Bearing Poly Ethylene Glycol Research Articles

Liquid Based Circularly Polarized Phosphorescence of a Chiral Schiff Base Platinum(II) Complex Bearing Polyethylene Glycol Chains

AbstractA chiral Schiff base platinum(II) complex1bearing polyethylene glycol (PEG) chains was synthesized. The complex was found to melt at 44 °C whereas its non‐substituted analogue2has a high melting point (>300 °C). Upon cooling after melting, the complex remained liquid at room temperature over 30 minutes and exhibited yellow phosphorescence. Circularly polarized phosphorescence (CPP) properties were examined and it was found that the absolute value of the luminescence dissymmetry factor (glum) increases significantly in the liquid state compared to the dilute solution state. Herein, we report the first example of CPP from solvent‐free supercooled liquids.

Self-Organization of Mobile, Polyelectrolytic Dendrons on Stable, Amphiphile-Based Spherical Surfaces.

Spherical surfaces bearing mobile, solvophilic chains are ubiquitous. These systems are found in nature in the form of biological cells bearing carbohydrate chains, or glycans, or in drug delivery systems such as vesicles bearing polyethylene glycol chains and carrying therapeutic molecules. The self-organization of the chains on the spherical surface dictates the stability and functionality of the latter and is determined by key factors such as the interchain, chain-surface interactions, excluded volume, concentration of the chains, and external environment. This study develops a fundamental understanding of how these factors control the organization of mobile, solvophilic chains while preserving the stability of the spherical surface. To that end, the study focuses on the organization of polyamidoamine dendrons on the surface of a dipalmitoylphosphatidylcholine-based vesicle. The excluded volume of the chains and the external environment are, respectively, controlled via the dendron generation and the pH. For acidic and basic pH environments, the dendrons are extended away from the surface. As a consequence, the vesicles are able to accommodate significantly higher concentration of dendrons on their surface without rupturing. For acidic pH, the dendrons change their conformation to avoid intermeshing. However for basic pH, the dendrons only change their conformation at extremely high concentrations due to excluded volume effects. These conformational changes are attributed to the number of protonated dendron residues that vary as a function of pH. The results from this study will advance diverse subdisciplines within cell biology, biomedicine, and pharmaceuticals.

Iminopyridyl ligands bearing polyethylene glycol unit for nickel catalyzed ethylene polymerization

Influence of polyethylene glycol unit on nickel catalyzed ethylene polymerization have attracted increasing interest. The Lewis basic oxygen atoms on polyethylene glycol group can form interactions with Lewis acidic metal additives. In this contribution, a series of iminopyridyl ligands (L-O1, L-O2 and L-O3) bearing polyethylene glycol units and corresponding nickel complexes (Ni-O1, Ni-O2 and Ni-O3) were designed, synthesized and characterized. By the activation of alkylaluminium cocatalysts, the nickel complexes and their corresponding MgCl2-supported nickel precatalysts (Ni-O1-Mg, Ni-O2-Mg and Ni-O3-Mg) were investigated in catalytic homogeneous and heterogeneous ethylene polymerization, respectively. The molecular weight of products increased with the number of oxygen atoms on polyethylene glycol unit increasing. The introduction of the MgCl2 support resulted in much higher molecular weights and much lower branched densities of polyethylenes than those of products generated in the homogeneous polymerizations. The polymers generated in heterogeneous polymerizations have excellent polymer powder morphology to prevent reactor fouling, facilitating potential industrial applications.

Fmoc-PEG Coated Single-Wall Carbon Nanotube Carriers by Non-covalent Functionalization: An Experimental and Molecular Dynamics Study.

Due to their structural characteristics at the nanoscale level, single-walled carbon nanotubes (SWNTs), hold great promise for applications in biomedicine such as drug delivery systems. Herein, a novel single-walled carbon nanotube (SWNT)-based drug delivery system was developed by conjugation of various Fmoc-amino acid bearing polyethylene glycol (PEG) chains (Mw = 2,000, 5,000, and 12,000). In the first step, full-atom molecular dynamics simulations (MD) were performed to identify the most suitable Fmoc-amino acid for an effective surface coating of SWNT. Fmoc-glycine, Fmoc-tryptophan, and Fmoc-cysteine were selected to attach to the PEG polymer. Here, Fmoc-cysteine and -tryptophan had better average interaction energies with SWNT with a high number of aromatic groups, while Fmoc-glycine provided a non-aromatic control. In the experimental studies, non-covalent modification of SWNTs was achieved by Fmoc-amino acid-bearing PEG chains. The remarkably high amount of Fmoc-glycine-PEG, Fmoc-tryptophan-PEG, and Fmoc-cysteine-PEG complexes adsorbed onto the SWNT surface, as was assessed via thermogravimetric and UV-vis spectroscopy analyses. Furthermore, Fmoc-cysteine-PEG5000 and Fmoc-cysteine-PEG12000 complexes displayed longer suspension time in deionized water, up to 1 and 5 week, respectively, underlying the ability of these surfactants to effectively disperse SWNTs in an aqueous environment. In vitro cell viability assays on human dermal fibroblast cells also showed the low cytotoxicity of these two samples, even at high concentrations. In conclusion, synthesized nanocarriers have a great potential for drug delivery systems, with high loading capacity, and excellent complex stability in water critical for biocompatibility.

Hybrid nanosilicas produced by the Stöber sol-gel process: In vitro evaluation in MRC-5 cells

A series of 12 organosilanes exhibiting different steric and electronic properties were employed in the synthesis of hybrid silicas by the Stöber sol-gel process. The resulting materials were characterized by a set of complementary techniques (nitrogen adsorption, dynamic light scattering, small-angle X-ray scattering, transmission electron microscopy, and carbon content analysis).. Hybrid silicas bearing polyethylene glycol (PEG), zwitterion (ZWT), and methyl (C1) moieties improved the physical-chemical properties of the nanoparticles for biological applications. Toxicological safety tests were performed on the fibroblast cell line (MRC-5), which showed that the functionalization of silica nanoparticles with PEG and ZWT increased cell viability, 111 ± 8.5% and 114 ± 6.3%, respectively, when compared to that of nanomaterials without functionalization, 98 ± 8.8%. Both functionalized and non-functionalized silica nanoparticles did not cause any damage to the DNA of the cells, even at the highest doses.

Light‐Switching Azo‐Copolymers Self‐Assembly in Multi‐Stationary States

In the present research, novel tri-block-copolymers bearing polyethylene glycol (PEG), azobenzene (Azo), and tetra-ortho-methoxy-substituted Azo (mAzo) segments are synthesized and explored. Light-controlled PEG-PmAzo-PAzo self-assemblies switching between multi-stationary states is realized. Under controlling of UV, blue, green, and red light, PEG-PmAzo-PAzo isomerize between 4 photostationary states. The enrichment of cis isomers of Azo and mAzo induces the self-assembly of PEG-PmAzo-PAzo in toluene. The morphologies and scale of the self-assemblies can be switched between four stationary states, which are investigated by dynamic light scattering, scanning electron microscopy, and transmission electron microscopy.

Improvement of surface hydrophilicity and biological sample-compatibility of molecularly imprinted polymer microspheres by facile surface modification with α-cyclodextrin

Molecularly imprinted polymers (MIPs) compatible with complex biological samples hold much promise in many bioanalytical and biomedical applications and development of new strategies for obtaining such advanced synthetic receptors is thus of high interest. Herein, a facile and efficient new approach is presented for the preparation of MIP microspheres capable of selectively recognizing small organic analyte in the complex biological sample, which involves the simple surface modification of MIP particles bearing polyethylene glycol (PEG) brushes with α-cyclodextrin (α-CD). The proof-of-principle was demonstrated by the first synthesis of propranolol-imprinted polymer microspheres bearing PEG brushes of different molecular weights (Mn = 2000 and 5000) via our previously developed reversible addition-fragmentation chain transfer (RAFT) coupling chemistry, their supramolecular inclusion complexation with α-CD, and subsequent chemical crosslinking. The chain length of the surface-grafted PEG brushes showed much influence on the water-compatibility of MIPs. Whereas the MIP particles bearing PEG brushes of Mn = 2000 hardly showed specific template bindings in both pure water and pure milk, those bearing PEG brushes of Mn = 5000 exhibited moderate specific template bindings in pure water. Nevertheless, the latter MIP particles still failed to show enough specific template bindings in pure milk. The inclusion of α-CD onto PEG brushes proved to largely enhance the surface hydrophilicity of MIPs and lead to their much improved water-compatibility. In particular, the MIP microspheres bearing α-CD-modified PEG brushes of Mn = 5000 showed excellent specific template bindings in both pure water and pure milk. The above strategy not only paves the way for efficiently preparing biological sample-compatible MIPs, but also opens the possibility of generating many other advanced biomaterials with high antifouling properties.

Controlled Self-Assembly of Photofunctional Supramolecular Nanotubes.

Designing supramolecular nanotubes (SNTs) with distinct dimensions and properties is highly desirable, yet challenging, since structural control strategies are lacking. Furthermore, relatively complex building blocks are often employed in SNT self-assembly. Here, we demonstrate that symmetric bolaamphiphiles having a hydrophobic core comprised of two perylene diimide moieties connected via a bipyridine linker and bearing polyethylene glycol (PEG) side chains can self-assemble into diverse molecular nanotubes. The structure of the nanotubes can be controlled by assembly conditions (solvent composition and temperature) and a PEG chain length. The resulting nanotubes differ both in diameter and cross section geometry, having widths of 3 nm (triangular-like cross-section), 4 nm (rectangular), and 5 nm (hexagonal). Molecular dynamics simulations provide insights into the stability of the tubular superstructures and their initial stages of self-assembly, revealing a key role of oligomerization via side-by-side aromatic interactions between bis-aromatic cores. Probing electronic and photonic properties of the nanotubes revealed extended electron delocalization and photoinduced charge separation that proceeds via symmetry breaking, a photofunction distinctly different from that of the fibers assembled from the same molecules. A high degree of structural control and insights into SNT self-assembly advance design approaches toward functional organic nanomaterials.

Resveratrol derivatives as a pharmacological tool.

Prodrugs of resveratrol are under development. Among the long-term goals, still largely elusive, are (1) modulating physical properties (e.g., water-soluble derivatives bearing polyethylene glycol chains), (2) changing distribution in the body (e.g., galactosyl derivatives restricted to the intestinal lumen), (3) increasing absorption from the gastrointestinal tract (e.g., derivatives imitating the natural substrates of endogenous transporters), and (4) hindering phase II metabolism (e.g., temporarily blocking the hydroxyls), all contributing to (5) increasing bioavailability. The chemical bonds that have been tested for functionalization include carboxyester, acetal, and carbamate groups. A second approach, which can be combined with the first, seeks to reinforce or modify the biochemical activities of resveratrol by concentrating the compound at specific subcellular sites. An example is provided by mitochondria-targeted derivatives. These proved to be pro-oxidant and cytotoxic in vitro, selectively killing fast-growing and tumor cells when supplied in the low micromolar range. This suggests the possibility of anticancer applications.

A transparent, hazy, and strong macroscopic ribbon of oriented cellulose nanofibrils bearing poly(ethylene glycol).

A macroscopic ribbon of oriented cellulose nanofibrils bearing polyethylene glycol is fabricated by stretching the cellulose nanofibrils network structure in the hydrogel state. The covalently grafted polyethylene glycol on the nanofibril surface facilitates the alignment and compartmentalization of individual nanofibrils in the ribbon. The ribbon has ultrahigh tensile strength (576 ± 54 MPa), modulus (32.3 ± 5.7 GPa), high transparency, and haze.

Photopolymerized micelles of diacetylene amphiphile: physical characterization and cell delivery properties.

A series of polydiacetylene (PDA) - based micelles were prepared from diacetylenic surfactant bearing polyethylene glycol, by increasing UV-irradiation times. These polymeric lipid micelles were analyzed by physicochemical methods, electron microscopy and NMR analysis. Cellular delivery of fluorescent dye suggests that adjusting the polymerization state is vital to reach the full in vitro potential of PDA-based delivery systems.

Fluorinated derivatives of a polyaspartamide bearing polyethylene glycol chains as oxygen carriers

In this paper the synthesis and characterization of new fluorinated polymers based on a polyaspartamide bearing polyethylene glycol (PEG) chains, are reported. The starting material was the α,β-poly( N-2-hydroxyethyl)- dl-aspartamide (PHEA), a water soluble and biocompatible polymer, that has been derivatized with both polyethylene glycol (with a molecular weight of 2000 Da) and 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole. By varying the amount of the fluorinated oxadiazole, three samples have been prepared and characterized by FT-IR, 1H NMR, 19F NMR and UV–VIS spectroscopy. Size exclusion chromatography analysis of these copolymers revealed the occurrence of a self-association process in aqueous medium. The value of critical aggregation concentration has been evaluated by performing a tensiometric study, whereas the size of these aggregates has been determined by photon correlation spectroscopy. Oxygen solubility studies in aqueous solutions of these fluoropolymers showed their ability to maintain high oxygen levels in solution. The biocompatibility of these fluoropolymers has been evaluated by performing an in vitro viability assay on human chronic myelogenous leukaemia cells (K-562), chosen as a model cell line, and haemolysis experiments on human red blood cells. All these properties suggest the potential use of these fluoropolymers as artificial oxygen carriers.

Stable Aromatic Dianion in Water

Perylene diimide (PDI) bearing polyethylene glycol substituents at the imide positions was reduced in water with sodium dithionite to produce an aromatic dianion. The latter is stable for months in deoxygenated aqueous solutions, in contrast to all known aromatic dianions which readily react with water. Such stability is due to extensive electron delocalization and the aromatic character of the dianion, as evidenced by spectroscopic and theoretical studies. The dianion reacts with oxygen to restore the parent neutral compound, which can be reduced again in an inert atmosphere with sodium dithionite to give the dianion. Such reversible charging renders PDIs useful for controlled electron storage and release in aqueous media. Simple preparation of the dianion, reversible charging, high photoredox power, and stability in water can lead to development of new photofunctional and electron transfer systems in the aqueous phase.