Surface energy analysis (SEA) and rheology of powder milk dairy products

Results of inverse gas chromatography adsorption/desorption experiments using selected probes on skimmed milk, whey and demineralised whey powder materials are presented. The dispersive component of surface energy was found to be dominant, indicating a low polarity character. Surface energy profiles of demineralised whey and skimmed milk showed a characteristic steep exponential decrease from approximately 170 mJ/m2 to 60 mJ/m2 and 140 mJ/m2 to 45 mJ/m2, respectively, whereas whey powder exhibited a constant (non-exponential) surface energy at approximately 45 mJ/m2. The dispersive surface energy of demineralised whey and skimmed milk powder showed a broad distribution ranging from 40 mJ/m2 to 120 mJ/m2 and 175 mJ/m2, respectively. In contrast, the dispersive surface energy distribution for whey was very narrow, ranging from only 42.8 mJ/m2 to 45 mJ/m2. The determined yield locus and Mohr's circles indicated that demineralised whey exhibited free flowing powder characteristics, whereas skimmed milk and whey exhibited cohesive powder flow behaviour

Coordination effects on the binding of late 3d single metal species to cyanographene

Anchoring single metal atoms on suitable substrates is a convenient route towards materials with unique electronic and magnetic properties exploitable in a wide range of applications including sensors, data storage, and single atom catalysis (SAC). Among a large portfolio of available substrates, carbon-based materials derived from graphene and its derivatives have received growing concern due to their high affinity to metals combined with biocompatibility, low toxicity, and accessibility. Cyanographene (GCN) as highly functionalized graphene containing homogeneously distributed nitrile groups perpendicular to the surface offers exceptionally favourable arrangement for anchoring metal atoms enabling efficient charge exchange between the metal and the substrate. However, the binding characteristics of metal species can be significantly affected by the coordination effects. Here we employed density functional theory (DFT) calculations to analyse the role of coordination in the binding of late 3d cations (Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Cu+, and Zn2+) to GCN in aqueous solutions. The inspection of several plausible coordination types revealed the most favourable arrangements. Among the studied species, copper cations were found to be the most tightly bonded to GCN, which was also confirmed by the X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and isothermal titration calorimetry (ITC) measurements. In general, the inclusion of coordination effects significantly reduced the binding affinities predicted by implicit solvation models. Clearly, to build-up reliable models of SAC architectures in the environments enabling the formation of a coordination sphere, such effects need to be properly taken into account.Web of Science25129628

Surface energy analysis (SEA) study of hyaluronan powders

Results of inverse gas chromatography adsorption/desorption experiments of selected probes on sodium hyaluronate powder material are presented. It was found that a dominating was a dispersive surface energy part thus indicating low polarity character of the studied HA powder. For 0% coverage 30mJ/m2 total surface energy was found. There was found a relatively high inhomogeneity of the surface structure of the studied polymer powder. A total surface energy distribution was ranging from 10 to 34mJ/m2 with maximum at 18.5mJ/m2. It was similarly as in the previous case of surface energy profile controlled by dispersive part. By measuring free energy profiles dependencies for selected probe molecules of different polarity there was found approximately seven-fold higher energy content (15kJ/mol) in comparison to dichloromethane (2kJ/mol). There were determined work of cohesion and work of adhesion (water) on HA surface. © 2013 Elsevier B.V

Physicochemical analysis of hyaluronic acid powder for cosmetic and pharmaceutical processing

Hyaluronic acid (HA) is found in extracellular tissue in many parts of the body. It is a material of increasing importance to biomaterials science and is finding applications in diverse areas ranging from tissue culture scaffolds to cosmetic materials. Its properties, both physical and biochemical, in solution or hydrogel form, are extremely attractive for various technologies concerned with body repair. This book considers the materials science behind some of the important biomedical and therapeutic applications that are emerging for HA. Key characteristics such as its mechanical properties, biological function and degradation are discussed. The latest technologies in chemical modification and crosslinking strategies are analysed and emerging applications in soft and hard tissue repair are highlighted. The first objective of the book, which consists of a collection of chapters from leading researchers across the globe, is to highlight the role of HA based hydrogels as scaffolds in sustaining stem cells for transplantation and regrowth. The second objective is to detail the significant influence of HA derived materials in the latest advances in cancer therapy, general therapeutics and cosmetics. The third objective is to link the structure-property relationships of HA to medical function and application while reflecting on current clinical and market trends. The book will be of interest to those involved in HA research for medical device and therapeutic applications. Graduate and undergraduate students engaged in the fields of biomedical engineering, materials science, chemistry, medical science, pharmaceutical science and polymer science will find this book of particular interest.I, P(ED2.1.00/03.0058

I. SELF RECOGNITION BY T CELLS Bystander Killing of Target Cells Bearing Syngeneic MHC Antigens

T cell activation is restricted in the sense that T cells respond to antigens only in the context of self MHC antigens (1). It has been shown (2-4) that T cells learn about self in the thymus but the unanswered question is, how. Approximately 95% of the cells in the thymus die in situ (5, 6). To account for the low survival rate, and forMHC restriction, it has been proposed that the majority of immature thymocytes, whose receptors have little or no affinity for self MHC, do not receive the proper maturational signals and undergo programmed cell death (7, 8). Cells that are strongly self-reactive are deleted (9-12). The small proportion ofthymocytes whose receptors have the "right " affinity (low but real) for selfMHC antigens are positively selected to survive and are exported to the periphery. These cells would bind weakly to self alone, but they might bind strongly, that is, with activating affinity, to self plus antigenic peptides (13). This model predicts that all mature T cells should be able to recognize the selecting self-MHC molecules. However, the binding ofT cells with cells bearing selfMHC in the absence of specific antigen cannot, by definition, result in activation. With this limitation in mind can we determine if selfrecognitio

Surface heterogeneity: Information from inverse gas chromatography and application to model pharmaceutical substances

The general theory of electrokinetic phenomena strictly applies to ideal and rigid surfaces or particles. However, many interfaces are non-ideal with respect to both the surface smoothness and surface homogeneity. Detailed knowledge and understanding of the interface structure is often required for proper analysis of electrokinetic measurements. In this study, we investigate the option of studying surface heterogeneity using powder polycrystalline active pharmaceutical ingredients (APIs) as our model systems. We characterized these by a combination of physicochemical techniques, i.e. inverse gas chromatography surface energy analysis, SEM, thermal analysis and powder rheology, to assess the surface interface structure, topology, roughness, chemical heterogeneity and cooperative macroscopic behaviour. The latter characteristics are reflected in the three dimensional packing, which, in turn, affects the porosity and rigidity of the obtained powder bed. Such information is also of paramount interest for realizing proper fluid transport and dispersing or tableting API substances in the pharmaceutical industry. Notably, the 3D packing is affected not only by geometrical characteristics of the powders but also by the polarity and surface charge distribution. These characteristics can be correlated with surface energy data by means of surface energy profiles and surface energy distribution plots. © 2016 Elsevier LtdTeva Czech Industries; Ministry of Education, Youth and Sports of the Czech Republic [LO1305

Hierarchical porous metal-organic framework materials for efficient oil-water separation

Oil contaminated water is a global issue, decreasing the quality of water sources and is posing a threat to the health of humans and many ecosystems. The utilization of industrial level strategies is limited mainly due to their complex and time-consuming processing. Considering this, we choose materials for separating oils from water based on their ease of handling and good performance. However, high surface area porous materials, such as linens, zeolites, cotton, etc., offer low efficiency for oil/water separation. Special wettability is the most promising property of materials and is helpful for oil-water separation. Metal-organic frameworks (MOFs), a class of highly tunable porous structures of metal clusters/ions and multidentate organic ligands, offer exciting prospects for various applications. The unique tunability of the structure and properties of these materials can endow them with special wettability for the treatment of oily water. This review focuses on hydrophobic-oleophilic, hydrophilic-underwater oleophobic and switchable wettability MOFs and their implementation as oil/water separating materials. We classify different MOF-based materials as filtration materials, absorbents or adsorbents based on the methodology they are used in for separating oil/water mixtures and emulsions. We discuss different subclasses of MOF-based filtration, absorbent and adsorbent materials and summarize recent developments in their oil/water separation applications. Finally, we end our discussion by critically analyzing the importance of these MOFs for separating oils from water and highlighting potential future directions for achieving improved performance.Web of Science1062785275

Molecular insights from theoretical calculations explain the differences in affinity and diffusion of airborne contaminants on surfaces of hBN and graphene

Exposed surfaces of two-dimensional (2D) materials are susceptible to the adsorption of various molecules including airborne contaminants, which can affect their performance in real applications. Hexagonal boron nitride (hBN) is structurally the closest relative to graphite and its single layer form to graphene. The adsorption of organic molecules to graphene was subject of extensive research, however, little is known about interaction of adsorbates to hBN surface. We studied the affinity of organic molecules to the surface of hBN by inverse gas chromatography. The adsorption enthalpies of polar molecules including acetonitrile, nitromethane, ethanol, and acetone exhibited strong coverage dependency up to 20 % of a monolayer. Density functional theory and molecular dynamics calculations were employed to understand and interpret experimentally measured adsorption enthalpies. The calculations revealed that the strong affinity of polar molecules at low coverage was due to adsorption on steps and edges of hBN. The calculated surface diffusion barriers of all molecules were rather low, i.e., below 0.5 kcal/mol (except for benzene and cyclohexane), and molecules adsorbed on the surface behaved like a 2D gas. The results demonstrated that coupling inverse gas chromatography with computer simulations can provide vital insights into the mechanism of adsorption at the molecular level.Web of Science565art. no. 15038