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In cases of aortic stenosis, bioprosthetic heart valves (BHVs), with glutaraldehyde-fixed bovine pericardium leaflets (GLBP), are often implanted to replace the native diseased valve. Widespread use of BHVs, however, is restricted due to inadequate long-term durability, owing specifically to premature leaflet failure. Mechanical fatigue damage and calcification remain the primary leaflet failure modes, where glutaraldehyde treatment is known to accelerate calcification. The literature in this area is limited, with some studies suggesting mechanical damage increases calcification and others that they are independent degenerative mechanisms. In this study, specimens which were non-destructively pre-sorted according to collagen fibre architecture and uniaxially cyclically loaded until failure or 1 million cycles, were placed in an in vitro calcification solution. The weakest specimen group (those with fibres aligned perpendicular to the load) had statistically significantly higher volumes of calcification when compared to those with a high fatigue life. Moreover, SEM imaging revealed that ruptured and damaged fibres presented calcium binding sites; resulting in 4 times more calcification in fractured samples in comparison to those which did not fail by fatigue. To the authors’ knowledge, this study quantifies for the first time, that mechanical damage drives calcification in commercial-grade GLBP and that calcification varies spatially according to localised damage levels. These findings illustrate that not only is calcification of GLBP exacerbated by fatigue damage, but that both failure phenomena are underpinned by the collagen fibre organisation. Consequently, controlling for GLBP collagen fibre architecture in leaflets could minimise the progression of these primary failure modes in patient BHVs. Statement of significance Mechanical damage and calcification are the primary premature failure modes of glutaraldehyde-fixed bovine pericardial (GLBP) leaflets in bioprosthetic heart valves. In this study, commercial-grade GLBP specimens which were uniaxially cyclically loaded to failure or 1 million cycles, were placed in an in vitro calcification solution. MicroCT and SEM analysis showed that localised calcification levels varied spatially according to damage, where ruptured fibres offered additional calcium binding sites. Furthermore, specimens with a statistically significant lower fatigue life were associated with statistically significant higher calcification. This study revealed that mechanical damage drives calcification of GLBP. Non-destructive pre-screening of collagen fibres demonstrated that both the fatigue life and calcification potential of commercial-grade GLBP, are underpinned by the collagen fibre architecture.

Although the route of sensitization to food allergens is still the subject of debate, it is generally accepted the gut immune system plays a pivotal role. However, hitherto the transport of allergens across the normal, pre-sensitized gut epithelium remained largely unknown. Our aim was to identify the route through which protein bodies and soluble proteins from digested peanuts penetrated the pre-sensitized gut epithelium in vivo and the specific cell types involved in the transport. Digestion of peanuts released a large number of protein bodies that are exclusively transported across the epithelium by specialized antigen-sampling M cells and delivered to the lymphoid tissue of Peyer's patch. Intracellular transport of soluble protein also occurred almost exclusively via M cells and it was negligible across absorptive enterocytes. We hypothesize that these conditions which are known to favour strongly the induction of immune responses rather than oral tolerance may play a significant role in the genesis of allergic reactions.

Oligogalacturonates were produced by the limited enzymic hydrolysis of polygalacturonic acid and purified by ion-exchange chromatography. The fractions obtained were of limited polydispersity, determined by analytical ion-exchange chromatography. Oligomers with an average degree of polymerization of 10–15 were readily crystallized from aqueous salt solutions at neutral pH as single crystals. Crystal morphology of the salts examined, Na + , K + and Ca 2+ were characteristic of the salt. The wide-angle X-ray diffraction patterns obtained for the sodium salt were consistent with published fibre diffraction data of this salt form.

Patient specific computational analyses can aid in preoperative planning and long term evaluation of asymmetric deployed Transcatheter Aortic Valves (TAV) in calcified aortic annuli. In this study we developed and validated a preclinical computational tool to predict the performance of TAVs in vivo

The creaming behaviour of model pourable salad dressings has been studied over a wide range of xanthan and oil phase concentrations. They were produced by mixing a colloidally stable emulsion with xanthan solutions. The model dressings were completely flocculated by depletion at all xanthan concentrations >0.1 g/l. Creaming behaviour was in three phases: an initial delay phase, followed by more or less linear creaming and finally cream compression. Delayed creaming has not been reported previously. It is of great practical interest, because a complete absence of creaming is the aim of successful dressing formulation. The length of the delay phase was proportional to the emulsion concentration, inversely proportional to the oil/aqueous phase density difference and scaled over more than four orders of magnitude with the xanthan concentration to powers between 3 and 4. Traditionally, the stabilisation of salad dressing by xanthan is explained by the yield stress of its solutions. It is shown that they do not have one, and we offer an alternative explanation. It is suggested that the depletion flocculation of the emulsion droplets, induced by the addition of xanthan, leads to the formation of a particle network and that it is the time-dependent yield stress of this network which stabilises the dressing.

We report a study of the creaming behavior of an alkane-in-water emulsion at varying oil volume fractions in the presence of the nonadsorbing polymer, hydroxyethylcellulose (HEC). Pairwise interaction potentials predict a shallow secondary minimum for this system arising from the attractive potential produced by the so-called depletion effect. Use of an ultrasonic creaming monitor has allowed us to verify the predicted flocculation and quantify the separation of the system into colloidrich and colloid-poor phases. The phase diagram for 20.2% v/v oil and varying polymer concentrations has been determined. At 0.02% w/w HEC we have investigated the effect of oil volume fraction on the phase composition of the system. The observed behavior has been compared with that predicted from the available theoretical treatments for phase separation but with due regard to the possible effects of polydispersity.

The creaming of concentrated alkane-in-water emulsions stabilised by a non-ionic surfactant has been measured in the presence of hydroxyethylcellulose polysaccharide. Creaming rates under gravity were determined by visual observation. In the emulsions containing polysaccharide the creaming was much more rapid than expected from consideration of the oil droplet size, density difference, the rheological properties of the continuous phase and the current oil concentration. Flocculation effects would appear to be the primary mechanism for the anomalous behaviour, although other effects cannot be entirely ruled out at this stage. The final oil concentrations in the creamed emulsion phases have also been measured, and an interpretation is given in terms of the pressure in the cream, the droplet size and the interfacial tension.

The anionic polysaccharide xanthan, widely used as a stabilizer in food dispersions, induces flocculation by a depletion mechanism. The effect of flocculation, induced by the presence of xanthan, on the gravitational destabilization (creaming and compaction) of 20% oil-in-water emulsions is presented. The detailed gravitational destabilization processes are studied by following changes in the concentration profile with time. In the absence of flocculant the polydisperse droplets rise as a diffuse meniscus and form a cream of ~70% oil at the top of the sample. Such behaviour is consistent with creaming in a dispersion of non-interacting polydisperse particles. In contrast the flocculated droplets form a sharp meniscus and cream rapidly. At the top of the sample the floes form a less concentrated cream which undergoes compaction under gravity. The compaction is characterized by a concentration-dependent bulk modulus.