There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Colloidal particles act in many ways like surfactant molecules, particularly if adsorbed to a fluid–fluid interface. Just as the water or oil-liking tendency of a surfactant is quantified in terms of the hydrophile–lipophile balance (HLB) number, so can that of a spherical particle be described in terms of its wettability via contact angle. Important differences exist, however, between the two types of surface-active material, due in part to the fact that particles are strongly held at interfaces. This review attempts to correlate the behaviour observed in systems containing either particles or surfactant molecules in the areas of adsorption to interfaces, partitioning between phases and solid-stabilised emulsions and foams.

Particles as surfactants—similarities and differences

基礎講座 電気泳動(Electrophoresis)

Intermolecular And Surface Forces

Zein–curcumin composite colloidal particles were synthesized using an antisolvent precipitation method The average particle size could be controlled down to 100–150 nm, depending on the solvent system and the ratio of zein and curcumin used in the synthesis In all cases, spherical particles were obtained, as confirmed by transmission electron microscopy Depending on the preparation conditions, curcumin load and encapsulation efficiency varied from 16 to 41% and 711 to 868%, respectively Solid state characterization by differential scanning calorimetry and X-ray diffraction indicated the amorphous nature of entrapped curcumin An UV irradiation study confirmed enhanced photostability of curcumin due to the entrapment of curcumin in the biopolymeric matrix The particles were also found to have good colloidal stability at a broad range of physiologically relevant pH (12, 45, 67 and 74) and in simulated gastro-intestinal conditions Results from an in vitro mucoadhesion study showed retention of more than 60% curcumin for 150 minutes The mucoadhesion property was further confirmed from a mucin association study carried out on Caco-2 cells

Synthesis and characterisation of zein–curcumin colloidal particles

Few fully natural and biocompatible materials are available for the effective particle-stabilization of emulsions since strict requirements, such as insolubility in both fluid phases and intermediate wettability, need to be met. In this paper, we demonstrate the first use of water-insoluble proteins, employing the corn protein zein as a representative of this family, as effective particle-stabilizers of oil-in-water emulsions of natural oils and water. For this purpose, we synthesized zein colloidal particles through an anti-solvent precipitation procedure and demonstrated their use in the formation of stable oil-in-water Pickering emulsions as a function of particle concentration, pH and ionic strength. We confirmed that the wetting properties of zein, studied as a function of pH and ionic strength, strongly favor interfacial particle adsorption with oil-in-water three-phase contact angles θow close to 90°. We found that unmodified zein colloidal particles can produce stable, surfactant-free o/w emulsions with droplet sizes in the range 10–200 μm under experimental mixing conditions (2 min with Ultra Turrax homogenizer at 13500 rpm) at pH above and below the isoelectric point of zein, for low to moderate ionic strengths (1–10 mM). Under conditions where the particle volume fraction is low (<0.2 wt%) or at low pH, the resulting emulsions are not stable against coalescence. At a higher ionic strength, the zein particles have a tendency to aggregate and the resulting emulsions flocculate, forming an emulsion–gel phase.

Oil-in-water Pickering emulsions stabilized by colloidal particles from the water-insoluble protein zein

The focus in the study of Pickering foams and emulsions has recently been shifting from using inorganic particles to adopting particles of biological origin for stabilization. This shift is motivated by the incompatibility of some inorganic particles for food and biomedical applications, as well as their poor sustainability. This review focuses on major developments in foams and emulsions stabilized by particles of biological origin from the last 5 years. Recent reports in the literature have demonstrated the ability of particles derived from cellulose, lignin, chitin, starch, proteins (soy, zein, ferritin), as well as hydrophobic cells to stabilize biphasic dispersions. We review the use of such nano- and micron-sized particles of biological origin for the stabilization of foams and emulsions, summarize the current knowledge of how such particles stabilize these dispersions, provide an outlook for future work to improve our understanding of bio-derived particle-stabilized foams and emulsions, and touch upon how these systems can be used to create novel materials.

/pdf/pickering-stabilization-of-foams-and-emulsions-with-43jar3wv67.pdf

Pickering stabilization of foams and emulsions with particles of biological origin

We report the growth of binary colloidal crystals with control over the crystal orientation through a simple layer-by-layer process. Well-ordered single binary colloidal crystals with a stoichiometry of large (L) and small (S) particles of LS2 and LS were generated. In addition, we observed the formation of an LS3 superstructure. The structures formed as a result of the templating effect of the first layer and the forces exerted by the surface tension of the drying liquid. By using spheres of different composition, one component can be selectively removed, as is demonstrated in the growth of a hexagonal non-close-packed colloidal crystal.

https://science.sciencemag.org/content/sci/296/5565/106.full.pdf

Layer-by-layer growth of binary colloidal crystals.

The formulation of micronutrients and nutraceuticals in the design of functional foods brings enormous technological challenges. The incorporation of micronutrients and/or nutraceuticals can compromise the product functionality. Issues often encountered are related to unwanted changes in the product physico-chemical stability, appearance, texture, flavour, taste and bioavailability due to inherited instability or interactions with other ingredients. This review intends to present the general strategies in using colloidal dispersions as delivery systems for micronutrients and nutraceuticals. Some illustrative examples will be given on how colloidal delivery systems can be utilised in the design of novel functional foods.

Krassimir P. Velikov

Papers

Synthesis and characterisation of zein–curcumin colloidal particles

Oil-in-water Pickering emulsions stabilized by colloidal particles from the water-insoluble protein zein

Pickering stabilization of foams and emulsions with particles of biological origin

Layer-by-layer growth of binary colloidal crystals.

Colloidal delivery systems for micronutrients and nutraceuticals