Stability of Solid Lipid Nanoparticles in the Presence of Liquid Oil Emulsions

The dissolution of solid lipid nanoparticles (d ~200 nm, SLN) by mass transfer of lipid molecules from liquid oil emulsion droplets (d ~200 nm) was investigated by differential scanning calorimetry (DSC) and nuclear magnetic resonance spectroscopy (NMR). The mass transfer of n-tetradecane to n-eicosane SLN resulted in the dissolution of the SLN over the course of several hours. The rate of dissolution increased with the tetradecane droplet to eicosane SLN ratio and was greater in the presence of a micelle forming surfactant (i.e., polyoxyethylene sorbitan monolaurate) compared to a protein (i.e., sodium caseinate). The rate of mass transfer was slower in a triacyglycerol system (i.e., liquid droplets of Miglyol and solid droplets of palm stearin, SLN) but could be accelerated by the presence of isopropanol (1.4%) in the aqueous phase. This work shows that even if SLN can be stabilized against aggregation, they may still dissolve due to diffusion of the lipids through the aqueous phase. Even a partial dissolution of SLN can dramatically change their functionality as delivery systems.     

Measurement of Steep Surfaces Using White Light Interferometry

Abstract:  Scanning white light interferometry (SWLI) is an increasingly popular method to measure the surface profile of miniature components. Although it is tolerant to step changes in profile, its capability to measure the large surface gradients that are characteristic of high-aspect-ratio surfaces is limited. This is in part due to the numerical aperture of the objective lens which restricts the spatial frequency content of both the illumination and recorded fields. More fundamentally, though, SWLI instrumentation neglects the effects of multiple scattering and assumes that the field which illuminates the object is that which would be present if the object were absent. Although this is a reasonable approximation for slowly varying surfaces, it is generally not true for those with steep gradients. In this paper the 3D theory of SWLI is presented and the approximations made by current instrumentation are discussed in this context. Using finite element methods (FEM), SWLI interferograms are calculated, for the cases of 2D Silicon V-grooves and step artefacts, and the effects of multiple scattering are illustrated. Methods to improve the capability of SWLI to measure large surface gradients, first by tilting the sample and subsequently by using an iterative FEM model to provide improved estimates of the illuminating conditions are introduced.     

Effect of Liquid Oil on the Distribution and Reactivity of a Hydrophobic Solute in Solid Lipid Nanoparticles

The performance of solid lipid nanoparticles is often modified by the addition of small amounts of liquid oil. The effects of added liquid lipid (tetradecane, C14) on the distribution and reactivity of the spin probe 4-phenyl-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl nitroxide (PTMIO) in solid lipid nanoparticles (eicosane, C20) were investigated as a function of storage time and temperature. Emulsions prepared with blends of C14:C20 (100 % C14, 90 % C20, 99 % C20, and 100 % C20) and stabilized by sodium caseinate (1 wt%) were stored at 21.5 °C or 5 °C for 5 or 24 h prior to EPR analyses. In the liquid C14 droplets the PTMIO partitioned between the droplet and aqueous phases (70 and 30 %, respectively) independent of storage conditions. However, the proportion of probe in droplets decreased with increasing crystalline C20 concentration. The fraction of PTMIO in droplets containing C20 decreased in the following sequence: 5 h at room temperature >24 h at room temperature >24 h at refrigerated temperature and was lower in droplets with a higher proportion of C20. The residual PTMIO in semicrystalline droplets has higher polarity and lower mobility than PTMIO in liquid oil droplets suggesting it is in a layer surrounding the crystalline lipid core, and partly immobilized by interaction with the surface layer. The model of PTMIO distribution was consistent with the kinetics of PTMIO reduction by aqueous ascorbate ions.     

Stability and mechanism of whey protein soluble aggregates thermally treated with salts

The formation of whey protein aggregates, often termed soluble aggregates, with specific physicochemical properties has been shown to result in improved functionality in gels, foams, emulsions, encapsulation, films and coatings. This work evaluated the potential of whey protein soluble aggregates to improve thermal stability in the presence of salts and determine the mechanism of improved thermal stability. Solutions of whey protein isolate (WPI) or β-lactoglobulin (β-lg) (7% w/w, pH 6.8) were heated for 10 min at 90 °C to form soluble aggregates. Native proteins and soluble aggregates were diluted to 3% w/w in solutions containing 0–108 mM NaCl and thermally treated (90 °C, 5 min). Turbidity, solubility, and viscosity were evaluated, in addition to ζ-potential and S_o (surface hydrophobicity). Size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS) and dynamic light scattering were used to determine aggregate size and transmission electron microscopy (TEM) was used to evaluate aggregate shape. Use of soluble aggregates improved thermal stability due to their altered aggregate shape and higher charge, and resulted in final aggregates that were smaller and less dense, leading to reduced viscosity and turbidity, and increased solubility compared to native proteins. It is concluded that soluble aggregates formed under the appropriate conditions to produce the desirable physicochemical properties can be used to improve whey protein thermal stability with a possible application in beverages.     

Digital infarction in a patient with Raynaud''s phenomenon associated with treatment with a specific serotonin reuptake inhibitor. A case report

Palatopharyngeal injuries due to impaction of rigid objects held in the mouth are common. Most are essentially innocuous injuries requiring no specific treatment. However, there is the potential for perforation of the pharyngeal wall with the subsequent development of serious infection such as retropharyngeal abscess or mediastinitis. This possibility is more likely to be suspected in the presence of a visible laceration or puncture wound at the site of impact in the mouth or pharynx. We report three cases in which occult pharyngeal perforation occurred without any clinical signs of breech of the pharyngeal wall. In all cases a lateral soft tissue neck X-ray was diagnostic of perforation, showing the presence of retropharyngeal air. We, therefore, advocate the routine performance of soft tissue neck X-rays in all patients who present with a history of falling on a rigid object held in the mouth.     

A Polycomb-group gene regulates homeotic gene expression in Arabidopsis

Cell fate is determined when the commitment of cells to a particular fate is autonomously maintained, irrespective of their environment. In Drosophila, fate determination is maintained through the action of the Polycomb-group and trithorax-group genes, which are required so that states of homeotic gene activity are inherited through cell division. It is shown here that the CURLY LEAF gene of Arabidopsis is necessary for stable repression of a floral homeotic gene and encodes a protein with homology to the product of the Polycomb-group gene Enhancer of zeste. We suggest that Polycomb-group genes have a similar role in fate determination in plants and animals.     

The implications of the national curriculum for the use and management of IT resources in schools

Abstract  The introduction of a national curriculum in England, Wales and Northern Ireland is having a major effect on all schools. Information Technology is identified as a key area of this curriculum, not as a subject itself but as a theme which must permeate the curriculum. The implications are many and varied. An overview is provided of these issues, and indications given of the decisions that need to be made and the possible outcomes.