Search results for "nanoparticle"
showing 10 items of 2198 documents
Evaluation of polyalkylcyanoacrylate nanoparticles as a potential drug carrier: preparation, morphological characterization and loading capacity.
1993
Some physicochemical behaviours were investigated of polyethyl- (PECA) and polyisobutylcyanoacrylate (PICA), which, in recent years, have been proposed as nanoparticle colloidal systems for drug carrying. We observed the influence of preparation conditions, such as pH value and surfactant concentration, on parameters such as particle size and polymer molecular weight. Lower operating pH values (0-2) resulted in smaller nanoparticles than those prepared at pH 5.5. The polymer molecular weight was also a function of pH: low molecular weight at low pH and vice-versa. The surfactant concentration positively influenced main particle size and polymer molecular weight. These trends were independen…
Spherical polymer brushes under good solvent conditions: molecular dynamics results compared to density functional theory.
2010
A coarse grained model for flexible polymers end-grafted to repulsive spherical nanoparticles is studied for various chain lengths and grafting densities under good solvent conditions, by Molecular Dynamics methods and density functional theory. With increasing chain length the monomer density profile exhibits a crossover to the star polymer limit. The distribution of polymer ends and the linear dimensions of individual polymer chains are obtained, while the inhomogeneous stretching of the chains is characterized by the local persistence lengths. The results on the structure factor of both single chain and full spherical brush as well as the range of applicability of the different theoretic…
HPMA-based block copolymers promote differential drug delivery kinetics for hydrophobic and amphiphilic molecules.
2015
Abstract We describe a method how polymeric nanoparticles stabilized with (2-hydroxypropyl)methacrylamide (HPMA)-based block copolymers are used as drug delivery systems for a fast release of hydrophobic and a controlled release of an amphiphilic molecule. The versatile method of the miniemulsion solvent-evaporation technique was used to prepare polystyrene (PS) as well as poly-d/l-lactide (PDLLA) nanoparticles. Covalently bound or physically adsorbed fluorescent dyes labeled the particles’ core and their block copolymer corona. Confocal laser scanning microscopy (CLSM) in combination with flow cytometry measurements were applied to demonstrate the burst release of a fluorescent hydrophobic…
Electrochemical Characterization of Polyelectrolyte/Gold Nanoparticle Multilayers Self-Assembled on Gold Electrodes
2006
Polyelectrolyte/gold nanoparticle multilayers composed of poly(l-lysine) (pLys) and mercaptosuccinic acid (MSA) stabilized gold nanoparticles (Au NPs) were built up using the electrostatic layer-by-layer self-assembly technique upon a gold electrode modified with a first layer of MSA. The assemblies were characterized using UV-vis absorption spectroscopy, cyclic and square-wave voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. Charge transport through the multilayer was studied experimentally as well as theoretically by using two different redox pairs [Fe(CN)(6)](3-/4-) and [Ru(NH(3))(6)](3+/2+). This paper reports a large sensitivity to the charge of the out…
Targeting cells of the immune system: mannosylated HPMA–LMA block-copolymer micelles for targeting of dendritic cells
2016
Background: Successful tumor immunotherapy depends on the induction of strong and sustained tumor antigen-specific immune responses by activated antigen-presenting cells (APCs) such as dendritic cells (DCs). Since nanoparticles have the potential to codeliver tumor-specific antigen and DC-stimulating adjuvant in a DC-targeting manner, we wanted to assess the suitability of mannosylated HPMA-LMA block polymers for immunotherapy. Materials & methods: Fluorescence-labeled block copolymer micelles derived from P(HPMA)-block-P(LMA) copolymers and according statistical copolymers were synthesized via RAFT polymerization, and loaded with the APC activator L18-MDP. Both types of copolymers wer…
Micro- to Nanoscale Bio-Hybrid Hydrogels Engineered by Ionizing Radiation
2021
Bio-hybrid hydrogels consist of a water-swollen hydrophilic polymer network encapsulating or conjugating single biomolecules, or larger and more complex biological constructs like whole cells. By modulating at least one dimension of the hydrogel system at the micro- or nanoscale, the activity of the biological component can be extremely upgraded with clear advantages for the development of therapeutic or diagnostic micro- and nano-devices. Gamma or e-beam irradiation of polymers allow a good control of the chemistry at the micro-/nanoscale with minimal recourse to toxic reactants and solvents. Another potential advantage is to obtain simultaneous sterilization when the absorbed doses are wi…
Influence of Temperature on Calcium Hydroxyapatite Nanopowders
2012
The aim of this work is to investigate the effects of thermal treatment, in the range of temperature between 80°C - 900°C, on crystallinity, morphology and particles size of calcium hydroxylapatite nanopowders (HAp). A complete study was carried out applying 31P Magic Angle Spinning NMR, X-ray diffraction, nitrogen porosimetry and Transmis- sion Electron Microscopy techniques. HAp specimens were prepared by chemical precipitation in an aqueous solution of calcium nitrate and ammonium hydrogen phosphate. The thermal treatment performed, showed the formation of crystals whose appearance has three main morphologies and different particles size. HAp treated up to 500°C showed a set of needle-li…
Calcium Sulfate Nanoparticles with Unusual Dispersibility in Organic Solvents for Transparent Film Processing
2018
Calcium sulfate is one of the most important construction materials. Today it is employed as high-performance compound in medical applications and cement mixtures. We report a synthesis for calcium sulfate nanoparticles with outstanding dispersibility properties in organic solvents without further functionalization. The nanoparticles (amorphous with small γ-anhydrite crystallites, 5–50 nm particle size) form long-term stable dispersions in acetone without any sign of precipitation. 1H NMR spectroscopic techniques and Fourier-transform infrared spectroscopy (FTIR) reveal absorbed 2-propanol on the particle surfaces that induce the unusual dispersibility. Adding water to the nanoparticle disp…
Chromium oxide nanoparticles with controlled size prepared from hydrothermal chromium oxyhydroxide precursors
2017
Abstract This work reports the preparation of morphologically well-defined chromium oxide nanoparticles with controlled sizes of 20–30 nm. The synthetic procedure encompass two stages, the first one refers to the preparation of chromium oxyhydroxide nanoparticles by a hydrothermal approach of previously precipitated xerogels, followed by a thermal transformation of CrOOH nanoparticles to Cr2O3. The series of chromium oxyhydroxide particles sized over the range 15–50 nm were prepared through the control of the pH of precipitation of the xerogels and the water/xerogel ratio of the hydrothermal aging. Results showed the formation of non-aggregated oxyhydroxide nanoparticles with two different …
Highly soluble multifunctional MnO nanoparticles for simultaneous optical and MRI imaging and cancer treatment using photodynamic therapy
2010
Superparamagnetic MnO nanoparticles were functionalized using a hydrophilic ligand containing protoporphyrin IX as photosensitizer. By virtue of their magnetic properties these nanoparticles may serve as contrast enhancing agents for magnetic resonance imaging (MRI), while the fluorescent target ligand protoporphyrin IX allows simultaneous tumor detection and treatment by photodynamic therapy (PDT). Caki-1 cells were incubated with these nanoparticles. Subsequent exposure to UV light lead to cell apoptosis due to photoactivation of the photosensitizer conjugated to the nanoparticles. This method offers great diagnostic potential for highly proliferative tissues, including tumors. In additio…