Search results for "polymers"
showing 10 items of 3567 documents
Amphiphilic Copolymers Based on Poly[(hydroxyethyl)-d,l-aspartamide]: A Suitable Functional Coating for Biocompatible Gold Nanostars
2013
Novel amphiphilic copolymers have been synthesized based on a biocompatible poly(hydroxyethylaspartamide) (PHEA) backbone, bearing both anchoring groups for gold nanoparticles, such as thiols and disulfide, and conjugable moieties, such as amino groups, the latter as points suitable for appending further functional agents. The strategy was to functionalize α,β-poly[(N-2- hydroxyethyl)-d,l-aspartamide] (PHEA) with PEG2000-NH2 and with ethylenediamine (EDA) obtaining a partially pegylated copolymer with a large number of pendant primary amino groups. A fraction of the latter was conjugated with molecules bearing terminal thiol moieties such as 12-mercaptododecanoic acid (MDA) and disulfide gr…
Polypeptoid-block-polypeptide Copolymers: Synthesis, Characterization, and Application of Amphiphilic Block Copolypept(o)ides in Drug Formulations an…
2013
We report the synthesis of polysarcosine-block-polyglutamic acid benzylester (PSar-block-PGlu(OBn)) and polysarcosine-block-polylysine-ε-N-benzyloxycarbonyl (PSar-block-PLys(Z)) copolymers. The novel polypeptoid-block-polypeptide copolymers (Copolypept(o)ides) have been synthesized by ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs). Polymerization conditions were optimized regarding protecting groups, block sequence and length. While the degree of polymerization of the PSar block length was set to be around 200 or 400, PGlu(OBn) and PLys(Z) block lengths were varied between 20 to 75. The obtained block copolymers had a total degree of polymerization of 220-475 and dispersity…
Size- and coating-dependent uptake of polymer-coated gold nanoparticles in primary human dermal microvascular endothelial cells.
2012
A library-orientated approach is used to gain understanding of the interactions of well-defined nanoparticles with primary human endothelial cells, which are a key component of the vasculature. Fifteen sequentially modified gold nanoparticles (AuNPs) based on three different core sizes (18, 35, 65 nm) and five polymeric coatings were prepared. The synthetic methodology ensured homogeneity across each series of particles to allow sequential investigation of the chemical features on cellular interactions. The toxicity of these nanoparticles, their uptake behavior in primary human dermal microvascular endothelial cells (HDMECs), and quantification of uptake were all investigated. The results o…
Supramolecular Assemblies Based on Complexes of Nonionic Amphiphilic Cyclodextrins and a meso-Tetra(4- sulfonatophenyl)porphine Tributyltin(IV) Deriv…
2013
Amphiphilic cyclodextrin (ACyD) provides water-soluble and adaptable nanovectors by modulating the balance between the hydrophobic and hydrophilic chains at both CyD sides. This work aimed to design nanoassemblies based on nonionic and hydrophilic ACyD (SC6OH) for the delivery of a poor-water-soluble organotin(IV)-porphyrin derivative [(Bu3Sn)4TPPS] to melanoma cancer cells. To characterize the porphyrin derivatives under simulated physiological conditions, a speciation was performed using complementary techniques. In aqueous solution (≤ 20 μM), (Bu3Sn)4TPPS primarily exists as a monomer (2 in Figure 1), as suggested by the low static anisotropy (ρ ≈ 0.02) with a negligible formation of por…
α-Mannosyl-Functionalized Cationic Nanohydrogel Particles for Targeted Gene Knockdown in Immunosuppressive Macrophages
2019
Immunosuppressive M2 macrophages govern the immunophathogenic micromilieu in many severe diseases including cancer or fibrosis, thus, their re-polarization through RNA interference is a promising concept to support combinatorial therapies. For targeted siRNA delivery, however, safe and stable carriers are required that manage cell specific transport to M2 macrophages. Here, siRNA-loaded cationic nanogels are reported with α-mannosyl decorated surfaces that target and modify M2 macrophages selectively. Via amphiphilic precursor block copolymers bearing one single α-mannosyl moiety at their chain end mannosylated cationic nanohydrogel particles (ManNP) were obtained of 20 nm diameter determin…
Effect of Core-Crosslinking on Protein Corona Formation on Polymeric Micelles.
2021
Most nanomaterials acquire a protein corona upon contact with biological fluids. The magnitude of this effect is strongly dependent both on surface and structure of the nanoparticle. To define the contribution of the internal nanoparticle structure, protein corona formation of block copolymer micelles with poly(N-2-hydroxypropylmethacrylamide) (pHPMA) as hydrophilic shell, which are crosslinked-or not-in the hydrophobic core is comparatively analyzed. Both types of micelles are incubated with human blood plasma and separated by asymmetrical flow field-flow fractionation (AF4). Their size is determined by dynamic light scattering and proteins within the micellar fraction are characterized by…
Physico-chemical characterization of polyethylenes obtained in the presence of different catalysts containing alkoxyligands
1986
The effect of the kind and number of alkoxy ligands (OR) in organometallic Ti-Al catalyst on the properties of polyethylenes obtained i.e. molecular weight, mechanical and rheological properties, density, crystallinity, melting point, heat of fusion and number of chain branches was studied. Polyethylene obtained over Ti-Al catalyst with OR ligands has particularly high molecular weight, high density, better mechanical properties, higher resistance to heat, different rheological characteristics and lower number ot chain branches in comparison with standard HDPE. It is possible to control the polyethylene synthesis process and to obtain the polymer of required properties by selecting the OR …
Operational Procedures in the Theory of the Drug Release from Chitosan Hydrogels
2018
We build a theoretical model based on a generalization of harmonic applications of Misner-type. It results a sine-Gordon type fractal differential equation whose elliptical solutions can describe, through a convenient choice of fractal dynamic constants, various modes of drug release. Thus, the entire class of empirical models (Higuchi, Korsmeyer-Peppas, Peppas-Sahlin) describing the drug release processes can be dispensed with.
Thermal stability of poly(styrene-b-methyl methacrylate) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate)
1993
The thermal stability of poly(styrene-b-methyl methacrylate) diblock copolymers (= P(S-b-MMA)) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate) triblock copolymers (=P(S-b-EB-b-MMA)) was investigated. Well-defined high molecular weight block copolymers with narrow molecular weight distribution (MWD) were molded at different temperatures in vacuum and the alteration of the MWD was sensitively monitored by gel permeation chromatography (GPC). Up to 240°C P(S-b-MMA) shows almost no broadening of the MWD. At higher temperatures low molecular weight polystyrene-rich portions are formed. The number average molecular weight (Mn) is strongly reduced. P(S-b-EB-b-MMA) triblock copolymer…
Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface
2008
Calamitic (rod-shaped) and discotic (disc-shaped) thermotropic liquid crystalline (LC) compounds were spread at the air-water interface, and their ability to form monolayers was studied. The calamitic LCs investigated were found to form monolayers which behave analogously to conventional amphiphiles such as fatty acids. The spreading of the discotic LCs produced monolayers as well, but with a behaviour different from classical amphiphiles. The areas occupied per molecule are too small to allow the contact of all hydrophilic groups with the water surface and the packing of all hydrophobic chains. Various molecular arrangements of the discotics at the water surface to fit the spreading data a…