Search results for "PEG ratio"

Silver Oxide Mediated Monotosylation of Poly(ethylene glycol) (PEG): Heterobifunctional PEG via Polymer Desymmetrization

2017

Heterobifunctional poly(ethylene glycol)s (PEGs) are key structures for bioconjugation in the context of the “PEGylation” strategy to enhance blood circulation times of, for example, peptide drugs or “stealth” liposomes. The formation of heterobifunctional PEGs from symmetric PEG diols is challenging because of limited yields of the targeted monofunctional product and difficulties associated with separation steps. On the basis of a detailed comparison of reaction conditions, we have investigated a “polymer desymmetrization” strategy to maximize the yields of monofunctional PEG tosylate. The tosylation reaction in the presence of the heterogeneous catalyst silver oxide and potassium iodide i…

Influence of Surface Charge and Polymer Coating on Internalization and Biodistribution of Polyethylene Glycol-Modified Iron Oxide Nanoparticles

2015

International audience; The aim of this study was to investigate the influence of the surface charge and coating of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) on their in vitro and in vivo behaviors. Neutral and negatively-charged PEG-based SPIONs were synthesized and compared to Resovist (R), a carboxydextran-based SPION currently used in clinics. Their cytotoxicity, cell internalization, and potential as contrast agents for magnetic resonance imaging were assessed. Neutral pegylated SPIONs were internalized less readily by the reticuloendothelial system and showed a lower uptake by the liver, compared to negatively-charged SPIONs (with carboxydextran and PEG). These results sugge…

Efficient Shielding of Polyplexes Using Heterotelechelic Polysarcosines

2018

Shielding agents are commonly used to shield polyelectrolyte complexes, e.g. polyplexes, from agglomeration, precipitation in complex media, like blood, and thus enhance their circulation times in vivo. Since up to now primarily poly(ethylene glycol) (PEG) has been investigated to shield non-viral carriers for systemic delivery, we report on the use of polysarcosine (pSar) as a potential alternative for steric stabilization. A redox-sensitive, cationizable lipo-oligomer structure (containing two cholanic acids attached via a bioreducible disulfide linker to an oligoaminoamide backbone in T-shape configuration) was equipped with azide-functionality by solid phase supported synthesis. After m…

Granulocyte Colony-Stimulating Factor Nanocarriers for Stimulation of the Immune System (Part I): Synthesis and Biodistribution Studies

2018

In the field of cancer immunotherapy, an original approach consists of using granulocyte colony-stimulating factor (G-CSF) to target and activate neutrophils, cells of the innate immune system. G-CSF is a leukocyte stimulating molecule which is commonly used in cancer patients to prevent or reduce neutropenia. We focused herein on developing a G-CSF nanocarrier which could increase the in vivo circulation time of this cytokine, keeping it active for targeting the spleen, an important reservoir of neutrophils. G-CSF-functionalized silica and gold nanoparticles were developed. Silica nanoparticles of 50 nm diameter were functionalized by a solid phase synthesis approach. The technology enable…

Relationship between conformation and physicochemical properties of polypeptides. II. GPC as a tool for the detection of conformational transitions o…

1983

Tailoring Novel PTFE Surface Properties: Promoting Cell Adhesion and Antifouling Properties via a Wet Chemical Approach

2016

Many biomaterials used for tissue engineering applications lack cell-adhesiveness and, in addition, are prone to nonspecific adsorption of proteins. This is especially important for blood-contacting devices such as vascular grafts and valves where appropriate surface properties should inhibit the initial attachment of platelets and promote endothelial cell colonization. As a consequence, the long-term outcome of the implants would be improved and the need for anticoagulation therapy could be reduced or even abolished. Polytetrafluoroethylene (PTFE), a frequently used polymer for various medical applications, was wet-chemically activated and subsequently modified by grafting the endothelial …

Surface Modification of Polysaccharide-Based Nanoparticles with PEG and Dextran and the Effects on Immune Cell Binding and Stimulatory Characteristic…

2017

Surface modifications of nanoparticles can alter their physical and biological properties significantly. They effect particle aggregation, circulation times, and cellular uptake. This is particularly critical for the interaction with primary immune cells due to their important role in particle processing. We can show that the introduction of a hydrophilic PEG layer on the surface of the polysaccharide-based nanoparticles prevents unwanted aggregation under physiological conditions and decreases unspecific cell uptake in different primary immune cell types. The opposite effect can be observed with a parallel-performed introduction of a layer of low molecular weight dextran (3.5 and 5 kDa) on…

Keyhole limpet hemocyanin (KLH), I: Reassociation from Immucothel® followed by separation of KLH1 and KLH2

1997

Abstract Studies of keyhole limpet hemocyanin (KLH) normally require purification of functional complexes directly from living animals. An alternative procedure is described wherein a commercial preparation of KLH which is fully dissociated into its subunits (Immucothel®, biosyn Arzneimittel GmbH) is reassociated in the presence of a high concentration of calcium and magnesium. The reassociation products, when observed by electron microscopy, consist of didecamers, multidecamers and flexible tubules of varying length. The two forms of KLH described previously and designated KLH1 and KLH2, are present in the reassocated mixture as homo-oligomers/polymers and can be separated by selective dis…

Fabrication of quercetin and curcumin bionanovesicles for the prevention and rapid regeneration of full-thickness skin defects on mice

2013

In the present work biocompatible quercetin and curcumin nanovesicles were developed as a novel approach to prevent and restore skin tissue defects on chronic cutaneous pathologies. Stable and suitable quercetin- and curcumin-loaded phospholipid vesicles, namely liposomes and penetration enhancer-containing vesicles (PEVs), were prepared. Vesicles were made from a highly biocompatible mixture of phospholipids and alternatively a natural polyphenol, quercetin or curcumin. Liposomes were obtained by adding water, while PEVs by adding polyethylene glycol 400 and Oramix®CG110 to the water phase. Transmission electron microscopy, cryogenic-transmission electron microscopy and small- and wide-ang…

Acquisition of Structure-guiding and Structure-forming Properties during Maturation from the Pro-silicatein to the Silicatein Form

2012

Silicateins are the key enzymes involved in the enzymatic polycondensation of the inorganic scaffold of the skeletal elements of the siliceous sponges, the spicules. The gene encoding pro-silicatein is inserted into the pCold TF vector, comprising the gene for the bacterial trigger factor. This hybrid gene is expressed in Escherichia coli and the synthesized fusion protein is purified. The fusion protein is split into the single proteins with thrombin by cleavage of the linker sequence present between the two proteins. At 23 °C, the 87 kDa trigger factor-pro-silicatein fusion protein is cleaved to the 51 kDa trigger factor and the 35 kDa pro-silicatein. The cleavage process proceeds and res…