Influence of a pore-forming agent on swelling, network parameters, and permeability of poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-co-maleic acid) hydrogels:Application in transdermal delivery systems

We characterized hydrogels, prepared from aqueous blends of poly(methyl vinyl ether-co-maleic acid) (PMVE/MA) and poly(ethylene glycol) (PEG 10,000 Daltons) containing a pore-forming agent (sodium bicarbonate, NaHCO ). Increase in NaHCO content increased the equilibrium water content (EWC) and average molecular weight between crosslinks (M ) of hydrogels. For example, the %EWC was 731, 860, 1109, and 7536% and the M was 8.26, 31.64, 30.04, and 3010.00 × 10 g/mol for hydrogels prepared from aqueous blends containing 0, 1, 2, and 5% w/w of NaHCO , respectively. Increase in NaHCO content also resulted in increased permeation of insulin. After 24 h, percentage permeation was 0.94, 3.68, and 25.71% across hydrogel membranes prepared from aqueous blends containing 0, 2, and 5% w/w of NaHCO , respectively. Hydrogels containing the pore-forming agent were fabricated into microneedles (MNs) for transdermal drug delivery applications by integrating the MNs with insulin-loaded patches. It was observed that the mean amount of insulin permeating across neonatal porcine skin in vitro was 20.62% and 52.48% from hydrogel MNs prepared from aqueous blends containing 0 and 5% w/w of NaHCO . We believe that these pore-forming hydrogels are likely to prove extremely useful for applications in transdermal drug delivery of biomolecules. © 2012 Wiley Periodicals, Inc.

Density, conductivity, viscosity, and excess properties of (pyrrolidinium nitrate-based Protic Ionic Liquid + propylene carbonate) binary mixture

Density, ?, viscosity, ?, and conductivity, s, measurements of binary mixtures containing the pyrrolidinium nitrate Protic Ionic Liquid (PIL) and propylene carbonate (PC), are determined at the atmospheric pressure as a function of the temperature from (283.15 to 353.15) K and within the whole composition range. The temperature dependence of both the viscosity and conductivity of each mixture exhibits a non-Arrhenius behaviour, but is correctly fitted by using the Vogel–Tamman–Fulcher (VTF) equation. In each case, the best-fit parameters, such as the pseudo activation energy, View the MathML source and ideal glass transition temperature, T0 are then extracted. The excess molar volumes VE, and viscosity deviations from the ideality, ??, of each investigated mixture were then deduced from the experimental results, as well as, their apparent molar volumes, V?, thermal expansion coefficients ap, and excess Gibbs free energies (?G*E) of activation of viscous flow. The VE, apE, ?? values are negative over the whole composition range for each studied temperature therein. According to the Walden rule, the ionicity of each mixture was then evaluated as a function of the temperature from (283.15 to 353.15) K and of the composition. Results have been then discussed in terms of molecular interactions and molecular structures in this binary mixture.

A Molecular Dynamics Study of the Early Stages of Calcium Carbonate Growth

The precipitation of calcium carbonate in water has been examined using a combination of molecular dynamics and umbrella sampling. During 20 ns molecular dynamics trajectories at elevated calcium carbonate concentrations, amorphous particles are observed to form and appear to be composed of misaligned domains of vaterite and aragonite. The addition of further calcium ions to these clusters is found to be energetically favorable and virtually barrierless. By contrast, there is a large barrier to the addition of calcium to small calcite crystals. Thus, even though calcite nanocrystals are stable in solution, at high supersaturations, particles of amorphous material form because this material grows much faster than ordered calcite nanocrystals.

Binding of Calcium and Carbonate to Polyacrylates

Polyacrylate molecules can be used to slow the growth of calcium carbonate. However, little is known about the mechanism by which the molecules impede the growth rate. A recent computational study (Bulo et al. Macromolecules 2007, 40, 3437) used metadynamics to investigate the binding of calcium to polyacrylate chains and has thrown some light on the coiling and precipitation of these polymers. We extend these simulations to examine the binding of calcium and carbonate to polyacrylate chains. We show that calcium complexed with both carbonate and polyacrylate is a very stable species. The free energies of calcium-carbonate-polyacrylate complexes, with different polymer configurations, are calculated, and differences in the free energy of the binding of carbonate are shown to be due to differences in the amount of steric hindrance about the calcium, which prevents the approach of the carbonate ion.

TAP studies on 2% Ag/gamma-Al2O3 catalyst for selective reduction of oxygen in a H-2-rich ethylene feed

Catalysts currently employed for the polymerization of ethylene have previously been found to deactivate in the presence of oxygen. It is, therefore, important that oxygen is removed from the ethylene feedstock prior to the polymerization. The Ag/gamma-Al2O3 catalyst exhibits excellent activity and selectivity toward oxygen reduction with hydrogen in the presence of ethylene. TAP vacuum pulse experiments have been utilised to understand the catalytic behaviour of the Ag/gamma-Al2O3 catalyst. TAP multi-pulse experiments have determined the types of active sites that are found on the Ag/gamma-Al2O3 catalyst, and the intrinsic activity of these sites. The lifetime of the reactive adsorbed oxygen intermediate has also been determined through TAP consecutive pulse experiments. Multi-pulse and consecutive pulse data have been combined with ethylene adsorption/desorption rate constants to provide an overview of the Ag/gamma-Al2O3 catalyst system.

Preparation of highly stable oligo (ethylene glycol) derivatives-functionalized gold nanoparticles and their application in LSPR-Based detection of PSA/ACT complex

A sandwich immunoassay for PSA/ACT complex detection based on gold nanoparticle aggregation using two probes was developed. The functionalized colloidal gold nanoparticles (AuNPs) showed highly stable not only in the presence of high ionic strength but also in a wide pH range. The functionalized AuNPs were tagged with PSA/ACT complex monoclonal antibody and goat PSA polyclonal antibody and served as the probes to induce aggregation of the colloidal particles. As a result, PSA/ACT complex was detected at concentrations as low as 1 ng/ml. This is the first time that a new aggregation sandwich-immunoassay technique using two gold probes has been used, and the results are generally applicable to other LSPR-based immunoassays.

Modelling of poly(ethylene terephthalate) in injection stretch-blow moulding

Simulations of the injection stretch-blow moulding process have been developed for the manufacture of poly(ethylene terephthalate) bottles using the commercial finite element package ABAQUS/standard. Initially a simulation of the manufacture of a 330 mL bottle was developed with three different material models (hyperelastic, creep, and a non-linear viscoelastic model (Buckley model)) to ascertain their suitability for modelling poly(ethylene terephthalate). The Buckley model was found to give results for the sidewall thickness that matched best with those measured from bottles off the production line. Following the investigation of the material models, the Buckley model was chosen to conduct a three-dimensional simulation of the manufacture of a 2 L bottle. It was found that the model was also capable of predicting the wall thickness distribution accurately for this bottle. In the development of the three-dimensional simulation a novel approach, which uses an axisymmetric model until the material reaches the petaloid base, was developed. This resulted in substantial savings in computing time. © 2000 IoM Communication Ltd.