEM) images of PEC and PLGA discs after treatment with an alkaline KO2 solution as a superoxide source showed that the PEC maintained its integrity whereas holes and small particles appeared during the treatment of PLGA. Sirolimus and paclitaxel were loaded into PEC and PLGA in order to study drug release performance. Attenuated total reflectance–infrared (ATR– FTIR) spectroscopy of sirolimus, PEC and the sirolimus-loaded PEC coating showed that no chemical reaction occurred between sirolimus and PEC. The results of atomic force microscopy (AFM) revealed that the mean roughness (Ra) values of the bare metal stent (BMS) and the drugeluting stent (DES) were 2.3 nm and 1.0 nm, respectively. After balloon expansion experiments, no delamination or destruction of the PEC coating was observed. The drug release profile of sirolimus was different from that of paclitaxel when PEC was employed as the drug carrier, and the release curves of sirolimus were different when PEC and PLGA were used as drug carriers. All the experimental results demonstrated that PEC was one of the best potential stent-coating materials.     

Preparation and mineralization of PLGA/Gt electrospun fiber mats

Poly(lactic-co-glycolic acid)(PLGA)/gelatin(Gt) ultrafine composite fibers were fabricated via electro-spinning.The effect of gelatin on the morphology and tensile property of the electrospun fiber mats was investigated.Mineralization was carried out in 10×simulated body fluid(10SBF).The deposited calcium phosphate(CaP) was identified by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR).Results indicated that the av...     

Study on Composite Poly(Ether Urethane) Solid Electrolytes

1 Results Poly(ether urethane) was composed of incompatible hardware and software.It had better mechanical properties at room temperature,good flexibility,and lower glass transition temperature[1].It was increased the transmission of charged ions that polyether soft segment occurred solvent role with the alkali metal salts[2].However,conductivity of room temperature was low,and the study was very few to inorganic oxide particles compositing poly(ether urethane).This indicates the importance of solid polymer electrolytes.In our laboratory,we have studied a solid polymer electrolytes (SPE) based on nano-SiO2 composite linear poly(ether urethane).     

Preparation, Characterization, and Comparison of Thermal Properties of Aromatic Polyether Imides

Two aromatic polyimides were prepared by two- step way. Firstly, the poly（amic acid）s were synthesized from 1, 3 - bis（4 - aminophenoxy）benzene and two different aromatic dianhydrides. Secondly, polyimides were prepared via thermal imidization of poly（amic acid） precursors. The polyimides prepared were insoluble in common organic solvents such as tetrahydrofuran, chloroform and N, N- dimethyiformamide. The inherent viscosities of poly（amic acid）s were 1.82 dL/g and 2.67 dL/g. The high inherent viscosities were due to the strong intra- or intermolecular hydrogen interaction. The polyimides were characterized by mechanical and thermal analysis. It was found that the samples are of excellent thermal stability, higher glass-transition temperature and excellent dynamic mechanical and thermal properties.     

Poly(dimethylsiloxane) based microchip for DNA electrophoresis

A novel poly(dimethylsiloxane)(PDMS) -based microchip for DNA separation through electrophoresis has been developed using a micro-electro-mechanical-system(MEMS) technology. Unlike previous hybrid PDMS microchip, one PDMS film is first created on glass support by pressing method in our microchip. Thus, increased band-broadening phenomena, arising from the material nonuniformity at the walls of microchannel, can be avoided in electrophoresis process. A low-viscosity hydroxypropylmethylcellulose-100 (HPMC-100) is used as the separation medium for fluorescent intercalator-labeled double-stranded DNA (dsDNA) fragments. Mannitol is introduced to PDMS-based microchip as a separation medium additive to enhance separation efficiency. At applied electric field strength of 150 V/cm, excellent separations of the PCR marker could be achieved with an effective separation distance of 25mm .     

STUDIES ON COPOLYCONDENSATION MECHANISMS FROM m-METHOXY-p-ACETOXYBENZOIC ACID,p-ACETOXYBENZOIC ACID AND POLY(ETHYLENE TEREPHTHALATE)

Copolycondensation mechanisms for the terpolyester system from m-methoxy-p-acetoxybenzoic acid,p-acetoxybenzoic acid and poly(ethylene terephthalate)are first investigatedby high resolution proton NMR spectroscopy at 400 MHz.A series of reactivity ratios of thecopolycondensation reactions are given.The results shown that the m-methoxy-p-acetoxybenzoicacid tends to homopolymerize,while the p-acetoxybenzoic acid,and the ethylene terephthalate unitespecially,tend to copolymerize with the m-methoxy-p-acetoxybenzoic acid.     

Production of Poly （3—Hydroxybutyrate—co—3—Hydroxyhexanoate） by Aeromonas hydrophila and Recombinant Escherichia coli

Aeromonas hydrophila (A. hydrophila) 4AK4 produced poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with an almost constant 3-hydroxyhexanoate (3HHx) content of 10 % - 15 % from lauric acid and/or soybean oil. Both A. hydrophila 4AK4 and recombinant Escherichia coil (E. coil) JMU193(pBH32) produced PHBHHx with controllable 3HHx content when fed lauric acid and another co-substrate. With glucose or gluconate as the co-substrate, the 3HHx content in the copolyester produced by A. hydrophila 4AK4 was reduced slightly from 12% to 9%. However, the 3HHx content in the copolyester produced by E. coll JMU193 (pBH32) was significantly reduced from 9% to 2% with fructose as the co-substrate. These results show that regulation of 3HHx content in PHBHHx can be achieved using genetically engineered E. coll.     

New Biodegradable Thermoplastic Multiblock Copolymers from Lactic Acid, ε-Caprolactone, Poly(Ethylene Oxide) and Toluene Diisocyanate

1 Introduction The interest in finding new biodegradable materials for applications in important areas has been motivated by environmental protection aspects. Foremost among the potentially biodegradable and biocompatible polymers, poly(lactic acid) and poly(ε-caprolactone) received considerable attention as their potential application in a wide range of biomedical and pharmaceutical areas was recognized.1IntroductionTheinterest infinding newbiodegradable materialsfor applicationsini mportant…     

From Polymeric Nanoparticles to Dye-containing Photonic Crystals:Synthesis,Self-assembling,Optical Features, Possible Applications

1 Results Self-assembling of monodisperse polymeric nanoparticles is a perspective method of obtaining photonic crystalline materials for optoelectronics,telecommunication industry and optosensorics.For tuning optical characteristics of photonic crystals it is advisable to functionalize nanoparticles by dyes absorbing or emitting light in the vicinity of the photonic band gap,which position depends on the nanoparticle diameter.To prepare monodisperse nanoparticles with the dye-functionalyzed surface emulsion copolymerization of styrene with functional comonomers methacrylic acid[1] or N-vinylformamide was investigated.Dyes were attached onto the surface of nanoparticles either by covalent binding with surface amino groups of poly(styrene-co-N-vinylformamide-co-4-aminostyrene) particles[2] or by the ionic interaction of cationic dyes (Rhodamine 6G,Acriflavine,and 1-(3-ammonium-propyl)-4-[(E)-2-(3,4-dimethoxyphenyl)-1-ethenyl]pyridinium perchlorate) with surface carboxylic groups of poly(styrene-co-methacrylic acid) particles.     

Design of Smart Polymer-Protein Conjugates and Smart Magnetic Nanoparticles for Use in Microfluidic Diagnostic Assays

1 Results In this talk,I will describe the design,synthesis and application of smart polymers for use in microfluidic diagnostic devices.We are synthesizing a variety of temperature- and pH-responsive polymers using RAFT living free radical polymerization techniques.This allows us to control molecular weight and to achieve a narrow MW distribution of the polymers. Furthermore,RAFT polymers have reactive end groups that are used to conjugate the polymers to proteins.We are also using those groups to bind and coat the smart polymers onto the surfaces of polymeric or magnetic nanoparticles.We have applied UV graft co-polymerization techniques to coat the channel surfaces in the microfluidic devices with the smart polymers.The smart polymers we work with include temperature-responsive polymers such as poly(N-isopropyl acrylamide) or PNIPAAm and pH-responsive polymers such as poly(propylacrylic acid) or PPAA.We are synthesizing random,block and graft copolymers of these compositions as well.     

Fabrication of PLGA coated silica nanorattle for controlling the drug release behavior

Silica nanorattle with hollow and mesoporous structure has been proven to be an excellent drug carrier.However,how to control the drug release from silica nanorattle is still a challenge.In this study,we designed two methods,in-situ polymerization method and water in oil in water(W/O/W) double emulsion method,to coat a nanosized poly(lactic-co-glycolic acid)(PLGA) layer onto the surface of silica nanorattle for controlling the drug release behavior.Hydrophobic antitumor drug docetaxel was loaded into the PLGA coated silica nanorattle(PLGA@SN).The drug release profile,cellular uptake and cytotoxicity on human liver cancer HepG2 cells were evaluated to prove that the PLGA layer plays an effective role in tuning the drug delivery.     

Electrospun Small Diameter Tubes to Mimic Mechanical Properties of Native Blood Vessels Using Poly (L-lactide-co-ε-caprolactone )and Silk Fibroin: a Preliminary Study

Mismatch in mechanical properties can induce intimal hyperplasia,which is one of the main reasons for the failure of small diameter artificial blood vessels. Electrospun small diameter tubes with tailored mechanical properties were fabricated through blending poly( L-lactide-co-ε-caprolactone)( PLCL) and silk fibroin( SF)with the mass ratios of 30 /70,50 /50,and 70 /30 in this study.Scanning electron microscopy( SEM) and mechanical testing were used to characterize morphological and mechanical properties of the tubes. Results showed that tensile strength of the tubes was higher than most of the native blood vessels,and elongations at break of them were improved greatly by blending PLCL. Compliances of the tubes were all higher than 1% /13. 33 kPa( 1% /100 mmHg).Particularly,tubes with blending mass ratio of 50 /50 showed similar compliance with human native femoral arteries,which provided a promising biomaterial that could be applied on small diameter vascular applications.     

Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

The Gas Sensitivity of Polypyrrole Film Fabricated by in Situ Polymerization

1 Results Polypyrrole (PPy) is a typical conducting polymer with high conductivity and good stability,and has been widely used for detection of gases including ammonia and nitroxide[1].However the reversiblity and selectivity of the response to these gases are always not satisfying.In the paper,conductive PPy film was deposited on the interdigital electrode modified by one bilayer of poly(diallyldimethylammonium chloride) and poly(sodium styrenesulfonate),by in-situ polymerization with FeCl3 as oxidizing agent and p-toluene sulfonic acid (p-TSA) as the doping agent[2] to prepare a resistive-type gas sensor.Its gas sensitive properties to NH3 ranged from 5.5×10-5 to 3.3×10-3 was investigated at room temperature,and it was found that its sensitivity was greatly affected by the polymerization time,concentration of FeCl3,p-TSA and monomer.Prolonging the polymerization time or increasing the concentration of the oxidizing agent or doping agent resulted in a lower resistance and smaller sensitivity of the PPy film.