Stimulus-responsive liquids for encapsulation storage and controlled release of drugs from nano-shell capsules

Narrow escape problem for Brownian particles in a microsphere with internal circulation

This paper considers the narrow escape problem of a Brownian particle within a two-dimensional domain with two escape windows and an internal circulation modeled by the flow within a Hill's vortex. To account for the spatially inhomogeneous flow within the domain, a Lagrangian study is undertaken using the complete equations of motion for a dense particle which is necessary to distinguish between the various regimes as the strength of the internal circulation is varied. For very low internal circulation the particle undergoes the conventional narrow escape problem, and agreement is good with the asymptotic expression. As the internal circulation is increased, regimes are identified with different scaling for the mean escape time. The potential application of this for drug delivery (were nanoparticles are encased in a microsphere) is discussed.

Dielectric analysis of the upper critical solution temperature behaviour of a poly(acrylamide-co-acrylonitrile) copolymer system in water

A copolymer consisting of acrylamide (AAm) and acrylonitrile (AN) in aqueous solution was investigated using broadband dielectric spectroscopy at frequencies between 10^-1 Hz and 10⁶ Hz in the temperature range from 2 °C to 60 °C. This system shows an UCST phase behavior. The phase transition and aggregation behavior is monitored by both the temperature and frequency dependence of the complex conductivity σ*(f, T), where the AN fraction and the concentration of the solution were varied. Additionally, the dielectric data are compared with the results obtained from dynamic light scattering measurements. The temperature dependence of the DC conductivity (σ_DC) of the copolymer solution is monitored and the phase transition temperature (PTT) of the poly(AAm-co-AN) copolymer is deduced from a change in the T-dependence of the DC conductivity. The change in σ_DC can be explained by decreased effective charge carrier mobility and a reduction of the effective charge number density at temperatures below the phase transition temperature of the poly(AAm-co-AN) solution. A pronounced interfacial polarization effect on the frequency dependence of the real part of the conductivity (σ') is observed at temperatures below the phase transition temperature. The charge carriers are blocked at the formed aggregates giving rise to this interfacial polarization. The dependence of the interfacial polarization on the acrylonitrile fraction in the copolymer and the concentration of the solution is studied in detail and conclusions concerning the internal structures of the copolymer aggregates are drawn.

The effect of needle tip displacement in co-axial electrohydrodynamic processing

Co-axial electrospraying and electrospinning are versatile electrohydrodynamic (EHD) techniques that can be used to encapsulate a variety of materials in the form of polymeric particles and fibres via a one step process.

In situ preparation and protein delivery of silicate-alginate composite microspheres with core-shell structure

The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS-A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS-A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS-A microspheres prepared by non-in situ method, which lack a core-shell structure. CS-A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS-A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS-A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS-A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.