Copolymer Research Articles

Folate-conjugated Micelles Based on Star-shaped PLGA-PEG-NH2 Copolymers as Novel Tumor-targeted Nanocarriers

Folate-conjugated Micelles Based on Star-shaped PLGA-PEG-NH2 Copolymers as Novel Tumor-targeted Nanocarriers

Solubilization of the photosensitizers TPCS(2a) and TPPS(2a) in aqueous media evaluated by time-resolved fluorescence analysis.

The pH-dependent aggregation of the novel photosensitizer TPCS(2a) is investigated at low concentration (c = 10(-6) M) in aqueous media by means of time-correlated single-photon counting, and compared to that of the chemically related photosensitizer TPPS(2a). The efficacy of selected solubilizers, i.e., various nonionic Pluronic block copolymers and the nonionic surfactant Tween 80, in inhibiting aggregation of the two photosensitizers is evaluated, which is important for the further formulation of TPCS(2a).

A Fibrillar Biodegradable Scaffold for Blood Vessels Tissue Engineering

In recent years there has been a growing interest for the development of tubular scaffolds employed to assist the replacement of small blood vessels. Materials designed for this purpose need to be biodegradable, have good mechanical properties and improve cell adhesion, proliferation and differentiation. To obtain biomaterials with these properties, electrospinning seems to be one of the most useful technique. Several biodegradable synthetic polymers or constituents of the extracellular matrix (ECM) have been electrospun showing optimal mechanical properties and biodegradability. However, such polymers are lacking in versatile chemical structure affordable to immobilize growth factors or chemokines. The glycosaminoglycan heparin is able to bind several growth factors like vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) and, when grafted onto the scaffold surface it is able to attract cells thus improving their proliferation and differentiation.Aim of this research was the production and the preliminary in vitro biological characterization of a new biodegradable material, obtained by electrospun a polyaminoacid-graft-polyester copolymer. The electrospun biomaterial has been successfully grafted with heparin exploiting the better chemical reactivity of the polyaminoacid portions of the graft copolymer. Then its morphology has been investigated by scanning electron microscopy (SEM) and the potential biodegradability of the material has been studied until 60 days. Preliminary biological data in vitro, on human endothelial cells, show a good compatibility of the scaffold obtained by electrospinning, with regard to cell adhesion and proliferation. Experiments are in progress to evaluate the effects of heparin on cell differentiation.

1-甲基-3-(2-甲基丙烯酰乙基)-咪唑氯离子液体/ 苯乙烯无规共聚物及其CdTe量子点复合物的合成

Side-chain imidazolium-functionalized random copolymer P (MMEIM⁺Cl¯-co-St) was synthesized by free-radical copolymerization of 1-methyl-3-(2-methacryloyloxy ethyl) imidazolium chloride (MMEIM⁺Cl-) and styrene (St) with azodiisobutyrounitrile (AIBN) as initiator. The structure of random copolymer was characterized by FTIR, 1H NMR and GPC analyses. By the electrostatic interaction between positively charged imidazolium-functionalized P (MMEIM⁺Cl¯-co-St) and the negatively charged aqueous CdTe quantum dots (QDs), fluorescent nanocrystal-polymer composites CdTe/ P (MMEIM⁺Cl¯-co-St) were prepared conveniently. UV-Vis absorption and photoluminescence (PL) spectra indicated the photochemical stability and strong fluorescent emission of CdTe/ P (MMEIM⁺Cl¯-co-St) composites. The transmission electron microscopy (TEM) photograph shows that the CdTe QDs in composites are monodisperse, uniform and no significant surface deterioration or aggregation of the QDs occurred during the composite synthesis.

Graft copolymerization of Gelatin-g-poly (Acrylic acid-co-Acrylamide) and calculation of grafting parameters

In this research, we synthesized a novel graft copolymer of gelatin-based via radical polymerization mixtures Acrylic acid (AcA) and Acrylamide (AAm) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator. Evidence of grafting was obtained by comparing FTIR and TGA analysis of CMC and the graft copolymer as well as solubility characteristics of the products. The effect of grafting variables, i.e. concentration of AAm, AcA, APS and Gelatin, and temperature was systematically optimized to achieve a highest percent grafting possible. The overall activation energy for the grafting was also estimated to be 23.30kJ/mole.

Synthesis and Study on Effect of Various Chemical Conditions on the Swelling Property of Collagen- g -poly(AA- co -IA) Superabsorbent Hydrogel

In this work, a novel family of salt-responsive polymeric hydrogel based on collagen was prepared via simultaneously graft copolymerization of acrylic monomers, acrylic acid (AA) and itaconic acid (IA) onto collagen backbones by a free radical polymerization technique using ammonium persulfate (APS) as initiator and methylene bisacrylamide (MBA) as a crosslinker. The effect of grafting variables, i.e. AA/IA weight ratio and concentration of MBA and APS, was systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The water absorbency increased with increasing the AA/IA amount in the monomer feed due to formation of polyelectrolyte and then become constant. The swelling of the hydrogel samples in town water and saline solution (0.15 mol/L LiCl,NaCl,KCl, CaCl 2 and AlCl 3 ) was examined. Results indicated that the swelling capacity decreased with an increase charge of cation. This behavior can be attributed to charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations.finally,a mechanism for hydrogel formation was proposed and the structure of the product was established using Fourier transform infrared (FTIR) and Scanning Electron Microscopy (SEM) spectroscopies. Also, thermogravimetric analysis showed the thermal stabilities of the hydrogels.

Rheology of titania pigment slurry

The influence of polymeric dispersants containing different functional groups on the suspension behaviour of titania pigment slurry was investigated. The dispersants chosen were polyacrylic acid and modified polyacrylamides including homo and copolymers modified with carboxylate and/or hydroxyl groups. The pigment slurry rheology was strongly affected by both pH and dispersant chemical groups. The inorganic coating layer on the titania surface is not smooth, but rough or porous. The surface roughness of the pigment can generate additional contribution to the affinity of the dispersants for adsorption.

Synthesis and Self-assembly of Poly(ethylene oxide)-b- poly(lactic acid)-b-poly(2-hydroxyethyl methacrylate) Amphiphilic Triblock Copolymer

具有生物相容性的两亲性嵌段共聚物在水中易形成胶束，在医学诊断、体内药物缓释及药物靶向输送方面具有广阔的应用前景．利用二嵌段聚合物聚乙二醇-聚乳酸（PEG-PLA）引发甲基丙烯酸羟乙酯的原子转移自由基聚合，制备了两亲性三嵌段聚合物聚乙二醇-聚乳酸-聚甲基丙烯酸羟乙酯（PEG—PLA－PHEMA），利用凝胶渗透色谱（GPC），红外光谱（FT-IR），1HNMR表征了其聚合物组成；然后利用透析法制备了不同分子量的聚合物胶束，动态光散射（DLS）和透射电镜（TEM）结果表明其形貌规整、尺寸均-，而且胶束粒径在PEG和PLA链段长度不变的条件下，随PHEMA链段的变长而增大．PHEMA链上大量羟基的存在为聚合物胶束的功能化改性提供了反应位点，加上本身完全由具良好生物相容性的聚合物制备，使其在可控药物释放方面具有很大的应用潜力．

Polystyrene-co-poly(2,3,4,5,6-pentafluoro styrene) Copolymers: Synthesis and Fabrication of Their Porous Films

利用原子转移自由基聚合（ATRP）方法，分别在三氟甲苯、含氟离子液体以及三氟甲苯／含氟离子液体混合溶剂体系中合成了聚苯乙烯-co-聚（2，3，4，5，6．五氟苯乙烯）（PS．co．PPFS）共聚物，通过1HNMR、19F NMR、元素分析以及凝胶渗透色谱法（GPC）对所得聚合物的分子链结构和组成进行了分析和表征．随后，利用静态呼吸图法分别在CS2，CHCl3和CH2Cl2中制备了有序多孔薄膜，用扫描电子显微镜（SEM）观察其表面形貌，并与利用分子量大小相当的聚苯乙烯均聚物（PS）制备的多孑L薄膜进行了对比．研究结果表明：在三氟甲苯和含氟离子液体溶剂体系中，均可利用ATRP聚合方法获得窄分子量分布的PS．co—PPFS共聚物（Mn=5200-7900g·mol^-1，Mw／Mn=1．12～1．22）．对聚合物薄膜的扫描电子显微镜（SEM）观察和分析显示：分别以CS2，CHCl3和CH2Cl2作为溶剂，利用静态呼吸图法均可制备出PS—co．PPFS共聚物多孔薄膜．然而，与在CHCl3和CH2Cl2中制备的PS均聚物多孔薄膜的表面形貌不同的是，PS—co．PPFS共聚物多孔薄膜呈现出无序排列、平均孔径大小不同的两种孔结构；在CHCl3中制备所得薄膜的孔结构有序性相对较好，两种孔的平均孔径分别为0．75和0．37μm．

Modeling of Early Stages of Formation of Poly-CO

ABSTRACTWe studied the early stages of polymerization of CO under pressure. We performed DFT simulations of 128 and 432 atom models. Structures of random networks found at zero temperature were used for equilibration at 100 K by employing first principles MD. We found that the polymerization begins at 7 - 8 GPa and slightly depends on the size of the model. It turned out that there are several metastable phases of the extended CO solid, corresponding to different compression pressures from 7 - 8 GPa to 15-18 GPa with different numbers of CO fragments, not connected to the random network. We also found that the transition to the phases is irreversible which results in hysteresis loops. Random network structures obtained, say, under 18 GPa could exist at 3 GPa, whereas compression to 3 GPa results in the delta phase of CO crystal, with intact CO fragments and minor distortion of the cubic phase. To analyze the random structure fragments we calculated normal modes and IR intensities using the dipole approximation. Contributions from the main motifs of the random network are identified and compared with experimental IR measurements.

Control of Arrangement for DNA Molecules Chemisorbed to the Organized Molecular Films of Comb Copolymers Containing <i>s</i>-Triazine

Adsorption behavior of DNA molecules to comb copoly mers containing 2-vinyl-4, 6-diamino-1, 3, 5-triazine (VDAT) at air/water interface and their molecular arrangement have investigated by surface pressure-area (π-A) isotherm, IR spectroscopy, pola rized UV-vis spectroscopy, and atomic force microscopy. A newly hydrogenated and fluorinated b inary comb copolymers containing VDAT as adsorption template was synthesized by radical copo lymerization. From the result of π-A isotherm of monolayer on DNA aqueous solution, an increase of v alue for molecular area per VDAT unit corresponds to 20 A 2 . The IR spectrum of transferred LB multilayer ind icates adsorption of DNA molecules by hydrogen bonding to the copolymer templates. AFM images sho w the circular domain at 50-60 nm diameters. Adsorbed DNA molecules showed the absorption band a t 260 nm and emitted fluorescence at 400 nm. From the results of polarized UV-vis spectroscopy, these absorption bands indicate faint polarized dependency. In addition, emission bands in fluores cence spectrum of adsorbed DNA to copolymer film showed red-shift and became sharper than the one of their solution.

Transarterial embolization of traumatic carotid cavernous fistulas with ethylene vinyl alcohol copolymer ( Onyx)

Objective To summarize the preliminary experience and effectiveness of treatment for traumatic carotid cavernous fistulas with ethylene vinyl alcohol copolymer(Onyx).Methods In 6 cases of 7traumatic carotid cavernous fistula,we covered the fistulas with balloons,and selected the cavernous sinus through the fistula,then embolized the fistulas with pure Onyx or combination of coils or detachable balloons.Results One cases with bilateral TCCFs received secondary treatment considering the great change of cerebral blood flow after primary treatment of one - side fistula.Angiographic control revealed to 6 fistulas obliteration after primary treatment and all the cases had good patency of the internal carotid arteries.Clinical examination showed varying resolution of signs and symptoms of carotid cavernous fistulas,and the postoperative visual acuity of 4 patients were recovered totally.There was no recurrent fistulas in 2 -7months follow - up by DSA or MRA in 3 cases.Conclusions Transarterial embolization of complicated traumatic carotid cavernous fistulas with Onyx,assisted by balloons,proves to be more effective and safer than that with detachable balloons. Key words: Traumatic carotid cavernous fistulas; Embolization; Onyx

Succinylated Pullulan Acetate Microspheres for Protein Delivery

【In order to develop new protein carrier replacing poly(DL-lactic acid-co-glycolic acid) (PLGA) microspheres, succinylated pullulan acetate (SPA) was investigated to fabricate a long term protein delivery carrier. SPA microspheres loaded with lysozyme (Lys) as a model protein drug were prepared by a water/oil/water (W/O/W) double emulsion method. An acidity test of SPA copolymers after hydrolysis was performed to estimate the change of protein stability during releasing proteins from the microspheres. There was no pH change of SPA copolymers, but pH of PLGA polymers after hydrolysis was significantly decreased to around pH 2, indicating that the long-term stability of proteins released from SPA microspheres can be guaranteed. Loading efficiency of proteins into SPA microspheres was three times higher than those into conventional PLGA microspheres, indication of inducing stronger charge interaction between proteins and succinyl groups in SPA microspheres. Although initial burst behaviors were monitored in Lys-loaded SPA microspheres due to relatively strong hydrophilic succinyl segments in SPA microspheres, initial burst issues would be circumvented if the ratio of charge density of succinyl moieties and hydrophobic acetate groups is harmonically controlled. Therefore, in this study, a new attempt of protein delivery system was made and functional SPA was successfully confirmed as a new protein carrier.】

Synthesis and Characterization of Core-shell Acrylic/polyurethane Emulsion with Unsaturated Macromolecule Monomer Method

Acrylic/polyurethane(PUA) hybrid emulsion has been prepared by water-borne polyurethane(WPU) modified with acrylic resin.A method for adding different mass fraction of acrylic(AC) into polyurethane(PU) polymers is proposed and verified through designed experiments.With increasing the polyacrylate(PA) mass fraction in the copolymer,the appearance of the emulsion changes from transparent to opacity,in the meantime,the particle size is increased.The TEM result reveals that PUA latex particles present clear core-shell structure and regular shape,and the size distribution is within the range of 60~120 nm.The results of FTIR indicate that the hydrogen bonding effect of PU hard segment first increased and then decreased,while the ordering of hard segment decreased with increasing the AC mass fraction.Compatibility and degree of mixing were developed under 75%AC added in copolymers.With increasing PA mass fraction,one glass transition temperature existed in the copolymers before the content of AC arrived 75%.Thermogravimetric analysis(TGA) shows that the temperatures for the maximal thermal mass-loss rate rose from 363 ℃ to 412 ℃,and water absorption for samples decreased from 11.3% to 5.7% with the increase of AC fraction.Additionally,the elasticity modulus of PUA was raised from 16.4 to 47.6 MPa,while the tensile strength was increased from 9.0 to 23.7 MPa,and the elongation at break changed from 365% to 408%.Furthermore,the composite latex viscosity is decresed,and the drying time is shortened,while glue film adhesion force becomes better.

Preparation and ultrasonic imaging of PFOB-Ioaded polymeric nanomicelle and nanovesicle

Objective To formed ranoscale ultrasound contrast agents loading PFOB by selfassembly of amphiphilic block copolymer for ultrasonic imaging in vivo and in vitro.Methods The biodegradable copolymer-poly(ethylene glycol)-b-poly (D, L-lactic acid) (PEG-PDLLA) self-assembled to form PFOB-loaded nanomicelle and nanovesicle with different PFOB concentration by solvent volatilization.The configuration and particle-sizing of resulting nanoparticles was determined,and their ultrasonic imaging in vitro and contrast-enhanced ultrasonography on subcutaneous tissue by focal injection in vivo were observed.Results In transmission electron microscope images, these micelles and vesicles appeared uniformly spherical with smooth surface.All the size distributions were narrow and mean diameters were from 404.3 to 475.8 nm using laser particle-sizing analyzer.In vitro and in vivo experiment showed that,the higher PFOB concentration, the more remarkable effect of ultrasound imaging.Especially, nanovesilces'ultrasonography effect was much better than nanomicelles' under same conditions.Conclusions PFOB-loaded nano-micelles and nano-vesicles prepared by solvent volatilization and self-assembly of PEG-PDLLA can obviously enhance ultrasound contrast and nanovesicle behaves better than nano-micelle. Key words: Ultrasonography; Microbubbles ; Nanotechnology

Synthesis of Starch-g-poly (acrylic Acid-co-2-hydroxy Ethyl Methacrylate) as Potential pH-sensitive Hydrogel-based Drug Delivery System

The present work focused on the design of drug delivery system (DDS) based on a pH-sensitive hydrogel. The hydrogels were prepared via graft copolymerization of mixtures of acrylic acid (AA) and 2-hydroxy ethyl methacrylate (HEMA) onto starch backbones by a free radical polymerization technique. Sodium bicarbonate (NaHCO3) was added to function as a foaming agent under acidic conditions, rendering the hydrogels to be porous. Porous structure of hydrogel was essential in this system to yield a large surface area so that 5-fluorouracil (5-FU) release could be facilitated. The hydrogel thus prepared possessed a porous structure as determined by scanning electron microscopy. Due to the reversible swelling behavior of the hydrogels, the synthesized networks can sense the environmental pH change and achieve an oscillatory release pattern. Using drug 5-FU as a model molecule, the in vitro controlled drugrelease behaviors of these hydrogels were investigated. The results indicate that the main parameter affecting the drug-release behavior of hydrogels is the pH of the solution. The release rate of 5-FU from hydrogel at pH 7.4 was faster than that at pH 1.2 due to the shrinkage of the hydrogel at pH 1.2.These results suggest that a porous hydrogel could potentially be a useful local delivery system to release drugs primarily at a specific site of body.

9-Alkylidene-9H-Fluorene-Containing Polymer for High-Efficiency Polymer Solar Cells

A novel donor-acceptor copolymer containing 9-alkylidene-9H-fluorene unit in the main chain, poly[9-(1-hexylheptylidene)-2,7-fluorene-alt-5, 5-(4,7-di-2-thienyl-5,6-dialkoxy-2,1,3-benzothiadiazole) ...

PECVD coatings for functionalization of point-of-care biosensor surfaces

In early stage disease diagnosis, an accurate and reliable measurement of low concentrations of specific biomarkers is a key need. The detection technique requires the reaction of an antibody, which is generally covalently bound to the biosensor platform, with its antigen. The application of Zeonor ®, a cyclo olefin copolymer (COP) with very low autofluorescence, good optical properties and high precision molding characteristics, as a biosensor platform has been demonstrated recently. Highly reproducible, industrial scale surface chemical modification of the COP plastic for covalent attachment of the biomolecules for specific recognition of the target, together with low non-specific binding of other proteins that may be present in the sample is a key challenge. In this work, the applicability of plasma enhanced chemical vapor deposition (PECVD) process has been demonstrated by depositing varying surface functionalities including amines, carboxylic, mercapto, epoxy and polyethylene glycol functionalities. The plasma functionalized coatings thus created possess both reactive and repellent sites on the biosensor chip, allowing the chip to be configured either for fluorescence or light scattering–based detection or for label-free surface plasmon resonance detection techniques. The versatility of the gas phase deposition process for building sequential chemistries on low cost and disposable plastic chips is presented in detail.

Radical polymerization of CO2 -induced emulsions: A novel route to polymeric nanoparticles

We report a novel type of heterogeneous polymerization that relies on CO2-assisted particle formation exploiting the homogeneous expansion limit. This approach enables complete decoupling of the particle formation process and the polymerization, thus potentially enabling superior control over particle size. It is shown that this technique gives access to markedly smaller polymeric nanoparticles of diameters less than 20 nm. The present approach, along with the benefits of using a benign medium, is also anticipated to be applicable to controlled/living radical polymerization techniques, which are difficult to implement as traditional dispersion polymerizations.

Preparation of a novel porous scaffold from poly(lacticco-glycolic acid)/hydroxyapatite

Background: Scaffolds for bone tissue engineering must meet functional requirements, porosity, biocompatibility, and biodegradability. Different polymeric scaffolds have been designed to satisfy these properties. Composite materials could improve mechanical properties compared with polymers, and structural integrity and flexibility compared with brittle ceramics. Objective: Fabricate poly (lactic-co-glycolic acid) (PLGA) /hydroxyapatite (HA) porous scaffolds by freezeextraction method, and evaluate the possibility for optimizing their biocompatibility by changing their HA content. Methods: Porous PLGA/HA composites structure were prepared by freezing a polymer solution, and then the solvent was extracted by a non-solvent and subsequently air-dried. The scaffolds were coated with triblock copolymer and sterilized by ultraviolet light. Human mesenchymal stem cells were cultured on the prepared scaffolds and were studied after three days by 4, 6-diamidino-2-phenylindole (DAPI) fluorescence microscopy. Results: Microstructural studies with SEM showed the formation of about 50 micrometer size porous structure and interconnected porosity so that cells were adhered well into the structure of the coated samples. DAPI fluorescence microscopy showed more cell adhesion to the coated scaffolds and cell diffusion into the pores are visible. Direct assay of cell proliferation performed with MTT test showed cell growing on the scaffold similar to or more than on control samples. Conclusion: The triblock-coated PLGA/HA porous scaffolds may provide cell adhesion and proliferation, demonstrating their potential application in bone engineering. Keywords: Cell adhesion, composite, freeze-extraction, human mesenchymal stem cells (hMSC), porous scaffold, tissue engineering