Search results for "Reversible"

HPMA copolymers as surfactants in the preparation of biocompatible nanoparticles for biomedical application.

2012

In this work we describe the application of amphiphilic N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymers as polymeric surfactants in miniemulsion techniques. HPMA-based copolymers with different ratios of HPMA (hydrophilic) to laurylmethacrylate (LMA; hydrophobic) units were synthesized by RAFT polymerization and postpolymerization modification. The amphiphilic polymers can act as detergents in both the miniemulsion polymerization of styrene and the miniemulsion process in combination with solvent evaporation, which was applied to polystyrene and polylactide. Under optimized conditions, monodisperse colloids can be prepared. The most promising results could be obtained by using the…

Peculiar behavior of degenerative chain transfer polymerization of a phosphonated methacrylate

2009

Living/controlled radical polymerization of dimethyl(methacryloyloxy)methyl phosphonate (MAPC) has been attempted using degenerative transfer to produce block copolymers. RAFT polymerization of this monomer is sensitive to very low level of oxygen and in any case limited to low monomer conversion. Reverse iodine transfer polymerization (RITP) leads to higher monomer conversion with a limited amount of living polymer (55% by H NMR), precluding an efficient synthesis of block copolymers. A PMMA-b-PMAPC diblock copolymer was therefore synthesized by iodine transfer polymerization (ITP) of MAPC from a PMMA-Imacro-chain transfer agent prepared by RITP. The diblock copolymer, purified by selectiv…

2018

The design of multifunctional polymer-based vectors, forming pDNA vaccines, offers great potential in cancer immune therapy. The transfection of dendritic immune cells (DCs) with tumour antigen-encoding pDNA leads to an activation of the immune system to combat tumour cells. In this work, we investigated the chemical attachment of DEC205 antibodies (aDEC205) as DC-targeting structures to polyplexes of P(Lys)-b-P(HPMA). The conjugation of a synthetic block copolymer and a biomacromolecule with various functionalities (aDEC205) requires bioorthogonal techniques to avoid side reactions. Click chemistry and in particular the strain-promoted alkyne-azide cycloaddition (SPAAC) can provide the req…

Squaric Ester-Based, pH-Degradable Nanogels: Modular Nanocarriers for Safe, Systemic Administration of Toll-like Receptor 7/8 Agonistic Immune Modula…

2021

Small-molecular Toll-like receptor 7/8 (TLR7/8) agonists hold promise as immune modulators for a variety of immune therapeutic purposes including cancer therapy or vaccination. However, due to their rapid systemic distribution causing difficult-to-control inflammatory off-target effects, their application is still problematic, in particular systemically. To address this problem, we designed and robustly fabricated pH-responsive nanogels serving as versatile immunodrug nanocarriers for safe delivery of TLR7/8-stimulating imidazoquinolines after intravenous administration. To this aim, a primary amine-reactive methacrylamide monomer bearing a pendant squaric ester amide is introduced, which i…

Pentafluorophenyl Ester-based Polymersomes as Nanosized Drug-Delivery Vehicles

2015

In this work, activated ester chemistry is employed to synthesize biocompatible and readily functionalizable polymersomes. Via aminolysis of pentafluorophenyl methacrylate-based precursor polymers, an N-(2-hydroxypropyl) methacrylamide (HPMA)-analog hydrophilic block is obtained. The precursor polymers can be versatile functionalized by simple addition of suitable primary amines during aminolysis as demonstrated using a fluorescent dye. Vesicle formation is proven by cryoTEM and light scattering. High encapsulation efficiencies for hydrophilic cargo like siRNA are achieved using dual centrifugation and safe encapsulation is demonstrated by gel electrophoresis. In vitro studies reveal low cy…

Identification of Plakortide E from the Caribbean Sponge Plakortis halichondroides as a Trypanocidal Protease Inhibitor using Bioactivity-Guided Frac…

2014

In this paper, we report new protease inhibitory activity of plakortide E towards cathepsins and cathepsin-like parasitic proteases. We further report on its anti-parasitic activity against Trypanosoma brucei with an IC50 value of 5 mu M and without cytotoxic effects against J774.1 macrophages at 100 mu M concentration. Plakortide E was isolated from the sponge Plakortis halichondroides using enzyme assay-guided fractionation and identified by NMR spectroscopy and mass spectrometry. Furthermore, enzyme kinetic studies confirmed plakortide E as a non-competitive, slowly-binding, reversible inhibitor of rhodesain.

The cyclicity of the elliptic segment loops of the reversible quadratic Hamiltonian systems under quadratic perturbations

2004

Abstract Denote by Q H and Q R the Hamiltonian class and reversible class of quadratic integrable systems. There are several topological types for systems belong to Q H ∩ Q R . One of them is the case that the corresponding system has two heteroclinic loops, sharing one saddle-connection, which is a line segment, and the other part of the loops is an ellipse. In this paper we prove that the maximal number of limit cycles, which bifurcate from the loops with respect to quadratic perturbations in a conic neighborhood of the direction transversal to reversible systems (called in reversible direction), is two. We also give the corresponding bifurcation diagram.

Reversible inhibition of C1Q release from guinea pig macrophages by 2,2'-dipyridyl: Evidence for a posttranslational hydroxylation step in the biosyn…

1978

Novel high-performance QCA Fredkin gate and designing scalable QCA binary to gray and vice versa

2022

AbstractIn the design of digital logic circuits, QCA technology is an excellent alternative to CMOS technology. Its advantages over CMOS include low power consumption, fast circuit switching, and nanoscale design. Circuits that convert data between different formats are code converters. Code converters have an essential role in high-performance computing and signal processing. In this paper, first, we proposed a novel QCA structure for the quantum reversible Fredkin gate. Second, we proposed 4-bit and 8-bit QCA binary-to-gray converter and vice versa. For the second proposal, both reversible and irreversible structures are suggested. The proposed structures are scalable up to N bits. To cha…

Reversible Dimerization and Polymerization of a Janus Diradical To Produce Labile C−C Bonds and Large Chromic Effects

2016

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ‐dimers and σ‐polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C−C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain …