PEG Mw Research Articles

Effect of molecular weight of PEG or PVA as reducing-stabilizing agent in the green synthesis of silver-nanoparticles

Silver nanoparticles (Ag-NPs) have been prepared by a green chemistry method using PEG or PVA, as reducing-stabilizing agent, and characterized using UV–vis, SEM-EDS, AFM and TEM. A comparative study was done to determine the PEG or PVA molecular weight (Mw) effect, on shape, size and dispersity of Ag-NPs. Lower Mw of PEG or PVA results in small Ag-NPs. The synthesized Ag-NPs were spherical with an average size of 2–30nm (PEG measured by TEM), and 2.5–45nm (PVA measured by TEM). Furthermore, photocatalytic degradation of Putnam sky-blue 39 was measured spectrophotometrically using Ag-NPs under sun light illumination, with 97% efficiency.

Influence of PEGylation on nanoparticle mobility in different models of the extracellular matrix

Nanoparticle transport inside the extracellular matrix (ECM) is a crucial factor affecting the therapeutic success. In this work, two in vitro ECM models – a neutrally charged collagen I network with an effective pore size of 0.47μm and Matrigel, a basement membrane matrix with strong negative charge and effective pore size of 0.14μm – were assessed for barrier function in the context of diffusing nanoparticles. Nanoparticles with a size of 120nm were coated with poly(ethylene glycol) (PEG) of different molecular weights – 2, 5 and 20kDa – over a range of gradually increasing coating densities – precisely 0.2, 2, 8 and 20PEG/nm2. The PEG corona was imaged in its native state without any drying process by atomic force microscopy, revealing that the experimentally determined arrangement of PEG at the surface did not match with what was theoretically expected. In a systematic investigation of nanoparticle mobility via fluorescence recovery after photobleaching, increasing both PEG MW and PEGylation density gradually improved diffusion properties predominately in collagen. Due to its smaller pore size and electrostatic obstruction, diffusion coefficients were about ten times lower in Matrigel than in the collagen network and an extension of the PEG MW and density did not necessarily lead to better diffusing particles. Consequently, collagen gels were revealed to be a poor model for nanoparticle mobility assessment, as neither their pore size nor their electrostatic properties reflect the expected in vivo conditions. In Matrigel, diffusion proceeded according to a sigmoidal increase with gradually increasing PEG densities showing threshold zeta potentials of 11.6mV (PEG2kDa) and 13.8mV (PEG5kDa), below which particles were regarded as mobile. Irrespective of the molecular weight particles with a PEGylation density lower than 2PEG/nm2 were defined as immobile and those with a PEG coverage of more than 8PEG/nm2 as mobile.

A mechanically robust injectable hydrogel scaffold for adipose-derived stem cell delivery for the treatment of peripheral arterial disease

Event Abstract Back to Event A mechanically robust injectable hydrogel scaffold for adipose-derived stem cell delivery for the treatment of peripheral arterial disease Stuart Young1, Lauren E. Flynn2 and Brian G. Amsden1 1 Queen's University, Department of Chemical Engineering, Canada 2 University of Western Ontario, Department of Chemical and Biochemical Engineering, Canada Introduction: Peripheral arterial disease can lead to critical limb ischemia with high risks of amputation and mortality. A promising treatment involves delivering adipose-derived stem cells (ASCs) to stimulate revascularization and functional recovery. However, when delivered via intramuscular injection in saline, substantial ASC loss occurs. To improve ASC retention and survival, a modular delivery gel was developed composed of: i) methacrylated glycol chitosan (MGC) functionalized with GGGGRGDS, and ii) a diacrylate triblock copolymer of poly(ethylene glycol) (PEG) and poly(trimethylene carbonate) (PTMC) to improve mechanical robustness. A thermal initiator system of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) was optimized for in situ gelation following injectable delivery. Methods: MGC was prepared as previously reported[1]. The N terminus of GGGGRGDS peptide was acrylated and conjugated to MGC via Michael addition. Acrylated PEG-PTMC of varying block lengths was prepared by ring-opening polymerization of TMC initiated by PEG (4, 10, or 20 kg·mol-1) (TMC:PEG MW = 1:10 – 1:2)) using HCl as a monomer activator, followed by reaction with acryloyl chloride. Polymer structure and functionalization were confirmed by 1H NMR and GPC. To form gels, APS and TEMED (2.5 to 10 mM) were added to solutions of MGC and PEG-PTMC. Initiation sensitivity and crosslinking time were assessed by rheometry at 20 °C and 37°C. Gels were equilibrated in PBS, after which the swelling ratio and mechanical properties were measured. Isolated bovine ASCs[2], expanded to passage 2, were suspended in the pre-polymer solutions. APS/TEMED was added, and the suspension injected via 25G needle into molds and crosslinked by heating (37°C). ASC viability (LIVE/DEAD staining) and metabolic activity (MTT assay) were monitored over 7 days. Results: The MGC had a 5% degree of methacrylation and 5% degree of peptide functionalization, while the PEG-PTMC had > 99% acrylation. Pre-polymer solutions showed no gelation over 10 min at 20 °C (Fig. 1a). Upon heating, gelation time was directly related to initiator concentration (Fig. 1b). The swelling, equilibrium compressive modulus, and maximum strain of PEG-PTMC hydrogels was dependent on the overall molecular weight and PEG/PTMC ratio (Fig. 2). By blending MGC with PEG-PTMC, gel stiffness was significantly reduced to the range of native tissue (~10-15 kPa), while improving elastic resiliency under dynamic loading. Further, the metabolic activity of encapsulated ASCs was maintained over 7 d of culture. Discussion: Blending of MGC with PEG-PTMC facilitated adjustment of gel mechanical properties while improving resiliency under dynamic loading. The APS/TEMED crosslinking approach provided an injectable delivery method with high stimuli sensitivity. Sustained ASC metabolic activity in culture suggests the gel could promote ASC survival and retention, thereby promoting their regenerative effects in ischemic regions.

Enhancement of lignosulfonate-based polyoxyethylene ether on enzymatic hydrolysis of lignocelluloses

Effect of the molecular structure of lignosulfonate-based polyoxyethylene ether (LS-PEG) on the enzymatic hydrolysis of Avicel and corn stover was investigated. With the increase of PEG contents and Mw of LS-PEG, glucose yield of corn stover increased from 16.7% to 51.9%. When LS-PEG was compounded with cationic surfactant cetyltrimethylammonium bromide (CTAB), the enhancement of glucose yield of corn stover was further increased from 45.3% to 62.8%. Sulfonic group of LS-PEG preferentially interacted with quaternary ammonium group of CTAB by the electrostatic attraction to form a similar non-ionic surfactant CTAB-LS-PEG. CTAB-LS-PEG showed electrically neutral and more hydrophobic, and blocked more nonproductive adsorption of cellulase on the lignin. Therefore, CTAB-LS-PEG enhanced enzymatic hydrolysis efficiency of lignocelluloses more significantly. The understanding developed in this study can help to develop potential approaches and strategies for effective application of lignosulfonate to improve bioconversion of lignocellulosic biomass.

Structure and Compatibility Study of Modified Polyurethane/Fe<sub>3</sub>O<sub>4</sub> Nanocomposite for Shape Memory Materials

Shape Memory Polymer (SMP) is one of smart materials class that has the ability to recall a given shape before deformation in the transient state. The development of SMP is dominated by polyurethane which is currently focused on the optimization of manufacturing-related research (ease of processing), and the extraction of the potential for biomedical applications. In this study, Shape Memory Polyurethane (SMPU) with Polyethylene Glycol-based material (PEG mw: 6000) as soft segment, 4,4'-Methylenebis (Cyclohexyl isocyanate) (HMDI) as a hard segment and 1,1,1-Trimethylol propane (TMP) as a chain extender were used as a candidate for Vascular Stents. Materials used for the fillers were nano particles of magnetite (Fe3O4) which have 20–50 nm diameters. Variations of the composition were used as a variable. Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) were conducted to investigate the polymer chains which were formed during polymerization, Field Emission Scanning Electron Microscopy (FE-SEM) was used to analyze the interface between the filler and the composite matrix. Manual physical actuation was conducted to analyze the physical recovery and transition temperature of the SMPU. Composition and fillers effect on the performance of SMPU composite were discussed in detail along with analysis of its structure and molecular design.

Plasticizing effect of poly(ethylene glycol)s with different molecular weights in poly(lactic acid)/starch blends

ABSTRACTBinary and ternary blends composed of poly(lactic acid) (PLA), starch, and poly(ethylene glycols) (PEGs) with different molecular weights (weight‐average molecular weights = 300, 2000, 4000, 6000, and 10, 000 g/mol) were prepared, and the plasticizing effect and miscibility of PEGs in poly(lactic acid)/starch (PTPS) or PLA were intensively studied. The results indicate that the PEGs were effective plasticizers for the PTPS blends. The small‐molecule plasticizers of PEG300 (i.e., the Mw of PEG was 300g/mol) and glycerol presented better plasticizing effects, whereas its migration and limited miscibility resulted in significant decreases in the water resistance and elongation at break. PEG2000, with a moderate molecular weight, was partially miscible in sample PTPS3; this led to better performance in water resistance and mechanical properties. For higher molecular weight PEG, its plasticization for both starch and PLA was depressed, and visible phase separation also occurred, especially for PTPS6. It was also found that the presence of PEG significantly decreased the glass‐transition temperature and accelerated the crystallization of the PLA matrix, depending on the PEG molecular weight and concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41808.

Potential Evaluation of PVA-Based Hydrogels for Biomedical Applications

P oly vinyl alcohol PVA -based hydrogels prepared using freeze/thawing treatment have become increasingly important biomaterials for biomedical applications having great properties such as biocompatibility, biodegradability and high water absorbency. In this study, PVA-based physically cross-linked hydrogels were prepared with and without the presence of poly ethylene glycol PEG freezing at -16 °C for 16 h and thawing at room temperature for 8 h. The focus of this work was to address the effect of the addition of PEG Mw: 2000 or 5000 and the effect of the number of freezing/thawing cycles on swelling behaviour. The Scanning Electron Microscopy SEM measurements demonstrated the morphological characteristics of PVA-based hydrogels indicating the formation of the macroporosity fabricated during freeze/thawing process. From the swelling tests undertaken it w as apparent that all the hydrogels exhibited unique swelling characteristics having high swelling degree at all pH values such as pH 2.1, 5.5 and 7.4 representing the pH values of stomach, blood and dermis. Thus, the hydrogels synthesized in this study present important potential for biomedical applications

ChemInform Abstract: Ultrasounds in Melted Poly(ethylene Glycol) Promote Copper‐Catalyzed Cyanation of Aryl Halides with K4[Fe(CN)6

Melted poly(ethylene glycols) (PEGs) were used for the first time as solvent for the sonochemically promoted cyanation of aryl halides employing inexpensive and safe K4[Fe(CN)6] and a relatively low amount of Cu-based catalyst. The Mw (weight-average polymer molecular weight) of PEG proved to notably influence the substrate conversion, which is indicative of a strong dependence of the sonication efficacy on solvent properties. Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) contributed to the characterization of the polymer and the elucidation of the catalytic system.

Enhanced Formation of Stereocomplex Crystallites of High Molecular Weight Poly(l-lactide)/Poly(d-lactide) Blends from Melt by Using Poly(ethylene glycol)

Melt processing of polymers is preferable in industry. Unfortunately, for high molecular weight (Mw) poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blends, exclusive formation of stereocomplex (sc) crystallites from the melt has never been achieved. We proposed a new and simple approach to enhance the melt crystallization of sc crystallites from high Mw PLLA/PDLA by using poly(ethylene glycol) (PEG). The crystallizability of the PLLA/PDLA blend is greatly enhanced by PEG during crystallization from the melt. The resulted crystalline structures depend on the Mw and content of PEG, and the crystallinity of sc crystallites increases with increasing content or decreasing Mw of PEG. More importantly, exclusive formation of sc crystallites is achieved in the blends with 10% PEG having Mw values of 1000 or 2000 g mol–1. Polarized optical microscopy (POM) observation shows that the spherulitic growth rates of sc crystallites are accelerated. The results demonstrate that segmental mobility of polylactides (PLA) chains plays a dominant role on the formation of sc crystallites from melt and provide a simple way to prepare sc crystallites from high Mw PLA by melt blending and enlarge the applications of PLA.

'Stealth' lipid-based formulations: poly(ethylene glycol)-mediated digestion inhibition improves oral bioavailability of a model poorly water soluble drug.

For over 20years, stealth drug delivery has been synonymous with nanoparticulate formulations and intravenous dosing. The putative determinants of stealth in these applications are the molecular weight and packing density of a hydrophilic polymer (commonly poly(ethylene glycol) (PEG)) that forms a steric barrier at the surface of the nanoparticle. The current study examined the potential translation of the concepts learned from stealth technology after intravenous administration to oral drug delivery and specifically, to enhance drug exposure after administration of oral lipid-based formulations (LBFs) containing medium-chain triglycerides (MCT). MCT LBFs are rapidly digested in the gastrointestinal tract, typically resulting in losses in solubilisation capacity, supersaturation and drug precipitation. Here, non-ionic surfactants containing stealth PEG headgroups were incorporated into MCT LBFs in an attempt to attenuate digestion, reduce precipitation risk and enhance drug exposure. Stealth capabilities were assessed by measuring the degree of digestion inhibition that resulted from steric hindrance of enzyme access to the oil-water interface. Drug-loaded LBFs were assessed for maintenance of solubilising capacity during in vitro digestion and evaluated in vivo in rats. The data suggest that the structural determinants of stealth LBFs mirror those of parenteral formulations, i.e., the key factors are the molecular weight of the PEG in the surfactant headgroup and the packing density of the PEG chains at the interface. Interestingly, the data also show that the presence of labile ester bonds within a PEGylated surfactant also impact on the stealth properties of LBFs, with digestible surfactants requiring a PEG Mw of ~1800g/mol and non-digestible ether-based surfactants ~800g/mol to shield the lipidic cargo. In vitro evaluation of drug solubilisation during digestion showed stealth LBFs maintained drug solubilisation at or above 80% of drug load and reduced supersaturation in comparison to digestible counterparts. This trend was also reflected in vivo, where the relative bioavailability of drug after administration in two stealth LBFs increased to 120% and 182% in comparison to analogous digestible (non-stealth) formulations. The results of the current study indicate that self-assembled "stealth" LBFs have potential as a novel means of improving LBF performance.

PEGylated, NH2-Terminated PAMAM Dendrimers: A Microscopic View from Atomistic Computer Simulations

Poly(amido amine) (PAMAM) dendrimers are promising nanocarriers in a wide range of biomedical applications including gene and drug delivery and as imaging agents. They have unique structural properties and are characterized by high size uniformity, low polydispersity, and a large number of modifiable surface groups. Drug-dendrimer systems are usually further modified through the conjugation of ligands in order to confer the carriers' specific characteristics designed to enhance their efficacy. The chemistry and structure of the solvated ligand-conjugated dendrimer nanocarriers (DNCs) will dictate how they interact with the physiological environment and, therefore, their fate and function. Understanding the microstructures of ligand-conjugated DNCs is, therefore, of great relevance within the context of drug delivery applications. In this work, we investigate the effect of poly(ethylene glycol) (PEG) on the microstructure of solvated, NH2-terminated PAMAM DNCs using fully atomistic molecular dynamics simulations. Several variables including dendrimer generation (2-5), PEGylation density (0-50%), and PEG Mw (500 and 1000) were investigated. The results obtained showed a good match with available experimental results, including size as a function of dendrimer degeneration (G2NH2-G5NH2). No back-folding is observed for PAMAM dendrimers with generation lower than G5NH2. G2NH2 and G3NH2 showed a dense-packed, nonglobular structure, and G4NH2 and G5NH2 have a segmented, "open" structure. Our results help settle a long-standing debate with respect to "back-folding" as the microstructural information obtained here is reconciled with experimental results. PEGylation was found to influence the microstructure in a different way, including an expected increase in the overall size of the DNCs, while not affecting much the solvation of unmodified terminal (primary) amines. It also serves to expand the core of dendrimers, reduce the surface charge, and change solvation behavior of different generation branching amines. We show that the microstructure of a PEG layer with the same number of repeat units can be significantly altered by changing the grafting density and size of PEG. Potential consequences in the design of PEGylated dendrimers for drug delivery and targeting are discussed based on the obtained microstructural information.

Ultrasounds in Melted Poly(ethylene glycol) Promote Copper‐Catalyzed Cyanation of Aryl Halides with K4[Fe(CN)6

Melted poly(ethylene glycols) (PEGs) were used for the first time as solvent for the sonochemically promoted cyanation of aryl halides employing inexpensive and safe K4[Fe(CN)6] and a relatively low amount of Cu-based catalyst. The Mw (weight-average polymer molecular weight) of PEG proved to notably influence the substrate conversion, which is indicative of a strong dependence of the sonication efficacy on solvent properties. Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) contributed to the characterization of the polymer and the elucidation of the catalytic system.

Hybrid nanocomposites based on POSS and networks of methacrylated camelina oil and various PEG derivatives

Several photo‐curable hybrid systems based on methacrylate‐modified camelina oil (CO) were synthesized through a copolymerization reaction with hydrophilic dimethacrylated poly(ethylene glycol) macromonomers (PEG MW = 300, 550, and 750 g/mol). In a first step, the epoxidation and subsequently the methacrylation reactions of CO were performed and monitorized using 1H NMR and FTIR. Further, the polymerization reaction of the new synthesized oil‐based monomer under visible light was proved by FTIR. The chain length of methacrylate functionalized PEG was found to directly influence some key properties of the oil‐based networks. The curing performance of the systems was studied by GF measurements. Water uptake capacity tests and contact angle measurements were undertaken and it was found that the internal arrangement of components is strongly affecting the hydrophilicity of the materials. Furthermore, nanostructured polyhedral oligomeric silsesquioxane (POSS) compounds bearing one or eight methacrylated groups were selected in order to obtain innovative organic–inorganic nanocomposites. Mechanical and thermal properties were evaluated by compression tests, DMA, TGA, and also the morphology of the synthesized materials was investigated by SEM.Practical applications: Tailoring the copolymer composition and the reinforcing agent in the manufacturing process leads to a wide range of products with optimum properties suitable for use in a variety of industrial areas. Well‐defined oil‐derived systems with controllable compressive strength were prepared in this work covering the whole range, from a hard material (with short chain PEG) to a soft and flexible one (with long chain PEG).

Targeted gene delivery by polyplex micelles with crowded PEG palisade and cRGD moiety for systemic treatment of pancreatic tumors

Adequate retention in systemic circulation is the preliminary requirement for systemic gene delivery to afford high bioavailability into the targeted site. Polyplex micelle formulated through self-assembly of oppositely-charged poly(ethylene glycol) (PEG)-polycation block copolymer and plasmid DNA has gained tempting perspective upon its advantageous core–shell architecture, where outer hydrophilic PEG shell offers superior stealth behaviors. Aiming to promote these potential characters toward systemic applications, we strategically introduced hydrophobic cholesteryl moiety at the ω-terminus of block copolymer, anticipating to promote not only the stability of polyplex structure but also the tethered PEG crowdedness. Moreover, Mw of PEG in the PEGylated polyplex micelle was elongated up to 20 kDa for expecting further enhancement in PEG crowdedness. Furthermore, cyclic RGD peptide as ligand molecule to integrin receptors was installed at the distal end of PEG in order for facilitating targeted delivery to the tumor site as well as promoting cellular uptake and intracellular trafficking behaviors. Thus constructed cRGD conjugated polyplex micelle with the elevated PEG shielding was challenged to a modeled intractable pancreatic cancer in mice, achieving potent tumor growth suppression by efficient gene expression of antiangiogenic protein (sFlt-1) at the tumor site.

Aggregation of a model porphyrin within poly(ethylene glycol) (PEG): effect of water, PEG molecular weight, ionic liquids, salts, and temperature

Understanding molecular aggregation within environmentally-benign media is of utmost importance. Aggregation of a common porphyrin, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TSPP), dissolved in media composed of poly(ethylene glycols) (PEGs) up to an average molecular weight (MW) of 8000 as major components, is investigated. J-aggregates of TSPP are well-manifested via the bathochromically-shifted UV-vis absorbance band of TSPP. As media, 10 wt% water-added PEGs at pH 1 show excellent efficiency for TSPP J-aggregation. The J-aggregation efficiency increases as the PEG MW is increased and it is found to be the maximum for the medium constituted of PEG3000. Once formed, some of the J-aggregates decay back to the diprotonated form via pseudo-first order kinetics. Addition of salts NaCl and NaBF4 and ionic liquids [bmim][PF6], [bmim][Tf2N], [bmim][BF4], and [bmim][OTf] [bmim = 1-butyl-3-methylimidazolium, PF6 = hexafluorophosphate, Tf2N = bis(trifluoromethylsulfonyl)imide, BF4 = tetrafluoroborate, and OTf = trifluoromethanesulfonate], respectively, to TSPP dissolved in 10 wt% water added PEGs at pH 1 results in increased J-aggregation efficiency. Ionic liquids are found to protect porphyrin J-aggregates from decaying to their diprotonated form. Increasing temperature from ambient to 90 °C results in decreased J-aggregation efficiency of TSPP in the presence of salts NaCl and NaBF4, respectively; concentration of J-aggregates does not change much with temperature when an ionic liquid as an additive is present in the medium. The polymer chain length and electrostatic interactions appear to play a major role in porphyrin J-aggregation efficiency and kinetics within water-added acidic mixtures of PEG.

Solvation Structure of Poly(ethylene glycol) in Ionic Liquids Studied by High-energy X-ray Diffraction and Molecular Dynamics Simulations

Solvation structures of poly(ethylene glycol) (PEG) in 1-ethyl-3-methylimidazolium-based ionic liquids solution were studied by using high-energy X-ray diffraction (HEXRD) and molecular dynamics (MD) simulation in terms of dependences on the anion-type for ILs, molecular weight (Mw), concentration and shape (linear or tetra-armed) for PEG. It was found from HEXRD experiment that there is no Mw and shape dependences for PEG in 1-ethyl-3-methylimidazolium bis(trifluoromethansulfonyl)amide, [C2mIm+][TFSA–] solution, implying that the local structure (r < 15 Å) is not influenced by Mw and shape of PEG. From the HEXRD results with the aid of MD simulations, it was found that C2mIm cation preferentially solvates to PEG in all the ILs, and TFSA is distributed randomly with van der Waals and weak electrostatic interactions. The atom–atom pair correlation and space distribution functions evaluated from the MD simulations revealed that hydrogen bonding interactions are formed between C2 carbon within the imidazolium ring and O (PEG), which is essentially different from C4 carbon–O and C5 carbon–O interactions. Finally, we discussed the relationship between the obtained microscopic solvation structures and the macroscopic properties of PEG-based gel (swelling ratio and χ parameters).

Solvent Effect in PLA‐PEG Based Nanoparticles Synthesis through Surfactant Free Polymerization

AbstractSummary: In this work one‐pot synthesis of PEGylated PLA‐based nanoparticles (NPs) without using any surfactant has been performed. Adopting ring opening polymerization of L,L–Lactide and 2‐hydroxyethyl methacrylate (HEMA), vinyl end functionalized poly(lactic acid) macromonomers (HEMA‐LAn) have been produced with tunable number of lactic acid units (larger than 5) and a low molecular weight distribution. Macromonomers have been further copolymerized with modified PEG chains (HEMA‐PEGm) through a monomer starved semi‐batch emulsion polymerization performed without using any surfactant. In these conditions, small and monodispersed NPs of around 150 nm are obtained. Since macromonomers with n larger than 5 are highly viscous at room temperature, they have to be dissolved in a solvent before their injection in the reactor. In this work the effects in changing the solvent adopted in the starved process (water miscible or non‐miscible) and its amount have been investigated. Moreover, the effect of both PEG chains concentration and MW on the final NPs properties has been elucidated. The colloidal stability of the NPs produced using different solvents has been verified in phosphate buffered saline (PBS) solution via dynamic light scattering measurements; in addition the critical coagulation concentration of these PEGylated NPs has been determined.

Liquid-Liquid Equilibrium of Poly(Ethylene Glycol) 6000 + Sodium Succinate + Water System at Different Temperatures

Phase diagrams and the compositions of coexisting phases of poly(ethylene glycol) (PEG) 6000 + sodium succinate + water system have been determined experimentally at 298.15, 308.15, and 318.15 K. The effects of temperature on the binodal curve and tie lines have been studied. The binodal curves were successfully fitted to a nonlinear equation relating the concentrations of PEG 6000 and sodium succinate, and the coefficients were estimated for the formentioned systems (low AARD, high R 2, and low SD). Tie-line compositions were estimated and correlated using Othmer-Tobias and Bancroft equations, and the parameters were reported. The effect of temperature on the phase-forming ability has been studied by fitting the binodal data to a Setschenow-type equation for each temperature. The effective excluded volume (EEV) values were also calculated from the binodal data, and it was found out that the values increased with an increase in the temperature. Furthermore, the effect of MW of PEG on the phase diagram has been studied and verified.

Polymorph and Morphology Control of CaCO3 via Temperature and PEG During the Decomposition of Ca(HCO3)2

As research continues, the control on the polymorph and morphology of calcium carbonate (CaCO3) becomes a hot topic because its application is limited by these parameters. The polymorph and morphology control of CaCO3 was successfully achieved via temperature and PEG (Mw = 6000) during the decomposition of Ca(HCO3)2, which has rarely been employed to prepare precipitated CaCO3. As‐prepared CaCO3 was characterized using XRD and SEM. In the case of no PEG, rhombohedra calcite, lamellar vaterite, rod‐ and needlelike aragonite are observed, and calcite is the major phase at all samples and it increases with temperature, whereas vaterite and aragonite decrease with temperature. The addition of PEG restrains the formation of vaterite and promotes the emergence of needlelike aragonite particles at 70°C, and prevents the generation of calcite and encourages the production of rodlike aragonite particles at 80°C and 90°C. This work not only provides a new way on the preparation of CaCO3 powder but also presents the feasible control method in this route.

Endosomal escape and transfection efficiency of PEGylated cationic liposome–DNA complexes prepared with an acid-labile PEG-lipid

Cationic liposome–DNA (CL–DNA) complexes are being pursued as nonviral gene delivery systems for use in applications that include clinic trials. However, to compete with viral vectors for systemic delivery in vivo, their efficiencies and pharmacokinetics need to be improved. The addition of poly (ethylene glycol)-lipids (PEGylation) prolongs circulation lifetimes of liposomes, but inhibits cellular uptake and endosomal escape of CL–DNA complexes. We show that this limits their transfection efficiency (TE) in a manner dependent on the amount of PEG-lipid, the lipid/DNA charge ratio, and the lipid membrane charge density. To improve endosomal escape of PEGylated CL–DNA complexes, we prepared an acid-labile PEG-lipid (HPEG2K-lipid, PEG MW 2000) which is designed to lose its PEG chains at the pH of late endosomes. The HPEG2K-lipid and a similar but acid-stable PEG-lipid were used to prepare PEGylated CL–DNA complexes. TLC and dynamic light scattering showed that HPEG2K-CL–DNA complexes are stable at pH 7.4 for more than 24 h, but the PEG chains are cleaved at pH 5 within 1 h, leading to complex aggregation. The acid-labile HPEG2K-CL–DNA complexes showed enhanced TE over complexes stabilized with the acid-stable PEG-lipid. Live-cell imaging showed that both types of complexes were internalized to quantitatively similar particle distributions within the first 2 h of incubation with cells. Thus, we attribute the increased TE of the HPEG2K-CL–DNA complexes to efficient endosomal escape, enabled by the acid-labile HPEG2K-lipid which sheds its PEG chains in the low pH environment of late endosomes, effectively switching on the electrostatic interactions that promote fusion of the membranes of complex and endosome.