Different Molecular Weights Of PEG Research Articles

Analysis of Poly(ethylene glycol) from the conservation of 17th century shipwreck Vasa and associated wooden objects

Analysis of Poly(ethylene glycol) from the conservation of 17th century shipwreck Vasa and associated wooden objects

Preparation and Properties of Shape Memory PEG/IEM Resin and Its Composite Designed for Ureter Stent.

In this paper, isocyanoethyl methacrylate (IEM) is used to functionalize the two ends of poly(ethylene glycol)(PEG) diol with acrylic acid groups through an urethanisation reaction. The synthesized PEG/IEM resin is then photo-cured with a 405nm ultraviolet lamp. Ttrans of the PEG/IEM resin can be regulated by the different molecular weights of PEG and the use of plasticizer Triacetin to reach 44°C, which is closer to the human body temperature. Cytotoxicity assay and DMA shape memory cycling testing show that the PEG/IEM resin has excellent biocompatibility and shape memory properties. The flower structure is prepared and its shape recovery process is demonstrated. The performance of 10wt% nano Fe3 O4 /PEG4000/IEM resin and its composite spring stent structure satisfy the requirement of the stent properties in vivo, and can quickly recover to the original shape under magneticallydriven. This work provides a material option for developing new biological application devices such as ureter stents. This article is protected by copyright. All rights reserved.

Synthesis of nanoparticles of Poly (ethyleneimine) and their characterization by transmission electron microscopy, thin layer chromatography, and infrared spectroscopy

Intracellular gene delivery alters the expression of a gene and corrects a defective gene that may be the cause of a disease or a disorder. Nonviral gene delivery is more appropriate than viral-mediated due to their low cytotoxicity and immunogenicity. Amongst these, polycationic nanoparticles i.e. Polyethyleneimine (PEI) were used most successfully. The PEGylation of such cationic polymer reduces its cytotoxicity. Different molecular weight poly (ethylene glycol) was used for the PEGylation of such cationic nanoparticles which have an individual effect. For this purpose, the PEG is esterified, which was then reacted with a cationic polymer. Four different molecular weights of PEG were used. The size of nanoparticles so formed depends upon the molecular weight of PEG. So formed nanoparticles were dialyzed, lyophilized, and then characterized by IR and TEM. The nanoparticles so formed are directly affected by the different molecular weights of PEG. Higher the molecular weights of PEG smaller size of nanoparticles so formed but only up to a limited extent. The decreasing order of nanoparticles as an increment of molecular weight of PEG was found as a -0.85 coefficient of correlation. The smaller-sized nanoparticles have higher transfection efficiency than larger-sized nanoparticles. So, the higher the molecular weight of PEG higher will be the transfection efficiency.

Self-Assembled Nanostructures from Amphiphilic Sucrose-Soyates for Solubilizing Hydrophobic Guest Molecules.

We studied self-assembly and colloidal properties of poly(ethylene glycol) (pEG) conjugated sucrose soyate polyols (PSSP). These molecular platforms were synthesized by covalently connecting PEGs of different molecular weights (Mn) (12 and 16 ethylene oxide units) to epoxidized sucrose soyate (ESS). The synthesized PSSP products showed amphiphilicity, reduced water surface tension, and exhibited critical Aggregation Concentration (CAC) within the range of 0.3-0.4 mg/mL. We observed that PSSP self-assembles in water in the form of nanoparticles without the need of any cosolvents. These nanoparticles exhibited number-average hydrodynamic diameter of 120 ± 8 nm with a polydispersity index (PDI) of <0.3, and negatively charged surfaces. We also found out that PSSP nanoparticles can encapsulate and homogeneously distribute a hydrophobic model compound, such as a phthalocyanine dye, Solvent Blue-70 (BL-70), on a metal surface. Collectively, our studies explored and demonstrated the possibility of molecular diversification of biobased starting materials to form amphiphilic nanoparticles with industrially relevant colloidal and surface properties.

Enhancement of intercellular interaction between iPSC-derived neural progenitor cells and activated endothelial cells using cell surface modification with functional oligopeptides.

Cell-based therapy has been used to treat stroke related disorders, which have no treatment options available 4.5 hours after onset. Although the administration of tissue plasminogen activator and mechanical thrombectomy are potent treatments, their clinical implementation is limited within the available time. Here, we aimed to use induced pluripotent stem cell-derived neural progenitor cells (NPCs) for stroke treatment with higher delivery efficiency in stroke areas, which will improve the therapeutic effect. E-selectin binding oligopeptide (Esbp) was conjugated with poly(ethylene glycol)-conjugated-lipid (Esbp-PEG-lipid) with different molecular weights of PEG (5 and 40 kDa) for cell surface modification. Then, we optimized the cell surface modification of NPCs by studying cell-binding ability onto the model surfaces of stroke areas, such as recombinant E-selectin-immobilized surfaces and TNF-α activated endothelium. As a result, the cell surface modification of NPCs with Esbp-PEG-lipid was found to induce specific intercellular interactions with the activated endothelium through the binding of Esbp with E-selectin. Additionally, the shorter PEG spacer was suitable for intercellular interactions. Thus, our technique shows potential for use in cell therapy with enhanced cell accumulation in infarct areas.

Synthesis of Hydrophilic Poly(butylene succinate-butylene dilinoleate) (PBS-DLS) Copolymers Containing Poly(Ethylene Glycol) (PEG) of Variable Molecular Weights.

Polymeric materials have numerous applications from the industrial to medical fields because of their vast controllable properties. In this study, we aimed to synthesize series of poly(butylene succinate-dilinoleic succinate-ethylene glycol succinate) (PBS-DLS-PEG) copolymers, by two-step polycondensation using a heterogeneous catalyst and a two-step process. PEG of different molecular weights, namely, 1000 g/mol and 6000 g/mol, was used in order to study its effect on the surface and thermal properties. The amount of the PBS hard segment in all copolymers was fixed at 70 wt%, while different ratios between the soft segments (DLS and PEG) were applied. The chemical structure of PBS-DLS-PEG was evaluated using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Gel permeation chromatography was used to determine the molecular weight and dispersity index. The results of structural analysis indicate the incorporation of PEG in the macrochain. The physical and thermal properties of the newly synthesized copolymers were also evaluated using water contact angle measurements, differential scanning calorimetry and dynamic thermomechanical analysis. It was found that increasing the amount of PEG of a higher molecular weight increased the surface wettability of the new materials while maintaining their thermal properties. Importantly, the two-step melt polycondensation allowed a direct fabrication of a polymeric filament with a well-controlled diameter directly from the reactor. The obtained results clearly show that the use of two-step polycondensation in the melt allows obtaining novel PBS-DLS-PEG copolymers and creates new opportunities for the controlled processing of these hydrophilic and thermally stable copolymers for 3D printing technology, which is increasingly used in medical techniques.

Induction of Spontaneous Liposome Adsorption by Exogenous Surface Modification with Cell-Penetrating Peptide-Conjugated Lipids.

The use of amphiphilic molecules such as poly(ethylene glycol)-conjugated phospholipid (PEG-lipid) enables incorporation into liposome surfaces by exogenous addition as a result of the self-assembly with lipids. This technique can be applicable for manipulation of both liposomes and cells. In this study, we aimed to characterize Tat peptide (YGRKKRRQRRR)-conjugated PEG-lipids when used to exogenously surface modify liposomes (size: ca. 100 nm). We earlier reported that cells, which were surface modified with Tat peptides conjugated to PEG-lipids could attach spontaneously to material surfaces without any chemical modification. Here, we synthesized different types of Tat-PEG-lipids by combining PEG of different molecular weights (5 and 40 kDa) with different lipids with three acyl chains (myristoyl, palmitoyl, and stearoyl, respectively) and then studied the spontaneous adsorption of modified liposomes onto a substrate surface induced by the different Tat-PEG-lipids. The amount of adsorbed liposomes strongly depended on the number of incorporated Tat-PEG-lipid moieties: a decrease in both the PEG and the acyl chain lengths led to adsorption of higher amounts of liposomes. Furthermore, when a collagenase-cleavable amino acid sequence was inserted between the Tat sequence and the PEG segment, adsorbed liposomes could be harvested from the substrate by collagenase treatment with no difference in desorption efficiency between the different Tat-PEG-lipids. Thus, Tat-PEG-lipid can be a suitable tool for the manipulation of liposomes and cells.

Design and Development of D‒α‒Tocopheryl Polyethylene Glycol Succinate‒block‒Poly(ε-Caprolactone) (TPGS-b-PCL) Nanocarriers for Solubilization and Controlled Release of Paclitaxel.

The objective of this study was to synthesize and characterize a set of biodegradable block copolymers based on TPGS-block-poly(ε-caprolactone) (TPGS-b-PCL) and to assess their self-assembled structures as a nanodelivery system for paclitaxel (PAX). The conjugation of PCL to TPGS was hypothesized to increase the stability and the drug solubilization characteristics of TPGS micelles. TPGS-b-PCL copolymer with various PCL/TPGS ratios were synthesized via ring opening bulk polymerization of ε-caprolactone using TPGS, with different molecular weights of PEG (1–5 kDa), as initiators and stannous octoate as a catalyst. The synthesized copolymers were characterized using 1H NMR, GPC, FTIR, XRD, and DSC. Assembly of block copolymers was achieved via the cosolvent evaporation method. The self-assembled structures were characterized for their size, polydispersity, and CMC using dynamic light scattering (DLS) technique. The results from the spectroscopic and thermal analyses confirmed the successful synthesis of the copolymers. Only copolymers that consisted of TPGS with PEG molecular weights ≥ 2000 Da were able to self-assemble and form nanocarriers of ≤200 nm in diameter. Moreover, TPGS2000-b-PCL4000, TPGS3500-b-PCL7000, and TPGS5000-b-PCL15000 micelles enhanced the aqueous solubility of PAX from 0.3 µg/mL up to 88.4 ug/mL in TPGS5000-b-PCL15000. Of the abovementioned micellar formulations, TPGS5000-b-PCL15000 showed the slowest in vitro release of PAX. Specifically, the PAX-loaded TPGS5000-b-PCL15000 micellar formulation showed less than 10% drug release within the first 12 h, and around 36% cumulative drug release within 72 h compared to 61% and 100% PAX release, respectively, from the commercially available formulation (Ebetaxel®) at the same time points. Our results point to a great potential for TPGS-b-PCL micelles to efficiently solubilize and control the release of PAX.

The Contribution of PEG Molecular Weights in PEGylated Emulsions to the Various Phases in the Accelerated Blood Clearance (ABC) Phenomenon in Rats.

PEGylated preparations will be cleared rapidly from blood circulation when they are administrated twice in the same animal at a time interval, referred to as the "accelerated blood clearance" (ABC) phenomenon. Commonly, the study of the ABC phenomenon was investigated in two aspects: induction phase and effectuation phase. Herein, we report the influence of physicochemical properties (PEG molecular weights) in the induction phase and effectuation phase on the ABC phenomenon. In the experiment, on one hand, PEGylated emulsions with different molecular weights of PEG (refer to PEn, n = 400, 600, 800, 1000, 2000, and 5000) were injected for the first dose (induction phase) and induced PE2000 to produce ABC phenomenon. On the other hand, after PE2000 injected, PEn was injected for the second dose (effectuation phase). The results indicated that PE2000 and PE5000 induced an intense ABC phenomenon by their long-circulating characteristic. Interestingly, PE400, PE600, PE800, and PE1000 produced a consistent ABC phenomenon but different circulation time. Apparently, the induction of the ABC phenomenon is not only determined by the circulation time but also by the PEG molecular weights. When PEn is in the effectuation phase, the extent of the ABC phenomenon was not positively related to the molecular weights of PEG, increasing first and then weaken with the increase of molecular weights of PEG. These suggest that the number of -(CH2CH2O)n- repeat units of PE2000 was more conducive to interact with anti-PEG IgM. The results reported here clearly indicate that both the PEG molecular weights of prior dose and the subsequent dose of emulsion strongly influence the extent of the ABC phenomenon. Taken together, our observations in this study complete the effect of PEG molecular weights at a different phase of the ABC phenomenon. Furthermore, our findings have a significant impact on the choice of molecular weights for PEGylated formulations for use in cross-administration.

Nucleic Acid Delivery with α-Tocopherol-Polyethyleneimine-Polyethylene Glycol Nanocarrier System.

PurposeNucleic acid-based therapies are a promising therapeutic tool. The major obstacle in their clinical translation is their efficient delivery to the desired tissue. We developed a novel nanosized delivery system composed of conjugates of α-tocopherol, polyethyleneimine, and polyethylene glycol (TPP) to deliver nucleic acids.MethodsWe synthesized a panel of TPP molecules using different molecular weights of PEG and PEI and analyzed with various analytical approaches. The optimized version of TPP (TPP111 - the 1:1:1 molecular ratio) was self-assembled in water to produce nanostructures and then evaluated in diversified in vitro and in vivo studies.ResultsThrough a panel of synthesized molecules, TPP111 conjugate components self-assembled in water, forming globular shaped nanostructures of ~90 nm, with high nucleic acid entrapment efficiency. The polymer had low cytotoxicity in vitro and protected nucleic acids from nucleases. Using a luciferase-expressing plasmid, TPP111-plasmid nano-complexes were rapidly up-taken by cancer cells in vitro and induced strong transfection, comparable to PEI. Colocalization of the nano-complexes and endosomes/lysosomes suggested an endosome-mediated uptake. Using a subcutaneous tumor model, intravenously injected nano-complexes preferentially accumulated to the tumor area over 24 h.ConclusionThese results indicate that we successfully synthesized the TPP111 nanocarrier system, which can deliver nucleic acids in vitro and in vivo and merits further evaluation.

A polyester with hyperbranched architecture as potential nano-grade antibiotics: An in-vitro study

A potential nanograde antibiotic with hyperbranched architecture was synthesized from melt esterification of poly(ethylene glycol) or PEG and Citric acid or CA with 1:1 mol composition. PEG of different molecular weights, c.a. 4000, 6000 and 20,000 were used during the polyesterification. The polyester molecules of nanometric size were highly water soluble and showed a melting point between 55 and 60 °C. The branching status was established from spectroscopy, flow behaviour (viscosity) and rheological evidences. The extent of branching and flowability, both were reduced as the molecular weight of PEG was increased. During in-vitro pathological study, all the grades showed reasonably strong antibacterial affect (both with gram positive and negative bacteria), high selectivity, biocompatibility and controlled generation of reactive oxygen species or ROS, however, the grade with maximum level of branching and functional chain ends displayed highest therapeutic efficiency, may that be considered further as a potential agent for next level investigation.

PEGylated BF2-Azadipyrromethene (NIR-AZA) fluorophores, for intraoperative imaging

Clinical imaging utilising near-infrared fluorescence is growing as an intraoperative aid for the decision-making processes during complex surgical procedures. Existing uses include perfusion assessment and lymph node identification with many new applications currently being proposed and developed. While imaging hardware and software have significantly progressed in recent times, suitable NIR-fluorophores remain a limiting factor. In this report, we describe the design, synthesis, photophysical characterization and invivo imaging assessment of new PEGylated NIR-fluorophores based on the BF2-azadipyrromethene fluorophore class. The synthetic route includes PEGylation as the final step, thereby allowing routine access to derivatives substituted with different molecular weights of PEG. Absorption and emission wavelength maxima in PBS lie at 690 and 720 nm respectively with quantum yields over 12%. They show excellent photostability and no light induced singlet oxygen production. A time-course of NIR-fluorescence imaging, post i.v. administration, in BALB/c mice showed a rapid and preferential accumulation in the renal excretion pathway within 20 min, indicative of potential clinical usage for intraoperative identification of vial structures along this pathway. Assessment with clinical imaging equipment showed the NIR-AZA fluorophores to be wavelength compatible and brighter than currently used methylene blue (MB), and that they have the ability to be imaged simultaneously with indocyanine green (ICG) offering a potential for dual colour clinical imaging.

Light-scattering data of protein and polymer solutions: A new approach for model validation and parameter estimation

The development of separation processes for polymers or proteins from aqueous solutions requires a high amount of experimental effort, including phase-equilibrium data such as solid-liquid, liquid-liquid or vapor-liquid equilibria. This effort can be reduced by means of thermodynamic models. This work presents a new method for parameter estimation and validation of thermodynamic models by means of static-light-scattering (SLS) measurements. In this work the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to predict directly the SLS data (Rayleigh ratio) of macromolecular solutions. In a first step, SLS data were measured for binary water/polyethylene glycol (PEG molecular weight ranging from 2000 to 12000 g/mol) mixtures and for binary water/lysozyme mixtures. Applying pure-component PC-SAFT parameters from literature, the SLS data of these binary mixtures were successfully predicted with PC-SAFT. In a second step, one binary interaction parameter between lysozyme and PEG was adjusted to new experimental SLS data of buffered PEG/lysozyme/water solutions with PEG6000 concentration of 20 g/L. Finally, SLS data for buffered ternary PEG/lysozyme/water solutions with PEG of different molecular weights (2000–12000 g/mol) and different concentrations (1–50 g/L) were accurately predicted with PC-SAFT. Thus, (1) the proposed approach allows predicting SLS data, and (2) the method provides an access to the estimation of model parameters by means of experimental SLS data, which are accessible with much less effort than experimental phase-equilibrium data.

Synergistic influence of inhibition of PEG-surfactant on the rate of alkaline hydrolysis of procaine

Abstract The effect of surfactants (sodium dodecyl sulphate; SDS, cetyltrimethyl ammonium bromide; CTABr, and Triton X-100; TX100) and polymeric surfactants (viz. polyethylene glycol; PEG) mixture on the rate of base catalyzed hydrolysis of procaine hydrochloride (2-diethylaminoethyl-4-aminobenzoic acid) has been studied under the pseudo-first-order conditions ([OH¯] ≫ [Procaine]). The rate of hydrolysis of procaine was found to be linearly dependent upon the [NaOH] in the range from 2.0 × 10−2 mol dm−3 to 8.0 × 10−1 mol dm−3 at fixed [procaine] (=5.0 × 10−5 mol dm−3) at 37 °C. The values of rate constant were found to be independent on [procaine] in the concentration range from 1.0 × 10−5 mol dm−3 to 1.0 × 10−4 mol dm−3 at a fixed concentration of NaOH at 5.0 × 10−2 mol dm−3. The values of rate constant decreased with the increase in the concentrations of surfactants (SDS, CTABr and TX100). The rate of hydrolysis further decreased with the addition of PEGs of different molecular weights (1500, 4000, 6000 and 8000) in the reaction media containing surfactant. The increase in the concentration of PEGs from 1% to 5% decreased the rate of hydrolysis, thereby, increasing its stability. The increase in molecular weight of PEG also decreased the rate of hydrolysis. The kinetic parameters and binding constants (e.g. km, Kp for the different reaction media) were calculated for the reactions occurring in the aqueous and surfactant-PEG pseudophases by applying pseudophase ion exchange model. Maximum inhibition in the rate of hydrolysis was observed for PEG-TX100 aggregates.

Starch-polyurethane films synthesized using polyethylene glycol-isocyanate (PEG-iso): Effects of molecular weight, crystallinity, and composition of PEG-iso on physiochemical characteristics and hydrophobicity of the films

Abstract Starch-polyurethane (PU) films were prepared using glycerol gelatinized high amylose starch (HAGS) and PEG-iso linkers. The PEG-iso linkers were synthesized by reacting PEGs of different molecular weights (600, 1000, 1500 and 2050 Da) with hexamethylene diisocyanate (HDI). PEG-iso linkers were chemically grafted into HAGS forming three dimensional urethane (PEG-PU) networks. The HAGS-PEG-PU films were prepared by using 2, 5, 10, 15 and 20% (w/w) of PEG-iso linkers on solid basis. The tensile strength, elongation and hydrophobicity (measured as contact angle) of HAGS-PEG-PU films were significantly affected by the chain lengths of the PEG-iso linkers and their concentration in the film. Intermolecular hydrogen bonding between HAGS and PEG-iso linkers increased with the increase of PEG-iso content in the films. At a fixed MW of PEG-iso linker, an increase of its concentration up to 20% (w/w) improved the compatibility and formation of interpenetrating networks between HAGS and PEG-PU. The highest flexibility (1166% elongation at break) in HAGS-PEG-PU films was obtained when PEG-iso linker synthesized with PEG 1000 Da was used. The ultimate tensile strength of the films increased when PEG-iso linkers with higher chain lengths were used. The hydrophobicity of the films was found to depend on the hydrogen bond density, degree of chain entanglement and crystalline structure and compatibility between HAGS and PEG-PU in the film matrix.

Poly(Ethylene Glycol) Dimethacrylates with Cleavable Ketal Sites: Precursors for Cleavable PEG‐Hydrogels

The authors introduce poly(ethylene glycol) (PEG) based macromonomers containing acid-labile ketal moieties as well as terminal methacrylate units that are amenable to radical polymerization. The synthesis of PEGs of different molecular weights (ranging from 2000 to 13 000 g mol-1 with polydispersities <1.15) with a central ketal unit (PEG-ketal-diol) and their conversion to PEG-ketal-dimethacrylates (PEG-ketal-DMA) is introduced. Degradation rates of both PEG-ketal-diols and PEG-ketal-DMA are investigated by in situ 1 H NMR kinetic studies in deuterated phosphate buffer. Hydrogels containing 0, 5, or 10 wt% of PEG-ketal-DMA and 100, 95, or 90 wt% of PEG-DMA, respectively, are synthesized and disintegration of the gels is investigated in buffer at different pH values. Visible disintegration of the gels appears at pH 5 for hydrogels containing PEG-ketal-DMA, whereas no visible degradation is observed at all at neutral pH or for PEG hydrogels without PEG-ketal-DMA.

Surface Distribution and Biophysicochemical Properties of Polymeric Micelles Bearing Gemini Cationic and Hydrophilic Groups.

Polymeric micelles containing cationic gemini quaternary ammonium (GQA) groups have shown enhanced cellular uptake and efficient drug delivery, while the incorporation of poly(ethylene glycol) (PEG) corona can potentially reduce the absorption of cationic carriers by opsonic proteins and subsequent uptake by mononuclear phagocytic system (MPS). To understand the interactions of GQA and PEG groups and their effects on the biophysicochemical characteristics of nanocarriers, a series of polyurethane micelles containing GQA and different molecular weights of PEG were prepared and carefully characterized. It was found that the GQA and PEG groups are unevenly distributed on the micellar surface to form two kinds of hydrophilic domains. As a result, the particle surface with some defects cannot be completely shielded by the PEG corona. Despite this, the longer PEG chains with a brush conformation provide superior stabilization and steric repulsion against the absorption of proteins and, thus, can reduce the cytotoxicity, protein absorption, and MPS uptake of micelles to some extent. This study provides a new understanding on the interactions between PEG chains and cationic groups and a guideline for the design and fabrication of safe and effective drug delivery systems.

Folate Receptor Targeted Delivery of siRNA and Paclitaxel to Ovarian Cancer Cells via Folate Conjugated Triblock Copolymer to Overcome TLR4 Driven Chemotherapy Resistance.

This paper focuses on the ability of a folate-decorated triblock copolymer to deliver a targeted dose of siRNA in order to overcome chemotherapy resistance which can commonly cause complications in ovarian cancer patients. The micelleplexes that are formed upon electrostatic interaction with siRNA are used to deliver siRNA in a targeted manner to SKOV-3 ovarian cancer cells that overexpress folate receptor-α (FRα). The triblock copolymer consists of polyethylenimine-graft-polycaprolactone-block-poly(ethylene glycol) (PEI-g-PCL-b-PEG-Fol). In this work, polymers of different molecular weights of PEG, as well as different grafting degrees of the (g-PCL-b-PEG-Fol) chains to PEI, were analyzed to optimize targeted siRNA delivery. The polymers, their micelleplexes, and the in vitro performance of the latter were characterized by nuclear magnetic resonance, dynamic light scattering, transmission electron microscopy, flow cytrometry, western blot, confocal microscopy, and in luciferase assays. The different PEI-g-PCL-b-PEG-Fol conjugates showed suitable sizes below 260 nm, especially at N/P 5, which also allowed for full siRNA condensation. Furthermore, flow cytometry and Western blot analysis demonstrated that our best polymer was able to effectively deliver siRNA and that siRNA delivery resulted in efficient protein knockdown of toll-like receptor 4 (TLR4). Consequently, TLR4 knock down within SKOV-3 cells resensitized them toward paclitaxel (PTX) treatment, and apoptotic events increased. This study demonstrates that PEI-g-PCL-b-PEG-Fol conjugates are a reliable delivery system for siRNA and are able to mediate therapeutic protein knockdown within ovarian cancer cells. Additionally, this study provides further evidence to link TLR4 levels to chemotherapy resistance.

Effects of PEG molecular weight on its interaction with albumin

The fluorescence property of bovine serum albumin was investigated in the presence of PEGs of different molecular weights. Based on our results, we propose that PEGs of different molecular weights bind to albumin in the pH 7.4 aqueous solution, but only when the polymer size is larger than the protein size, one polymer chain may bind to multiple proteins and cause the proteins to aggregate.

Poly(ethylene glycol) grafted multi-walled carbon nanotubes/LiFePO4 composite cathodes for lithium ion batteries

Abstract Poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (MWCNTs-g-PEG or MP) were synthesized and used to modify LiFePO4 as cathodes for lithium-ion batteries (LIBs). The effects of different molecular weights of PEG grafted on MWCNTs and different mass fractions of MP on the properties of LiFePO4/MP composite cathodes were evaluated by their morphology, charge–discharge tests, electrochemical impedance spectroscopy, electrical and thermal conductivities. Their electrochemical behaviors at ambient temperature and low temperature, high rate capability and cycling performance were observed in the presence of the MP additives. The lithium ions diffusion in the LiFePO4/MP composite electrodes was almost 2 orders of magnitude higher than that in the LiFePO4/acetylene black (AB) electrode when the conductive additive content was 5 wt.%. Thermal studies of LiFePO4/MP were also examined by the heat-pole method, which showed higher thermal conductivity of the cathode in cases of MP being incorporated into LiFePO4 particles than LiFePO4 cathodes with AB or MWCNTs additives. These results suggest that MP is a promising conductive additive to increase the electrochemical performances, thermal transport and safety of LiFePO4 cathodes for LIBs.