Calixarene-based langmuir monolayers : from crystallization templates to metal organic networks

Molecular self-assembly plays a pivotal role in biological processes and living organisms can be considered as the result of the self-assembly of discrete molecular building blocks into sophisticated functional structures. Biology provides countless examples of complex and functional hierarchical self-assembled structures ranging from protein and nucleic acid biosynthesis to biological membranes self-assembly. Although Nature may produce such structures with an extreme efficieny, man-made chemical strategies to produce large covalent architectures are typically more complex and tedious. Due to the difficulty to precisely control the formation of large macromolecular architecture through covalent synthetic strategies, the self-assembly approach has been extensively exploited for the creation of supramolecular entities. Amphiphiles are compounds able to self-assemble in myriad supramolecular structures such as micelles, vesicles, nanosheets, nanorods, nanotubes and nanofibers, to name but a few. The shape of the resulting supramolecular assembly is dependent on the structure of the amphiphilic building block and type of solvent. Among all kinds of natural and synthetic amphiphiles, macrocyclic amphiphiles are of particular interest due to the possibility to conveniently control the hydrophilic/lipophilic balance of the final amphiphilic structure. The basket-like rigid conformation of calix[4]arenes, and the possibility to selectively functionalize both the upper and lower rim, make these molecules attractive building blocks for the design of amphiphilic compounds. Amphiphilic calix[4]arenes that are essentially insoluble in water self-assemble as monomolecular films at the air-water interface, forming Langmuir monolayers, where the aliphatic chains point into air while the polar functions are immerged into the subphase. Langmuir monolayers of amphiphilic calix[4]arene derivatives have been demonstrated to interact with a wide range of solutes, ranging from ions to macromolecules. In addition to this, calix[4]arene-based monolayers have been shown to induce the interfacial crystallization of inorganic and organic solids. The polar heads of the macrocycles act as recognition units for the interfacial nucleation of the to-be-crystallized molecules. Electrostatic interactions, along with geometrical complementarity between the macrocycles polar functions and the solute are the determining factors for the interfacial crystal growth. In this thesis, the ability of Langmuir monolayers of a p-carboxycalix[4]arene derivative to act as templates for the crystallization of gabapentin (GBP), an active pharmaceutical ingredient used to relieve neuropathic pain, with a control over its polymorphism is reported. The suitable chemical modification of the upper and lower rim of calix[4]arenes allows producing stable amphiphilic macrocycles able to form stable Langmuir monolayers at the air-water interface with strong affinities towards ions. The affinity of calix[4]arene-based Langmuir monolayers towards ions is mainly owing to the presence of a cavity that allows for the encapsulation of the ions, coupled with multiple polar ligating functions at the p-positions that strongly interact with the solute. In this thesis, the recognition properties of Langmuir monolayers of a series of p-carboxy- and p-aminocalix[4]arene derivatives towards strong, i.e. CuCl2, CoCl2, NiCl2 and MnCl2, and weak, i.e. HgCl2, electrolytes are reported. The effect of the inorganic compounds on the self-assembly properties of the calix[4]arene-based Langmuir monolayers is investigated by means of surface pressure-area compression isotherms, Brewster angle microscopy (BAM) and synchrotron-based X-ray diffraction techniques. Notably, it has been demonstrated that the structure of the macrocycle has a crucial effect on its interfacial organization. Upon interaction of a long chain, i.e. C12, p-carboxycalix[4]arene derivative with Cu2+ ions at the air-water interface, the corresponding calix[4]arene-based monolayer is mainly amorphous. On the other hand, Langmuir monolayers of the short chain (C3), structural analogue on aqueous Cu2+ ions subphases possess significantly large and highly ordered structures. It is assumed that the interfacial self-assembly of the long chain p-carboxycalix[4]arene derivative is mainly driven by van der Waals interactions among the aliphatic chains, which contribute to the partial disordered monolayer structure. On the contrary, the self-assembly of the short chain p-carboxycalix[4]arene derivative is driven by π-π interactions among aromatic rings of neighboring amphiphiles, which contribute to the highly ordered structure of the monomolecular film

Functional fish: improving nutrition for the elderly

Elder people need highly digestible foods that can also provide health benefits even to those suffering from chronic diseases. Furthermore, such foods should be palatable as well as familiar for elder consumers. Fish is a high-protein, low-fat food that potentially provides a range of health promoting effects which may be further improved with suitable approaches in the production systems. The present mini-review intends to report possible aquaculture interventions to enhance the positive impact of fish on elder health and to promote its function in terms of prevention and recovery of specific diseases. Some fish species during their lifespan experience periods of food restrictions that can be mimicked in aquaculture without affecting fish welfare. Under these circumstances fish can modify the fatty acid profile and increase the use of muscle proteins to fulfill their energy requirements, by activation of muscle endogenous proteases. Degradation of muscle proteins can enhance their digestibility and possibly the release of encrypted bioactive peptides, showing a plethora of biological actions, including the antihypertensive activity. The degree of myofibrillar protein degradation and the fatty acid profile of fish fillet can then be managed by suitable and sustainable feeding protocols in the context of farming conditions

Polymorphism control of an active pharmaceutical ingredient beneath calixarene-based Langmuir monolayers

This communication demonstrates the possibility to nucleate and grow different crystalline polymorphic forms of gabapentin (GBP) using

Coordination-Driven Monolayer-to-Bilayer Transition in 2D Metal-Organic Networks

We report on monolayer-to-bilayer transitions in 2D metal−organic networks (MONs) from amphiphiles supported at the water−air interface. Functionalized calix[4]arenes are assembled through the coordination of selected transition metal ions to yield monomolecular 2D crystalline layers. In the presence of Ni(II) ions, interfacial self-assembly and coordination yields stable monolayers. Cu(II) promotes 2D coordination of a monolayer which is then diffusively reorganizing, nucleates, and grows a progressive amount of second layer islands. Atomic force microscopic data of these layers after transfer onto solid substrates reveal crystalline packing geometries with submolecular resolution as they are varying in function of the building blocks and the kinetics of the assembly. We assign this monolayer-to- bilayer transition to a diffusive reorganization of the initial monolayers owing to chemical vacancies of the predominant coordination motif formed by Cu2+ ions. Our results introduce a new dimension into the controlled monolayer-to-multilayer architecturing of 2D metal− organic networks

Chemical composition and apparent digestibility of a panel of dried microalgae and cyanobacteria biomasses in rainbow trout (Oncorhynchus mykiss)

Despite a growing interest in microalgae and cyanobacteria as potential sources of nutrients in aquafeeds, little information is presently available on their nutritive value for carnivorous fish species. The aim of this study was to evaluate chemical composition and nutrient digestibility of a panel of microalgae and cyanobacteria dried biomasses (MACB), using rainbow trout (Oncorhynchus mykiss W.) as a fish model. Nine test diets were obtained by mixing 80 parts of a reference diet, added with 20 g/kg of acid insoluble ash as an indigestible marker, to 20 parts of each of the following dried whole-cell biomass: Arthrospira platensis, Nostoc sphaeroides, two strains of Chlorella sorokiniana, Nannochloropsis oceanica, Tisochrysis lutea, Phaeodactylum tricornutum, Porphyridium purpureum and Tetraselmis suecica. The digestibility measurements were conducted with rainbow trout (52.4 \ub1 1.5 g) kept in six tank units each including three 60-L vessels singularly stocked with 12 fish and fitted with a settling column for faecal recovery. Per each diet, faeces were collected over three independent 10-day periods. Apparent digestibility coefficients (ADCs) of dry matter, crude protein (CP), organic matter and gross energy (GE) of single MACB were calculated by difference relative to those of the reference diet. The MACBs had heterogeneous chemical composition (CP, from 20 to 69%; Lipid, 5\u201327%; GE, 12.5-\u201322.6 MJ/kg dry matter basis) reflecting their overall biodiversity. Most of them can be considered as virtually good sources of minerals and trace elements and exhibit an essential amino acid profile comparable or even better than that of soybean meal commonly used in fish feeds with P. purpureum showing the best protein profile. The digestibility results obtained with rainbow trout allowed ranking the MACBs into two major groups. A first one, including C. sorokiniana, N. oceanica and T. suecica, resulted in markedly lower (P < 0.05) crude protein and energy ADC (64\u201373%; 51\u201359%, respectively) compared to a second group including P. purpureum, T. lutea and cyanobacteria (CP-ADC, 83\u201388%; GE-ADC, 74\u201390%) while P. tricornutum resulted in intermediate values. Overall, the present study confirms the consistently reported role of cell-wall structure/composition in affecting accessibility of nutrients to digestive enzyme. Based on the overall outcomes, only T. lutea and cyanobacteria actually meet the requirements for being used as protein sources in aquafeeds provided their mass production becomes more feasible and costeffective, hence attractive for the feed-mill industry in the near future

The use of stable isotope ratio analysis to trace European sea bass (D. labrax) originating from different farming systems

This study aimed to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems and geographic origins. Dicentrarchus labrax of commercial size from three different rearing systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) were collected at the trading period (autumn\u2013winter). For each farming type, different locations spread over Italy were monitored. Once the fish were harvested, the muscle and feed were sampled. For both muscle and feed, \u3b413C and \u3b415N were measured by continuous flow elemental analyzer isotope ratio mass spectrometry (CF-EA-IRMS) with the goal of discriminating samples based on the rearing system. Additional \u3b42H and \u3b418O measurements of fish samples were performed by continuous flow total combustion elemental analyzer isotope ratio mass spectrometry (CF-TC/EA-IRMS) to track the geographical origin. The measurements of \u3b413C and \u3b415N made it possible to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Additional information was obtained from \u3b418O and \u3b42H, which enabled the geographical areas of origin of the sea bass farmed extensively and intensively (in cages) to be distinguished

Replacing maize grain with ancient wheat lines by‐products in organic laying hens’ diet affects intestinal morphology and enzymatic activity

The effects of replacement of maize grain with ancient wheat by‐products on intestinal morphometry and enzymatic activity in laying hens was studied. Eighty hens were divided into two groups (40 each, 8 replicates, 5 hens/replicate) fed two isoproteic and isoenergetic diets. In the treated group, part of the maize was replaced by a mix of ancient grains (AGs) middling, in a 50:50 ratio of Triticum aestivum L. var. spelta (spelt) and Triticum durum dicoccum L. (emmer wheat). The AG diet affected the weight of all the large intestine tracts, decreasing the weight of caeca (p < 0.01) and increasing those of colon (p < 0.01), rectum and cloaca (p < 0.05). Villus height in the AG group was higher (p < 0.01) than the control for the duodenum and jejunum, while for the ileum, the control group showed the highest values (p < 0.01). The submucosa thickness was higher (p < 0.01) in the control group for the duodenum and ileum, while the jejunum for the AG group showed the highest (p < 0.05) submucosa thickness. The crypts depth was higher (p < 0.01) in the control group for the duodenum and ileum. Enzyme activity was enhanced by AGs (p < 0.01) in the duodenum. Regarding the jejunum, sucrase‐isomaltase and alkaline phosphatase had higher activity (p < 0.05 and p < 0.01, respectively) in the AG group. In the ileum, sucrase‐isomaltase showed higher activity (p < 0.01) in the control group, while alkaline phosphatase showed the highest values (p < 0.05) in the AG group. Overall, results suggested that the dietary inclusion of AGs exerted positive effects in hens, showing an improved intestinal function

Functional infrared imaging of paroxysmal ischemic events in patients with Raynaud's phenomenon.

The use of thermal infrared (IR) imaging together with the study of the thermal recovery from a controlled cold challenge has been proposed in the diagnosis and follow-up of therapeutic response of Raynaud's Phenomenon (RP) and Systemic Sclerosis (SSc). The controlled cold challenge test usually performed during IR investigations may induce a RP in patients with the latter condition. In our Institution we routinely perform capillaroscopy and thermal IR to follow-up SSc patients. In this paper, we describe the thermal recovery patterns shown by two SSc patients (a 40 year-old male with diffuse variant of SSc and a 71 year-old female with a limited variant of SSc) who presented ischemic and paroxysmal RP attack while recovering from the routine controlled cold challenge test. During RP attack, the cutaneous temperature of some fingers continued to decrease for some minutes even after the cessation of the cold stress. To the best of our knowledge, to date, no literature report has documented the thermal behaviour of SSc patients' fingers which occasionally present ischemic and paroxysmal response. Triggering of ischemic RP attack appears to not rely only on morphological and structural finger impairment, but also upon other aspects, like the emotional attitude of the subject and the possible discomfort experienced with the proceeding of the functional cold stress test