Search results for "PLASTICS"
showing 10 items of 2724 documents
Liquid-Crystalline Colloidal Particles
2004
Here we report about the synthesis of colloidal particles of nematic and smectic liquid-crystalline polymers. For this purpose mesogen-containing acrylate monomers were synthesized and polymerized in a special modification of a precipitation polymerization called dispection polymerization. By variation of the polymerization conditions colloidal particles of different size and polydispersity could be obtained including very narrowly distributed samples in optimized batches. On azobenzene-containing colloidal particles switching experiments with polarized light were performed. It could be observed that the nematic director of the mesogens within the colloidal particles can be rotated due to t…
Polymerization of methyl methacrylate through ionizing radiation in CO2-based dense systems
2000
Herein, we report the use of ionizing radiation to induce a dispersion polymerization reaction in dense CO2. As a model system, the polymerization of methyl methacrylate in the presence of poly(dimethylsiloxane) stabilizers was investigated. It was demonstrated that the dose plays the key role in the progress of the reaction and in the morphology of the resulting polymer. Dispersion polymerization carried out in the presence of mono- and bifunctionalized surfactants gave differently structured polymers. The polymers obtained have been characterized by scanning electron microscopy, solubility tests, and gel permeation chromatography, and the molecular structure has been related to dynamic me…
Synthesis of Liquid-Crystalline Colloids in Nonpolar Media and their Manipulation in Electric Fields
2009
The first synthesis of anisotropic liquid-crystalline colloids in silicone oil by a direct (radical) polymerization of a monomer in THF/silicone oil mixtures with the help of siloxane containing stabilizers is described. The size of the colloids is in the lower μm range and can be adjusted by varying the mixture. The resulting colloids show a bipolar director configuration if they are small (<1.5 μm) and a radial configuration if they are larger. The colloids are sterically stabilized, and, due to the nonpolarity of the solvent, the disturbing effects of migrating ions are excluded and experiments in the electric field can be conducted. Both line formation in DC fields and a periodic switch…
Studies of monolayer/substrate adhesion as function of the monolayer headgroup charge: DMPE and DMPA
1991
The variation of the work of adhesion between lipid monolayers and a plane silicon oxide surface in a typical LB-configuration is measured as function of the subphase pH. The adhesion energy is deduced via fluorescence microscopy from the equilibrium meniscus height. With increasing pH the negative headgroup charge of both, dimyristoylphosphatidylethanolamine (DMPE) and dimyristoylphosphatidic acid (DMPA) monolayers increases. The increasing charge of DMPE is reflected in a measured decrease of the work of adhesion at higher pH. The DMPA/SiO2 interaction is not affected by increasing headgroup charges. These results are qualitatively understood in terms of an electrostatic double layer inte…
From In Silico to Experimental Validation: Tailoring Peptide Substrates for a Serine Protease.
2020
Smart nanocarriers for the transport of drugs to tumor cells are nowadays of great interest for treating cancer. The use of enzymatic stimuli to cleave peptide-based drug nanocapsules for the selective release of nanocapsule cargo in close proximity to tumor cells opens new possibilities in cancer research. In the present work, we demonstrate a methodology for finding and optimizing cleavable substrate sequences by the type II transmembrane serine protease hepsin, which is highly overexpressed in prostate cancer. The design and screening of combinatorial libraries in silico against the binding cavity of hepsin allow the identification of a panel of promising substrates with high-calculated …
In VitroRelease of Local Anaesthetic and Anti-Inflammatory Drugs from Crosslinked Collagen Based Device
2012
The drug delivery systems that are the object of this article take the form of a hydrophilic matrix (collagen or crosslinked collagen) containing a drug. These devices can be used as The model active agents, were chosen from the range of local anaesthetics (lidocaine hydrochloride), anti-inflammatory (diclofenac sodium salt) and antioxydant (caffeic acid). Whatever the drug affinity for water, in the first time of the experiments, the release appears to be systematically delayed when the matrix is crosslinked. For lidocaine hydrochloride based systems, as the amount of drug increases in the matrix, the high gap concentration between the matrix and the buffer solution promote the diffusion a…
Functionalized Poly(N-isopropylacrylamide)-Based Microgels in Tumor Targeting and Drug Delivery
2021
Over the past several decades, the development of engineered small particles as targeted and drug delivery systems (TDDS) has received great attention thanks to the possibility to overcome the limitations of classical cancer chemotherapy, including targeting incapability, nonspecific action and, consequently, systemic toxicity. Thus, this research aims at using a novel design of Poly(N-isopropylacrylamide) p(NIPAM)-based microgels to specifically target cancer cells and avoid the healthy ones, which is expected to decrease or eliminate the side effects of chemotherapeutic drugs. Smart NIPAM-based microgels were functionalized with acrylic acid and coupled to folic acid (FA), targeting the f…
Amphiphilic Copolymers Shuttle Drugs Across the Blood-Brain Barrier.
2015
Medical treatment of diseases of the central nervous system requires transport of drugs across the blood-brain barrier (BBB). Here, it is extended previously in vitro experiments with a model compound to show that the non-water-soluble and brain-impermeable drug domperidone (DOM) itself can be enriched in the brain by use of an amphiphilic copolymer as a carrier. This carrier consists of poly(N-(2-hydroxypropyl)-methacrylamide), statistically copolymerized with 10 mol% hydrophobic lauryl methacrylate, into whose micellar aggregates DOM is noncovalently absorbed. As tested in a BBB model efficient transport of DOM across, the BBB is achievable over a wide range of formulations, containing 0.…
In vitro study of N-succinyl chitosan for targeted delivery of 5-aminosalicylic acid to colon
2011
In vitro study on N-succinyl chitosan and chitosan (control) matrices for selective colon delivery of 5-aminosalicylic acid is described. Matrices containing β-cyclodextrin were also prepared. As shown by DSC analyses, the drug was successfully loaded into the matrices reaching up to 95% entrapment efficiency. Swelling and drug release were studied at pH 1.2, pH 7.4, and in a pH gradient medium to simulate the gastro-intestinal transit. Main result of this study was a higher capability of N-succinyl chitosan alone to better control drug release in the simulated gastro-intestinal transit: N-succinyl chitosan gave the lowest release in acid medium (≅15%) and the highest in alkaline environmen…
Injectable in situ forming microgels of hyaluronic acid-g-polylactic acid for methylprednisolone release
2013
Abstract A hydrophobic derivative of hyaluronic acid (HA), obtained by grafting polylactic acid (PLA) to the polysaccharide, has been exploited to produce injectable in situ forming microgels. First of all, self assembling properties of HA-g-PLA copolymer have been evaluated by determining the critical aggregation concentration (CAC) value, then this copolymer has been dissolved in a mixture water/NMP 5:2 v/v with a concentration greater than CAC. When solutions at 1% or 2% w/v were injected into Dulbecco phosphate buffer solution (DPBS) pH 7.4, microgels promptly are formed. Their stability in DPBS pH 7.4 in the absence or in the presence of hyaluronidase and cell compatibility have been e…