Preparation and structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanocomposite upon intercalating reaction

Poly(ethylene glycol) possessing pentaethylenehexamine at one end (N6-PEG) was prepared via a reductive amination reaction of aldehyde-ended PEG with pentaethylenehexamine. Using N6-PEG, an antibody/PEG co-immobilized surface was constructed on magnetic particles via an active ester reaction method. After immobilization of the antibody on the active ester surface, N6-PEG was reacted on the magnetic beads. A sandwich enzyme-linked immunosorbent assay (ELISA) system was newly constructed using PEG/antibody co-immobilized magnetic beads combined with an alkaline phosphatase (ALP)-assisted fluorescent detection system using alpha-fetoprotein (AFP) as a model antigen. The co-immobilization of both antibody and PEG on the magnetic bead surfaces reduced the nonspecific adsorption of proteins from cell lysates. Especially, when the magnetic particle surface was modified by N6-PEG mixtures with different molecular weights of 6000 and 2500 (6 kDa:2.5 kDa=9:1 w/w), the nonspecific adsorption of proteins was strongly suppressed. It is rather surprising for us that the sensitivity of the antibody on the surface was enhanced significantly when the PEG tethered chain was constructed in between the surface antibodies. Consequently, the mixed N6-PEG treatment showed a much higher S/N ratio than for the corresponding beads treated with bovine serum albumin (BSA), a conventional blocking reagent. Actually, when alpha-fetoprotein was analyzed by the magnetic bead-assisted ELISA thus constructed, the S/N ratio was about 20-fold higher for the mixed coating with PEG (6 kDa):PEG (2.5 kDa)=9:1, compared to the conventional BSA.     

聚乳酸/聚氧化乙烯共混体系的热行为和力学性能及流变行为

采用熔融共混方法制备了聚乳酸与聚氧化乙烯的共混物.细致研究了重均分子量分别为2 kDa、10kDa1、00 kDa和600 kDa的聚氧化乙烯对聚乳酸的改性效果,并使用DSC、DMA及旋转流变仪等分析了共混物的相容性、热行为、力学性能和流变行为.结果表明,在聚氧化乙烯的组分含量不超过20 wt%的前提下,共混体系保持为完全相容体系,当聚氧化乙烯的分子量超过10 kDa时,其对聚乳酸的增塑效果,不随分子量增加而降低;增加聚氧化乙烯的分子量,可以提高材料的弹性模量和熔体强度.     

PROPERTIES OF SILK FIBROIN/POLY(ETHYLENE GLYCOL)400 BLEND FILMS

The blend film of silk fibroin (SF) and poly(ethylene glycol)400 (PEG400) with a blend ratio of 2/1 (wt/wt) wasprepared simply by dropping a little PEG400 into the SF solution and then casting the mixed aqueous solution at 50℃. Theresulting film exhibited much better mechanical properties in the dry and wet state than SF itself, owing to theconformational change of SF in the blends from the random coil to the β-sheet structure and intermolecular hydrogen bondformation between SF and PEG400. Thermogravimetric analysis showed that the initial thermal decomposition temperatureof the blend film was 170℃, which was 80℃ lower than that of SF (250℃) and 20℃ higher than that of PEG400 (150℃),and indicated a Strong interaction between two components of the blend. No crystalline peaks were observed in the X-raydiffraction curve of the blend film. Cell culture test showed that SF/PEG400 was a suitable substrate for the growth of humanumbilical vein endothelial cells (HUVEC).     

Macromolecular crowding improves polymer encapsulation within giant lipid vesicles

We report the effect of macromolecular crowding on encapsulation efficiency of fluorescently labeled poly(ethylene glycol) (PEG) and dextran polymers within individual giant lipid vesicles (GVs). Low concentrations of the fluorescently labeled polymers (82 nM to 186 pM) were mixed with varying concentrations of nonfluorescent polymers that served as crowding agents during vesicle formation by gentle hydration. Encapsulation efficiency of the fluorescently labeled polymers in individual GVs (EEind) was determined via confocal fluorescence microscopy. EEind for high molecular weight polymers (e.g., fluorescein isothiocyanate (FITC)-dextran 500 and 2000 kDa) increased substantially in the presence of several weight percent unlabeled PEG or dextran. For example, when 0.24 microM FITC dextran 500 kDa was encapsulated, addition of 3% PEG 8 kDa improved the mean concentration in the GVs from 0.14 microM (+/-50%) to 0.24 microM (+/-12%). Light scattering data indicate reduced hydrodynamic radii for polymers as a function of increasing polymer concentration, suggesting that the improvements in EEind result from polymer condensation due to macromolecular crowding. Polymeric cosolutes did not significantly impact EEind for lower molecular weight polymers (e.g., Alexa Fluor 488-PEG 20 kDa), which already encapsulated efficiently (EEind to approximately 1). However, for both the higher and lower molecular weight labeled polymers, cosolutes led to improved uniformity in EEind for vesicles within a batch. Methods for improving the value and homogeneity of EEind for polymeric solutes in lipid vesicles are important in a variety of applications, including the use of vesicles as microreactors and as vehicles for drug delivery.     

Purification and modification by polyethylene glycol of a new human basic fibroblast growth factor mutant-hbFGF(Ser25,87,92)

The mutant of human basic fibroblast growth factor (hbFGF), hbFGF(Ser25,87,92), which was constructed by replacing the cysteine residues at the positions of the 25th, the 87th and the 92nd with serine residues, was coupled to polyethylene glycol (PEG) with a molecular size of 20 kDa (20K) (PEG(20K)) to obtain hbFGF derivative, PEG(20K)-hbFGF(Ser25,87,92). The optimal modified reaction was conducted at 12 degrees C for 12h with the molar ratio of PEG(20K) to hbFGF(Ser25,87,92) of 30:1. The result of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the modification rate was up to 60%. The PEGylated product retained binding affinity to heparin and could be purified by heparin affinity chromatography. Compared to hbFGF mutant, purified PEG(20K)-hbFGF(Ser25,87,92) retained about 34% of mitogenic activity. Heat-stability assay indicated that the modified product was more stable than the native protein at the temperature of 37 degrees C.     

Trapping of wide range mass-to-charge ions and dependence on matrix amount in internal source MALDI-FTMS

Internal ionization source MALDI-FTMS shows clear variation of number average molecular weight (M(n)) for an equimolar mixture of four PEG polymers (PEG 2000, PEG 4000, PEG 6000, PEG 8000) when the 2,5-dihydroxy benzoic acid (DHB) matrix to PEG ratio is varied or the laser power is changed. As the matrix to analyte ratio is increased, the analyte signal of higher molecular mass ions increases and the signal of lower mass ions decreases. Laser power dependence studies show a similar trend. Possible explanations for these observations are discussed.     

Looped structure of flowerlike micelles revealed by 1H NMR relaxometry and light scattering

We present experimental proof that so-called "flowerlike micelles" exist and that they have some distinctly different properties compared to their "starlike" counterparts. Amphiphilic AB diblock and BAB triblock copolymers consisting of poly(ethylene glycol) (PEG) as hydrophilic A block and thermosensitive poly(N-isopropylacrylamide) (pNIPAm) B block(s) were synthesized via atom transfer radical polymerization (ATRP). In aqueous solutions, both block copolymer types form micelles above the cloud point of pNIPAm. Static and dynamic light scattering measurements in combination with NMR relaxation experiments proved the existence of flowerlike micelles based on pNIPAm(16kDa)-PEG(4kDa)-pNIPAm(16kDa) which had a smaller radius and lower mass and aggregation number than starlike micelles based on mPEG(2kDa)-pNIPAm(16kDa). Furthermore, the PEG surface density was much lower for the flowerlike micelles, which we attribute to the looped configuration of the hydrophilic PEG block. (1)H NMR relaxation measurements showed biphasic T(2) relaxation for PEG, indicating rigid PEG segments close to the micelle core and more flexible distal segments. Even the flexible distal segments were shown to have a lower mobility in the flowerlike micelles compared to the starlike micelles, indicating strain due to loop formation. Taken together, it is demonstrated that self-assemblies of BAB triblock copolymers have their hydrophilic block in a looped conformation and thus indeed adopt a flowerlike conformation.     

Colloidal stability and drug incorporation aspects of micellar-like PLA–PEG nanoparticles

The drug delivery properties of a series of poly(lactic acid)–poly(ethylene glycol) (PLA–PEG) micellar-like nanoparticles have been assessed in terms of their colloidal stability and their ability to incorporate a water soluble drug. These studies have focused on a range of PLA–PEG copolymers with a fixed PEG block (5 kDa) and a varying PLA segment (3–110 kDa). In aqueous media, these copolymers formed micellar-like assemblies following precipitation from water miscible solvents. There was a controlled increase in the particle size as the molecular weight of the PLA block was increased. The characteristics of the PEG corona were also highly dependent on the PLA moiety. Copolymers with a low molecular weight PLA block (3–15 kDa) formed highly colloidally stable dispersions, with a complete PEG surface coverage. However, increasing the molecular weight of the PLA block resulted in significantly less colloidally stable nanoparticle dispersions, which flocculated in solvents that were significantly better than θ-solvents for the stabilising PEG chains. This can be attributed to a reduced PEG surface coverage and the probable presence of naked PLA ‘patches’ on the particle surface. These larger PLA–PEG nanoparticles (30:5–110:5) were found to be stabilised in the presence of serum components, which are thought to adsorb into the gaps on the particle surface and prevent flocculation. All of the dispersions were found to be stable under physiological conditions and therefore suitable for in vivo administration. A reasonable loading (3.1% w/w) of the micellar-like PLA–PEG 30:5 nanoparticles with the water soluble drug procaine hydrochloride was achieved. The incorporated drug was found to have no effect on the nanoparticle structure or recovery, which can be attributed to the micellar character of these assemblies and the presence of the stabilising PEG chains.     

Evaluation of the copper(II) complexing ability of ultrafiltered humic acid by the solvent extraction method.

A commercial humic acid dissolved in water was fractionated to nine samples by means of ultrafiltration (UF); the nominal molecular weight used for UF membranes was 1 k-200 kDa. Concerning the nine samples, copper(II) complexing capacities (CuCC) and conditional stability constants (beta) of the formed copper(II) complexes were measured by a solvent extraction method. A total organic carbon (TOC) and the UV-VIS absorption ratio (E350 nm/E450 nm) were also measured. From a comparison of these data, it was found that a) humic acids in each fraction formed two kinds of copper(II) complexes with different stability; b) the beta values obtained from each fraction were almost the same; c) large CuCC values were observed in the molecular weight range from 10 kDa to 20 kDa and below 1 kDa; d) molecules with molecular weight higher than 50 kDa scarcely had any copper(II) complexing ability; e) the values of CuCC/TOC of each fraction were in the range from 1.7 to 3.4 x 10(-7) mol mg(-1).     

不同分子量PEG的铜电镀液对电化学沉积铜行为的研究

研究了在酸性镀铜溶液中添加不同分子量的PEG对直径为50微米、深径比为1的镀层盲孔填充效果的影响.结果表明,随着PEG分子量的增加,电镀铜溶液的微孔填充力明显提高.电流密度为2 A/dm2,添加剂PEG分子量(u)超过6000时,镀液可以完全填充盲孔,镀层不出现任何空洞和缝隙.这是由于添加剂PEG能明显加强电镀铜镀液阴极极化,抑制了电镀铜的沉积.同时,PEG于镀液中的扩散系数还随其分子量的增加而降低,从而增加了SPS在微孔底部的吸附力,加速了电镀铜在微孔底部的沉积.进一步,增大PEG分子量,沉积铜膜的表面粗糙度、铜膜结晶度和电阻率均有所降低.     

凝胶色谱与多角激光光散射联用研究聚氧化乙烯的扩展效应和链构象

采用凝胶色谱与多角激光光散射联用的方法,测定了一系列不同分子量的聚乙二醇(PEG)和聚氧化乙烯(PEO)在色谱柱中的扩展效应.扩展因子随PEG/PEO分子量的增加而增大,经扩展效应改正后得到了样品的准确分子量和分子量分布.同时建立了PEO的Z均回转半径Rgz与重均分子量Mw之间的单分散标度关系:Rgz=0.0272 Mw0.56,结果表明,长链PEO在水溶液中由于排除体积效应采取溶胀的无规线团构象.     

Viscoelastic properties of heterogeneous network polymers from poly(D-glutamic acid) and poly(oxyethylene glycol)

A series of five heterogeneous network polymers was prepared from poly(D -glutamic acid) (PDG) and poly(oxyethylene glycol) (PEG), and their dynamic mechanical properties were studied. The content of PDG was fixed at 60% by weight, and the molecular weight of PEG was changed to obtain networks with various crosslink densities. An increase in the PEG molecular weight from 330 to 880 caused considerable broadening of tan δ and E″ curves, and peak temperatures for tan δ and E″ decreased slightly. Curves of tan δ and E″ for PDG–PEG 4000 (indicating a PEG component of molecular weight 4,000) were much broader and the existence of two peaks was recognized. These findings and x-ray photographs suggest that PDG–PEG 330, 570, and 880 give films of fairly uniform phase, but that PDG–PEG 1830 and 4000 give films with two-phase structure. The factors influencing the dynamic mechanical properties in decreasing order of effectiveness are found to be the proportions by weight of PDG and PEG, the compatibility of PDG with PEG, the crosslink density, and the concentration of free carboxyl groups. The infrared spectra of these polymers indicate that at least part of the PDG component retains the α-helix conformation.     

Identification and quantification of polyethylene glycol types in polyethylene glycol methyl ether and polyethylene glycol vinyl ether

Quantitative determination of polyethylene glycol (PEG) impurities in two monofunctional polyglycol types, PEG methyl ether (M-PEG) and PEG vinyl ether (V-PEG), has been carried out by reversed-phase liquid chromatography with evaporative light scattering detection (ELSD). In addition to optimizing the resolution between PEG and monofunctional PEG peaks, the major focus has been to determine the molecular weights of PEG impurities in M-PEG and V-PEG of diverse molecular weights. The latter is achieved by examining liquid chromatography–mass spectrometry (LC–MS) mass spectra of both monofunctional PEG and PEG in several cases, and matching peak retention times with those of available PEG standards for all M-PEG and V-PEG sample types. This information is helpful in selecting the appropriate PEG standard to determine PEG content in each sample type. ELSD response factors for various PEG standards have also been compared. It has been found that PEG standards with molecular weights from 1000 Da to 8000 Da show responses that are within 10% of each other. However, a low molecular weight PEG such as PEG 400, provides approximately 30% less response compared to its higher molecular weight counterparts.     

相同软硬段质量配比聚醚酯弹性体PEG/PBT的结构与表征

以熔融缩聚法合成了一系列聚乙二醇(PEG)/聚对苯二甲酸丁二醇酯(PBT)聚醚酯热塑性弹性体,用NMR,FTIR,DSC及力学性能测试等方法表征了材料的结构及性能.讨论了在相同软硬段质量配比下,不同软硬段长度对材料性能的影响.结果表明,随着软段PEG长度增加,硬段PBT长度相应增长,弹性模量基本保持不变,抗拉强度、屈服应力及特性粘度增加.     

The Synthesis of Poly(ethylene oxide)-Block-Polybutylacrylate

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Synthesis and Application of Low Molecular Weight PEI-Based Copolymers for siRNA Delivery with Smart Polymer Blends

Polyethylenimine (PEI) is a commonly used cationic polymer for small-interfering RNA (siRNA) delivery due to its high transfection efficiency at low commercial cost. However, high molecular weight PEI is cytotoxic and thus, its practical application is limited. In this study, different formulations of low molecular weight PEI (LMW-PEI) based copolymers polyethylenimine-g-polycaprolactone (PEI–PCL) (800 Da–40 kDa) and PEI–PCL–PEI (5–5–5 kDa) blended with or without polyethylene glycol-b-polycaprolactone (PEG–PCL) (5 kDa-4 kDa) are investigated to prepare nanoparticles via nanoprecipitation using a solvent displacement method with sizes ≈100 nm. PEG–PCL can stabilize the nanoparticles, improve their biocompatibility, and extend their circulation time in vivo. The nanoparticles composed of PEI–PCL–PEI and PEG–PCL show higher siRNA encapsulation efficiency than PEI–PCL/PEG–PCL based nanoparticles at low N/P ratios, higher cellular uptake, and a gene silencing efficiency of ≈40% as a result of the higher molecular weight PEI blocks. These results suggest that the PEI–PCL–PEI/PEG–PCL nanoparticle system could be a promising vehicle for siRNA delivery at minimal synthetic effort.     

Mechanical properties of solvolysis lignin-derived polyurethanes

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG-MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.     

Poly(acrylic acid)-poly(ethylene glycol) layers on positively charged surface coatings: molecular structure, protein resistance, and application to single protein deposition

A new copolymer (PAA-PEG2000) has been designed, consisting of a negatively charged poly(acrylic acid) (PAA) backbone to which poly(ethylene glycol) (PEG) side chains with a molecular weight of about 2 kDa were grafted in a molecular ratio of 3:10. It readily adsorbs to positively charged surfaces and may be considered to be the anionic counterpart of PEG-grafted poly(l-lysine) (PLL-PEG), which was first described by Kenausis et al. and is widely used to render negatively charged surfaces protein-resistant. The synthesis of PAA-PEG2000 can be carried out in aqueous solution at room temperature and does not require any sophisticated techniques such as handling in an inert gas atmosphere. Using ellipsometry and infrared reflection absorption spectroscopy (IRRAS), the film structure has been carefully analyzed for copolymer adsorption onto three different positively charged surfaces, namely, thin layers of poly(allylamine) (PAH), poly(ethyleneimine) (PEI) and (3-aminopropyl)triethoxysilane (APTES). Besides the film thickness, the conformation of the PEG chains and their orientation with respect to the surface normal appear to be important parameters for the protein resistance of the films. Although PAA-PEG2000 adsorbed to PAH and PEI renders the surfaces inert, only partial protein resistance has been observed if the copolymer is deposited on APTES. In a model application, we have generated heterogeneous surfaces composed of isolated small Au nanoparticles (AuNP's) embedded in a protein-resistant layer of PAA-PEG2000 and demonstrated that the AuNP's can serve as adsorption sites for single protein species. In the future, these nanopatterned surfaces may be used for the investigation of isolated proteins.     

Evaluation of the quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using an equimolar mixture of uniform poly(ethylene glycol) oligomers

Quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was elucidated using an equimolar mixture of uniform poly(ethylene glycol) (PEG) oligomers with no molecular weight distributions. Uniform PEG oligomers with degrees of polymerization n = 6-40 were separated from commercial PEG samples by preparative super-critical fluid chromatography. MALDI-TOF mass spectra of an equimolar mixture of the uniform PEG oligomers were recorded by adding a mixture of 2,5-dihydroxybenzoic acid as a matrix reagent and four chlorinated salts, i.e. LiCl, NaCl, KCl and RbCl. Remarkable non-quantitative effects were observed in the MALDI-TOF mass spectra in both the lower and higher molecular mass regions. At higher molecular masses greater than about 10(3), PEG oligomers with larger molecular mass yielded lower spectral intensities irrespective of the species of adduct cations and higher laser powers induced larger decreases in mass spectral intensities with the increase in their molecular masses. On the other hand, in the lower molecular mass region, less than about 10(3), the observed non-quantitative effect greatly depends on the species of adduct cations, indicating that the stability of the PEG-cation complex affects the MALDI-TOF mass spectral intensities of uniform PEG oligomers.     

臭氧降解法制备壳低聚糖及其结构表征

以85％脱乙酰度、相对分子质量为25×10^4的壳聚糖为原料,在20℃、pH为3、氧气流量0．7m^3／h的条件下降解6h,降解液用氨水调至pH为9,无沉淀,分别用截留相对分子质量为2k、3k、5k、10k的中空纤维膜超滤,获得所需聚合度的壳低聚糖。降解产物的结构用红外光谱、核磁共振碳谱表征,结果说明降解前后的结构基本没有变化。降解产物的聚合度用飞行时间质谱表征,其中经过2k中空纤维膜超滤后的壳低聚糖聚合度主要为4～10。