Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in -dodecane with varying water content onto iron oxide.

The self-assembly and surface adsorption of glycerol monooleate (GMO) in -dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics.

Diblock bottlebrush polymer in a non-polar medium: Self-assembly, surface forces, and superlubricity.

Whilst bottlebrush polymers have been studied in aqueous media for their conjectured role in biolubrication, surface forces and friction mediated by bottlebrush polymers in non-polar media have not been previously reported. Here, small-angle neutron scattering (SANS) showed that a diblock bottlebrush copolymer (oligoethyleneglycol acrylate/ethylhexyl acrylate; OEGA/EHA) formed spherical core-shell aggregates in n-dodecane (a model oil) in the polymer concentration range 0.1-2.

Surface forces and friction between Langmuir-Blodgett polymer layers in a nonpolar solvent.

Optimization of boundary lubrication by tuning the confined molecular structures formed by surface-active additives such as surfactants and polymers is of key importance to improving energy efficiency in mechanical processes. Here, using the surface forces apparatus (SFA), we have directly measured the normal and shear forces between surface layers of a functionalised olefin copolymer (FOCP) in n-dodecane, deposited onto mica using the Langmuir-Blodgett (LB) technique. The FOCP has an olefin backbone decorated with a statistical distribution of polar-aromatic groups, with a structure that we term as "centipede".

Towards a neutron and X-ray reflectometry environment for the study of solid-liquid interfaces under shear.

A novel neutron and X-ray reflectometry sample environment is presented for the study of surface-active molecules at solid-liquid interfaces under shear. Neutron reflectometry was successfully used to characterise the iron oxide-dodecane interface at a shear rate of [Formula: see text] [Formula: see text] using a combination of conventional reflectometry theory coupled with the summation of reflected intensities to describe reflectivity from thicker films. Additionally, the structure adopted by glycerol monooleate (GMO), an Organic Friction Modifier, when adsorbed at the iron oxide-dodecane interface at a shear rate of [Formula: see text] [Formula: see text] was studied.

Thiol-Bromo Click Reaction for One-Pot Synthesis of Star-Shaped Polymers.

Star-shaped polymers have unique physical properties and they are sought after materials in industry. However, the ease of synthesis is essential for translation of these materials into large-scale applications. Herein, a highly efficient synthetic method to prepare star-shaped polymers by combination of Cu-mediated reversible deactivation radical polymerization (Cu-RDRP) and thiol-bromo click reaction is described.

Segregation Interdigitation in Highly Dynamic Polymer/Surfactant Layers.

Many polymer/surfactant formulations involve a trapped kinetic state that provides some beneficial character to the formulation. However, the vast majority of studies on formulations focus on equilibrium states. Here, nanoscale structures present at dynamic interfaces in the form of air-in-water foams are explored, stabilised by mixtures of commonly used non-ionic, surface active block copolymers (Pluronic) and small molecule ionic surfactants (sodium dodecylsulfate, SDS, and dodecyltrimethylammonium bromide, CTAB).

The effect of thiamine-coating nanoparticles on their biodistribution and fate following oral administration.

Thiamine-coated nanoparticles were prepared by two different preparative methods and evaluated to compare their mucus-penetrating properties and fate in vivo. The first method of preparation consisted of surface modification of freshly poly(anhydride) nanoparticles (NP) by simple incubation with thiamine (T-NPA). The second procedure focused on the preparation and characterization of a new polymeric conjugate between the poly(anhydride) backbone and thiamine prior the nanoparticle formation (T-NPB).

Assembly of small molecule surfactants at highly dynamic air-water interfaces.

Small-angle neutron scattering has been used to probe the interfacial structure of foams stabilised by small molecule surfactants at concentrations well below their critical micelle concentration. The data for wet foams showed a pronounced Q dependence at low Q and noticeable inflexions over the mid Q range. These features were found to be dependent on the surfactant structure (mainly the alkyl chain length) with various inflexions across the measured Q range as a function of the chain length but independent of factors such as concentration and foam age/height.

Linking micellar structures to hydrogelation for salt-triggered dipeptide gelators.

Some functionalised dipeptides can form hydrogels when salts are added to solutions at high pH. We have used surface tension, conductivity, rheology, optical, confocal and scanning electron microscopy, (1)H NMR and UV-Vis spectroscopy measurements to characterise fully the phase behaviour of solutions of one specific gelator, 2NapFF, at 25 °C at pH 10.5.

In Vitro Evaluation of the Interaction of Dextrin-Colistin Conjugates with Bacterial Lipopolysaccharide.

Dextrin-colistin conjugates have been developed with the aim of achieving reduced clinical toxicity associated with colistin, also known as polymyxin E, and improved targeting to sites of bacterial infection. This study investigated the in vitro ability of such dextrin-colistin conjugates to bind and modulate bacterial lipopolysaccharide (LPS), and how this binding affects its biological activity. These results showed that colistin and amylase-activated dextrin-colistin conjugate to a lesser extent induced aggregation of LPS to form a stacked bilayer structure with characteristic dimensions, although this did not cause any substantial change in its secondary structure.

Disarmed anthrax toxin delivers antisense oligonucleotides and siRNA with high efficiency and low toxicity.

Inefficient cytosolic delivery and vector toxicity contribute to the limited use of antisense oligonucleotides (ASOs) and siRNA as therapeutics. As anthrax toxin (Atx) accesses the cytosol, the purpose of this study was to evaluate the potential of disarmed Atx to deliver either ASOs or siRNA. We hypothesized that this delivery strategy would facilitate improved transfection efficiency while eliminating the toxicity seen for many vectors due to membrane destabilization.

Probing competitive interactions in quaternary formulations.

Hypothesis: The interaction of amphiphilic block copolymers of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) group with small molecule surfactants may be "tuned" by the presence of selected alcohols, with strong interactions leading to substantial changes in (mixed) micelle morphology, whilst weaker interactions lead to coexisting micelle types.

Experiments: The nature and the strength of the interactions between Pluronic P123 (EO20PO70EO20) and small molecule surfactants (anionic sodium dodecylsulfate, SDS, C12SO4Na), (cationic dodecyltrimethylammonium bromide, C12TAB) and (non-ionic polyoxyethylene(23)lauryl ether, Brij 35, C12EO23OH) is expected to depend on the partitioning of the short, medium and long chain alcohols (ethanol, hexanol and decanol respectively) and was probed using tensiometry, pulsed-gradient spin-echo nuclear magnetic resonance (PGSE-NMR) and small-angle neutron scattering (SANS).

Findings: The SANS data for aqueous P123 solutions with added alcohols were well described by a charged spherical core/shell model for the micelle morphology.

Probing the interaction of nanoparticles with mucin for drug delivery applications using dynamic light scattering.

Drug delivery via the eye, nose, gastrointestinal tract and lung is of great interest as they represent patient-compliant and facile methods to administer drugs. However, for a drug to reach the systemic circulation it must penetrate the "mucus barrier". An understanding of the characteristics of the mucus barrier is therefore important in the design of mucus penetrating drug delivery vehicles e.

Interpolymer complexation: comparisons of bulk and interfacial structures.

The interactions between the strong polyelectrolyte sodium poly(styrenesulfonate), NaPSS, and the neutral polymer poly(vinylpyrrolidone), PVP, were investigated in bulk and at the silica/solution interface using a combination of diffusion nuclear magnetic resonance spectroscopy (NMR), small-angle neutron scattering (SANS), solvent relaxation NMR, and ellipsometry. We show for the first time that complex formation occurs between NaPSS and PVP in solution; the complexes formed were shown not to be influenced by pH variation, whereas increasing the ionic strength increases the complexation of NaPSS but does not influence the PVP directly. The complexes formed contained a large proportion of NaPSS.

Nanoparticle diffusion within intestinal mucus: Three-dimensional response analysis dissecting the impact of particle surface charge, size and heterogeneity across polyelectrolyte, pegylated and viral particles.

Multiple particle tracking (MPT) methodology was used to dissect the impact of nanoparticle surface charge and size upon particle diffusion through freshly harvested porcine jejunum mucus. The mucus was characterised rheologically and by atomic force microscopy. To vary nanoparticle surface charge we used a series of self-assembly polyelectrolyte particles composed of varying ratios of the negatively charged polyacrylic acid polymer and the positively charged chitosan polymer.

Nanoparticles decorated with proteolytic enzymes, a promising strategy to overcome the mucus barrier.

The intestinal mucus gel layer represents a stumbling block for drug adsorption. This study is aimed to formulate a nanoparticulate system able to overcome this barrier by cleaving locally the glycoprotein substructures of the mucus. Mucolytic enzymes such as papain (PAP) and bromelain (BRO) were covalently conjugated to poly(acrylic acid) (PAA).

Methods to determine the interactions of micro- and nanoparticles with mucus.

The present review provides an overview of methods and techniques for studying interactions of micro- and nanoparticulate drug delivery system with mucus. Nanocarriers trapped by mucus are featuring a change in particle size and zeta potential that can be utilized to predict their mucus permeation behavior. Furthermore, interactions between nanoparticulate drug delivery systems and mucus layer modify the viscoelasticity of mucus which can be detected via rheological studies and quartz crystal microbalance with dissipation monitoring (QCM-D) analysis.

The effect of solvent choice on the gelation and final hydrogel properties of Fmoc-diphenylalanine.

Gels can be formed by dissolving Fmoc-diphenylalanine (Fmoc-PhePhe or FmocFF) in an organic solvent and adding water. We show here that the choice and amount of organic solvent allows the rheological properties of the gel to be tuned. The differences in properties arise from the microstructure of the fibre network formed.

The effect of self-sorting and co-assembly on the mechanical properties of low molecular weight hydrogels.

Self-sorting in low molecular weight hydrogels can be achieved using a pH triggered approach. We show here that this method can be used to prepare gels with different types of mechanical properties. Cooperative, disruptive or orthogonal assembled systems can be produced.

Adsorption and surfactant-mediated desorption of poly(vinylpyrrolidone) on plasma- and piranha-cleaned silica surfaces.

Optical flow cell reflectometry was used to study the adsorption of poly(vinylpyrrolidone) (PVP) to a silica surface and the subsequent surfactant adsorption and polymer desorption upon exposure to the anionic surfactant sodium dodecyl sulfate (SDS). We have studied these effects as a function of pH and surfactant concentration, but also for two different methods of silica preparation, O2 plasma and piranha cleaning. As a function of pH, a plateau in the amount adsorbed of ∼0.

Construction and physiochemical characterisation of a multi-composite, potential oral vaccine delivery system (VDS).

An increasing human population requires a secure food supply and a cost effective, oral vaccine delivery system for livestock would help facilitate this end. Recombinant antigen adsorbed onto silica beads and coated with myristic acid, was released (∼15% (w/v)) over 24 h at pH 8.8.

The influence of the kinetics of self-assembly on the properties of dipeptide hydrogels.

We discuss the effect of the kinetics of pH change on the mechanical properties of dipeptide hydrogels. Data from other peptide-based low molecular weight gelator (LMWG) systems suggest that the rheological properties are often highly dependent on the assembly rate. To examine kinetics here, we have used the hydrolysis of glucono-8-lactone (GdL).

Manipulating interfacial polymer structures through mixed surfactant adsorption and complexation.

The effects of a nonionic alcohol ethoxylate surfactant, C(13)E(7), on the interactions between PVP and SDS both in the bulk and at the silica nanoparticle interface are studied by photon correlation spectroscopy, solvent relaxation NMR, SANS, and optical reflectometry. Our results confirmed that, in the absence of SDS, C(13)E(7) and PVP are noninteracting, while SDS interacts strongly both with PVP and C(13)E(7) . Studying interfacial interactions showed that the interfacial interactions of PVP with silica can be manipulated by varying the amounts of SDS and C(13)E(7) present.

Surfactant-mediated desorption of polymer from the nanoparticle interface.

The surfactant-mediated desorption of adsorbed poly(vinylpyrrolidone), PVP, from anionic silica surfaces by sodium dodecyl sulfate, SDS, was observed. While photon correlation spectroscopy shows that the size of the polymer-surfactant-particle ensemble grows with added SDS, a reduction in the near-surface polymer concentration is measured by solvent relaxation NMR. Volume fraction profiles of the polymer layer extracted from small-angle neutron scattering experiments illustrate that the adsorbed polymer layer has become more diffuse and the polymer chains more elongated as a result of the addition of SDS.