Aggregation of nanoparticles in a block copolymer bilayer

Dissipative particle dynamics simulations in colloid and Interface science: a review

Dissipative particle dynamics (DPD) is one of the most efficient mesoscale coarse-grained methodologies for modeling soft matter systems. Here, we comprehensively review the progress in theoretical formulations, parametrization strategies, and applications of DPD over the last two decades. DPD bridges the gap between the microscopic atomistic and macroscopic continuum length and time scales. Numerous efforts have been performed to improve the computational efficiency and to develop advanced versions and modifications of the original DPD framework. The progress in the parametrization techniques that can reproduce the engineering properties of experimental systems attracted a lot of interest from the industrial community longing to use DPD to characterize, help design and optimize the practical products. While there are still areas for improvements, DPD has been efficiently applied to numerous colloidal and interfacial phenomena involving phase separations, self-assembly, and transport in polymeric, surfactant, nanoparticle, and biomolecules systems.

Salecan-Clay Based Polymer Nanocomposites for Chemotherapeutic Drug Delivery Systems; Characterization and In Vitro Biocompatibility Studies

Salecan is a microbial polysaccharide suitable to obtain hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility properties. In this work, Salecan of different concentrations was introduced into polymethacrylic acid (PMAA) in the presence of clay to form novel semi synthetic hydrogel nanocomposites systems and loaded afterwards with doxorubicin (DOX). The physical-chemical characteristics of the nanocomposites systems and their effect on the viability, and morphology of MDBK (Madin-Darby bovine kidney), HT-29 human colorectal adenocarcinoma and Colo 205 human colon adenocarcinoma cell lines were investigated. DOX release from the nanocomposite systems, cell up-take and subsequent effect on cell proliferation was also analyzed. It was found that Salecan concentration determined the swelling behavior, structural parameters and morphological features of the nanocomposite systems. The hydrogen bonds strongly influenced the formation of PMAA-Salecan-clay systems, each component bringing its own contribution, thus demonstrating the achievement of an advanced crosslinked network and a more compacted hydrogel nanocomposite morphology. All the synthesized nanocomposites had negligible toxicity to normal MDBK cells and chemoresistent HT-29 cell line, whereas in the case of Colo 205 cells a decrease by 40% of the cell viability was obtained for the sample containing the highest amount of Salecan. This effect was correlated with the lowest pore size distribution leading to highest available specific surface area and entrapped amount of DOX which was further released from the nanocomposite sample. Corroborating all the data it can be suggested that the synthesized nanocomposites with Salecan and clay could be good candidates as vehicles for chemotherapeutic agents.

Design of Novel Oligomeric Mixed Ligand Complexes: Preparation, Biological Applications and the First Example of Their Nanosized Scale

A successful oligomerization of ternary metal complexes, cobalt (II), nickel (II), copper (II), zinc (II), chromium (III) and ferric sulfate (III) with nitrilotriacetic acid (NTA) as a primary ligand and glutamic acid as a secondary ligand, has been demonstrated. The formation of oligomers arose from the presence of the sulfate moiety, which operates as a bridged bidentate ligand that coordinates with other metal moieties. The novel oligomers exhibited octahedral structures, which bonded together through the sulfate moiety. In silico predictions were conducted to gauge the bioactivity, physico-chemical and pharmacokinetic properties. The biological activities of these oligomers as well as their tumor inhibitory behavior have been explored. This work also presents a facile and novel method of preparing these materials in nanosize, using Cetyltrimethylammonium bromide (CTAB) and polyvinyl alcohol (PVA) as capping ligands. The size and shape of the nanomaterials have been confirmed using the transmission electron microscope (TEM) and the scanning electron microscope (SEM).

Composite materials based on Ag nanoparticles in situ synthesized on the vaterite porous matrices

We have designed sensors based on Ag nanoparticles synthesized in situ on the vaterite beads. In this article we demonstrate an approach to produce size controllable spherical and elliptical vaterite particles and discuss time-dependent in situ Ag nanoparticles synthesis and its potential effect on surface-enhanced Raman scattering. The time dependent silver reduction synthesis in inorganic porous particles allows to regulate the number and size of Ag nanoparticles. It is shown that the irregular surface and high porosity of vaterite particles and large amount (surface filling factor) of the Ag nanoparticles are the critical parameters to increase the SERS signal to 10⁴ times. Such inorganic composites have a huge potential in medical applications; soon they provide an opportunity to study intracellular processes in vivo. The detailed characterization of the microstructure of these composites was studied by scanning and transmission electron microscopy, including 3D visualization and energy dispersive x-ray microanalysis.

Stereocomplex formation in mixed polymers filled with two-dimensional nanofillers

Nanosheets promote the formation of stereocomplex crystallites due to the heterogeneous nucleation of mixed polymer chains on filler surfaces.

Ferroelectric-mediated filamentary resistive switching in P(VDF-TrFE)/ZnO nanocomposite films

Organic ReRAMs based on ferroelectric P(VDF-TrFE) and ZnO NPs blends exhibiting bipolar resistive switching and a high ON/OFF ratio were realized using a low-cost solution process.

Nano-structured magneto-responsive membranes from block copolymers and iron oxide nanoparticles

Preparation of porous membranes from PMAA-b-PMMA copolymers and magnetic iron oxide nanoparticles and their performance under magnetic fields.

Suppression of target patterns in domain aligned cold-zone annealed block copolymer films with immobilized film-spanning nanoparticles

We examine the effect of a moving in-plane temperature gradient on the ordering of cylinder-forming block-copolymers (BCP) in films containing immobilized nanoparticles that span the film thickness. In a previous paper, we reported the effect of static step oven-annealing of these films above the glass transition temperature Tg for a long period before ordering the BCP film at a much higher temperature. In the dynamic film annealing method of the present work, termed cold zone annealing (CZA), the material is continuously raised to a temperature somewhat above the glass transition temperature and then well above it, with a control of the heating time and thermal gradient. Oven annealing before ordering has been found to relieve residual stresses in the film associated with large thermal expansion of the film upon heating, eliminating the large scale target patterns induced by stresses effects associated with residual solvent and thermal expansion. By comparison, CZA naturally suppresses undesirable target patterning with enhanced ordering kinetics created through this thermal history.

Phase transition in dimer liquids

We study the phase transition in a system composed of dimers interacting with each other via a nearest-neighbor (NN) exchange J and competing interactions taken from a truncated dipolar coupling. Each dimer occupies a link between two nearest sites of a simple cubic lattice. We suppose that dimers are self-avoiding and can have only three orientations, which coincide with the x, y or z direction. The interaction J is attractive if the two dimers are parallel to each other at the NN distance, zero otherwise. The truncated dipolar interaction is characterized by two parameters: its amplitude D and the cutoff distance rc. Using the steepest descent method, we determine the ground-state (GS) configuration as functions of D and rc. We then use Monte Carlo simulations to investigate the nature of the low-temperature phase and to determine characteristics of the phase transition from the ordered phase to the disordered phase at high temperatures at a given dimer concentration. We show that as the temperature increases, dimers remain in the compact state and the transition from the low-T compact phase to the disordered phase where dimers occupy the whole space is of second order when D is small, but becomes of first order for large enough D, for both polarized and nonpolarized dimers. This transition has a resemblance to the unfolding polymer transition. The effect of rc is discussed.

The influence of size, shape and vessel geometry on nanoparticle distribution

Nanoparticles (NPs) are emerging as promising carrier platforms for targeted drug delivery and imaging probes. To evaluate the delivery efficiency, it is important to predict the distribution of NPs within blood vessels. NP size, shape and vessel geometry are believed to influence its biodistribution in circulation. Whereas, the effect of size on nanoparticle distribution has been extensively studied, little is known about the shape and vessel geometry effect. This paper describes a computational model for NP transport and distribution in a mimetic branched blood vessel using combined NP Brownian dynamics and continuum fluid mechanics approaches. The simulation results indicate that NPs with smaller size and rod shape have higher binding capabilities as a result of smaller drag force and larger contact area. The binding dynamics of rod-shaped NPs is found to be dependent on their initial contact points and orientations to the wall. Higher concentration of NPs is observed in the bifurcation area compared to the straight section of the branched vessel. Moreover, it is found that Péclet number plays an important role in determining the fraction of NPs deposited in the branched region and the straight section. Simulation results also indicate that NP binding decreases with increased shear rate. Dynamic NP re-distribution from low to high shear rates is observed due to the non-uniform shear stress distribution over the branched channel. This study would provide valuable information for NP distribution in a complex vascular network.