Encapsulation of magnetic nanoparticles in a pH-sensitive poly(4-vinyl pyridine) polymer: a step forward to a multi-responsive system

A multiresponsive system that consists on pH-responsive polymer microspheres with encapsulated iron oxide magnetic nanoparticles that rendered the core magnetic to enable externally controlled actuation under magnetic induction has been developed. The inorganic nanoparticles were first prepared and, then, further encapsulated in a pH-sensitive poly(4-vinylpyridine). These spheres have been obtained by a modification of the simple, rapid and high-reproducible nanoprecipitation method. Magnetic measurements showed that the iron oxide nanoparticles are superparamagnetic and, therefore, able to undergo a local increase of the temperature when an oscillating magnetic field is applied. Magnetically triggered heating and pH sensitivity can be useful for biomedical applications.     

Delivery of chemotropic proteins and improvement of dopaminergic neuron outgrowth through a thixotropic hybrid nano-gel

Chemotropic proteins guide neuronal projections to their final target during embryo development and are useful to guide axons of neurons used in transplantation therapies. Site-specific delivery of the proteins however is needed for their application in the brain to avoid degradation and pleiotropic affects. In the present study we report the use of Poly (ethylene glycol)-Silica (PEG-Si) nanocomposite gel with thixotropic properties that make it injectable and suitable for delivery of the chemotropic protein semaphorin 3A. PEG-Si gel forms a functional gradient of semaphorin that enhances axon outgrowth of dopaminergic neurons from rat embryos or differentiated from stem cells in culture. It is not cytotoxic and its properties allowed its injection into the striatum without inflammatory response in the short term. Long term implantation however led to an increase in macrophages and glial cells. The inflammatory response could have resulted from non-degraded silica particles, as observed in biodegradation assays.     

Influence of Texture on Taste: Insights Gained During Studies of Hardness, Juiciness, and Sweetness of Apple Fruit

Apple flesh can be considered as a living structure within which juice and tastants are encapsulated in individual cells. The breakdown of this structure and release of juice varies between hard and soft apples. We hypothesized that the texture of the fruit and the way it releases juice during chewing would therefore influence the perception of sweetness. Time‐intensity (TI) techniques were used by a trained panel to study the temporal changes in the intensity of “juiciness” and “sweetness” during consumption of apples that varied in mechanical hardness (measured by puncture test). All apple samples had a similar water content, but the pattern of juice release was markedly different. Juice was released into the mouth in a pattern of increasing and then deceasing intensity. The maximum intensity (Imax), duration of the stimulus (DUR), and area under the TI curve (AUC) were significantly higher for hard compared with soft apples. The impact of juice release on perception of sweetness was examined using apples in which the Imax and AUC for juiciness of soft apples were half the value of those for firm apples. There was no consistent difference in Imax, DUR, or AUC for sweet taste in these 2 sets of apples. We concluded that sufficient juice was released from soft and less juicy apples to ensure that sweetness perception was maximized. These results are discussed in relation to earlier studies that demonstrated that texture (thickening agents) suppresses flavor perception in solutions and juices.     

Structural studies on the lipopolysaccharide from a rough strain of Ochrobactrum anthropi containing a 2,3-diamino-2,3-dideoxy-D-glucose disaccharide lipid A backbone

A degradation protocol using de-O-acylation and subsequent alkaline de-N-acylation was applied to the lipopolysaccharide of Ochrobactrum anthropi rough strain LMG 3301. Three main oligosaccharide bisphosphates containing core-lipid A backbone structures were obtained after fractionation by anion-exchange HPLC. Using 1H and 13C NMR spectroscopy, including two-dimensional COSY, TOCSY, and NOE spectroscopy (ROESY and NOESY), the following structures were established: [formula: see text] where Kdo is 3-deoxy-D-manno-octulosonic acid, D-GlcN3N is 2,3-diamino-2,3-dideoxy-D- glucose and R is H or alpha-D-GalpA or 4-deoxy-beta-L-threo-hex-4-enopyranuronic acid, the latter sugar being derived from alpha-D-GalpA by beta-elimination of a substituent attached to 0-4. This is the first report on the isolation from a lipopolysaccharide of an oligosaccharide containing GlcN3N in the lipid A backbone [beta-D-GlcpN3N4P-(1-->6)-alpha-D-GlcpN3N1 P]. Sugar and methylation analysis confirmed the presence of the GalA-->Kdo disaccharide and non-stoichiometric substitution of GalA. It is suggested that Glc is the substituent at 0-4 in GalA and that in the non-degraded lipopolysaccharide the amino group of GlcN is not acylated.     

A note on the stability of habituating process control

For a class of single-output processes with at least two control inputs, this note proposes a simple control design and study its stability. To this end, the process is factorized into a stable and non-minimum-phase factor and a possible unstable minimum-phase factor. By the addition of a (low-pass) filter of suitable dimension, one can obtain a process factorization where the minimum-phase factor has a proper and stable inverse. Once the plant has been factorized in this form, the proposed control synthesis method is composed of two main steps; namely, output regulation based on the non-minimum-phase factor and design of an optimization-based divider to compute the value corresponding to the multiple inputs. In this way, one obtains the control transfer function of each control input in a parallel control architecture. An analysis of the control structure is provided, giving sufficient conditions for the stability of the control loop.     

The use of packaging techniques to maintain freshness in fresh-cut fruits and vegetables: a review

Browning and other discolourations, softening, surface dehydration, water loss, translucency, off-flavour and off-odour development, as well as microbial spoilage are some of the most frequent causes of quality loss in fresh-cut products. Nowadays, the use of innovative modified atmospheres and edible coatings stands out among other techniques in the struggle for maintaining freshness and safety of fresh-cut fruits and vegetables. A few studies have demonstrated the effectiveness of these techniques when applied to different fresh-cut commodities. However, treatment and storage conditions for fresh-cut fruits are still being largely explored to better keep their fresh-like quality attributes. This review discusses the recent advances in the use of innovative modified atmosphere packaging (MAP) systems to maintain freshness of fresh-cut fruits and vegetables. Furthermore, special attention is devoted to the development of coatings that can be used as a complement or alternative to MAP.     

Hydrous oxide formation on gold in base under potential cycling conditions

The formation of hydrous oxide films on gold in base under potential cycling conditions was investigated and found to be less inhibited than the same type of reaction observed when gold is strongly anodized at high potentials under d.c. conditions at high pH. The overall behaviour on cycling is quite similar to that observed with other metals, e.g. platinum. The importance of the lower limit, for instance, again appears to be related to the need under film thickening conditions to significantly reduce the compact oxide layer formed on the metal surface during the anodic sweep. It was noted that the earlier duplex model for this type of system, i.e. an inner compact and an outer dispersed oxide layer, is not always valid. Under certain conditions about six distinct peaks (suggesting six different states of gold oxide hydration, dispersion or polymerization) were observed in cathodic sweeps recorded for the reduction of thick films grown on gold under potential cycling conditions in base.