Janus particles by simplified RAFT-based emulsion polymerization process for polymer coating

We describe a simplified method to synthesize film forming polymer Janus particles by phase separation during RAFT-based free radical emulsion polymerization. Fully crosslinked snowman- or football-shaped polystyrene Janus particles (PSJPs) were first produced in a one-step batch process using amphiphilic triblock macro-RAFT copolymers as stabilizers. Such particles were in turn employed as seeds in a continuous emulsion polymerization in which a monomer mixture of methyl methacrylate (MMA) and butyl acrylate (BA) (1/1 by weight) was constantly injected into the reaction in the presence of a water soluble initiator. The added monomers wetted seed particle surface and their polymerization led to formations of 93-nm film forming single- or two-headed Janus particles. The resulted latex was successfully used to disperse and encapsulate solid calcite extender. Graphical abstract

Assessment of the influence of the structural characteristics of granular systems of microsilicon on the properties of thermal insulation materials

The article discusses experimental studies of the size and shape of structured particles of microsilica small angle x-ray scattering method and a photophonon theoretical description of the heat transfer process in complex heterogeneous structures to assessment of the structural characteristics of granular systems for the properties of thermal insulating materials. The mechanism of heat transfer in granular, porous systems is quite complex, since heat exchange occurs in a material consisting of two phases (solid and gas) and at the phase boundary. Heat transfer in liquid thermal insulation coatings can be carried out from one solid particle to another. In this case, the thermal conductivity will depend on: the chemical and elemental composition of the material; particle granulometry; surface topology - the presence of inhomogeneities, defects on the surface; the number of touches and the contact area between the particles. The heat transfer of gas in the pores is carried out when gas molecules collide. Thermal conductivity will be determined by the ratio of the free path of molecules and linear pore sizes, temperature and dynamic viscosity of the gas phase, the nature of the interaction of gas molecules with the solid phase. Heat transfer by radiation depends on the nature of the particles, the dielectric, magnetic permeability and the degree of blackness of the particle surface. Based on the analysis of possible mechanisms of heat transfer in granular systems, it can be argued that the effective thermal conductivity of the system depends, all other things being equal, on the structure of the pore space of granular materials, topology and the number of particle touches. Considering idealized models of the structure of granular materials in the form of ordered folds of perfectly smooth balls, we can obtain several variants of structures: with tetrahedral; hexagonal; cubic packing of balls.

Interface topology and evolution of particle patterns on deformable drops in turbulence

The capture of neutrally buoyant, sub-Kolmogorov particles at the interface of deformable drops in turbulent flow and the subsequent evolution of particle surface distribution are investigated. Direct numerical simulation of turbulence, phase-field modelling of the drop interface dynamics and Lagrangian particle tracking are used. Particle distribution is obtained considering excluded-volume interactions, i.e. by enforcing particle collisions. Particles are initially dispersed in the carrier flow and are driven in time towards the surface of the drops by jet-like turbulent fluid motions. Once captured by the interfacial forces, particles disperse on the surface. Excluded-volume interactions bring particles into long-term trapping regions where the average surface velocity divergence sampled by the particles is zero. These regions correlate well with portions of the interface characterized by higher-than-mean curvature, indicating that modifications of the surface tension induced by the presence of very small particles will be stronger in the highly convex regions of the interface.

The Influence of Silica Nanoparticles Geometry on the Interfacial Interactions of Organic Molecules: A Simulation Perspective

The role of nanoparticle shape in the interaction and adsorption of organic molecules on the particle surface is an unexplored area. On the other hand, such knowledge is not only...

Sodium Caseinate and Acetylated Mung Bean Starch for the Encapsulation of Lutein: Enhanced Solubility and Stability of Lutein

Lutein is a kind of vital carotenoid with high safety and significant advantages in biological functions. However, poor water solubility and stability of lutein have limited its application. This study selected different weight ratios of sodium caseinate to acetylated mung bean starch (10:0, 9:1, 7:3, 5:5, 3:7, 1:9, and 0:10) to prepare lutein emulsions, and the microcapsules were produced by spray drying technology. The microstructure, physicochemical properties, and storage stability of microcapsules were investigated. The results show that the emulsion systems were typical non-Newtonian fluids. Lutein microcapsules were light yellow fine powder with smooth and relatively complete particle surface. The increase of sodium caseinate content led to the enhanced emulsion effect of the emulsion and the yield and solubility of microcapsules increased, and wettability and the average particle size became smaller. The encapsulation efficiency of lutein microcapsules ranged from 69.72% to 89.44%. The thermal characteristics analysis showed that the endothermic transition of lutein microcapsules occurred at about 125 °C. The microcapsules with sodium caseinate as single wall material had the worst stability. Thus, it provides a reference for expanding the application of lutein in food, biological, pharmaceutical, and other industries and improving the stability and water dispersion of other lipid-soluble active ingredients.

Efficient Delivery of Hydrophilic Small Molecules to Retinal Cell Lines Using Gel Core-Containing Solid Lipid Nanoparticles

In this study, we developed a novel solid lipid nanoparticle (SLN) formulation for drug delivery of small hydrophilic cargos to the retina. The new formulation, based on a gel core and composite shell, allowed up to two-fold increase in the encapsulation efficiency. The type of hydrophobic polyester used in the composite shell mixture affected the particle surface charge, colloidal stability, and cell internalization profile. We validated SLNs as a drug delivery system by performing the encapsulation of a hydrophilic neuroprotective cyclic guanosine monophosphate analog, previously demonstrated to hold retinoprotective properties, and the best formulation resulted in particles with a size of ±250 nm, anionic charge > −20 mV, and an encapsulation efficiency of ±60%, criteria that are suitable for retinal delivery. In vitro studies using the ARPE-19 and 661W retinal cell lines revealed the relatively low toxicity of SLNs, even when a high particle concentration was used. More importantly, SLN could be taken up by the cells and the release of the hydrophilic cargo in the cytoplasm was visually demonstrated. These findings suggest that the newly developed SLN with a gel core and composite polymer/lipid shell holds all the characteristics suitable for the drug delivery of small hydrophilic active molecules into retinal cells.

A Nanogel with Effective Blood-Brain Barrier Penetration Ability through Passive and Active Dual-Targeting Function

Clinically, surgery assisted by chemotherapy is the most effective treatment of cancer. But from our clinical observation, the median survival of patients with glioblastoma is still not so good with only 15-16 months. The low therapeutic index is mainly due to the blood-brain barrier (BBB) which significantly hindered the chemotherapeutic drug accumulation in tumor tissue. One main composition of the BBB is astrocyte, which contains a lipophilic cell membrane, which prevents more than 98% of small-molecule drugs from entering the brain. Previously, we found that the nanogel with passive targeting function can increase the BBB penetration ability, which indicates that it could be used to overcome the above mentioned in vivo obstacles which promoted drug accumulation in the tumor. In this study, thermosensitive targeted nanogel delivery systems (DPPC) with cell-penetrating peptides (CPP) are introduced onto the particle surface for active astrocyte breaking. The hydrodynamic radius of DPPC is around 300 nm, the potential is about 0-5 mV, and the TEM and DLS studies further confirm its well spherical morphology and uniform distribution. The DPPC is verified as the biocompatible carriers for further application by cell viability tests. The in vitro-constructed BBB model successfully proves that DPPC can efficiently penetrate the BBB, which is attributed to both the temperature-sensitive passive targeting and the active CPP penetration. Consequently, the intracellular doxorubicin (DOX) promotes such functional DPPC at the relatively high temperature inside tumor microenvironment (TME) (~42°C), which obviously improves intratumor drug accumulation and tumor cell-killing effects. The dual-targeted nanogel delivery systems designed in this study provides a more effective strategy for the treatment of glioma.

Record-breaking stratospheric smoke and record-breaking ozone depletion events in the Arctic and in Antarctica in 2020! Any link between smoke occurrence and ozone depletion?

<p>The highlight of our multiwavelength polarization Raman lidar measurements during the 1-year MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the Arctic Ocean ice from October 2019 to May 2020 was the detection of a persistent, 10 km deep aerosol layer in the upper troposphere and lower stratosphere (UTLS) with clear and unambiguous wild-fire smoke signatures. The smoke is supposed to originate from extraordinarily intense and long-lasting wildfires in central and eastern Siberia in July and August 2019 and may have reached the tropopause layer by the self-lifting process.</p><p>Temporally almost parallelly, record-breaking wildfires accompanied by unprecedentedly strong pyroconvection were raging in the south-eastern part of Australia in late December 2019 and early January 2020. These fires injected huge amounts of biomass-burning smoke into the stratosphere where the smoke particles became distributed over the entire southern hemispheric in the UTLS regime from 10-30 km to even 35 km height. The stratospheric smoke layer was monitored with our Raman lidar in Punta Arenas (53.2°S, 70.9°W, Chile, southern South America) for two years.</p><p>The fact that these two events in both hemispheres coincided with record-breaking ozone hole events in both hemispheres in the respective spring seasons motivated us to discuss a potential impact of the smoke particles on the strong ozone depletion. The discussion is based on the overlapping height ranges of the smoke particles, polar stratospheric clouds, and the ozone hole regions. It is well known that strong ozone reduction is linked to the development of a strong and long-lasting polar vortex, which favours increased PSC formation. In these clouds, active chlorine components are produced via heterogeneous chemical processes on the surface of the PSC particles. Finally, the chlorine species destroy ozone molecules in the spring season. However, there are two pathways to influence ozone depletion by aerosol pollution. The particles can influence the evolution of PSCs and specifically their microphysical properties (number concentration and size distribution), and on the other hand, the particles can be directly involved in heterogeneous chemical processes by increasing the particle surface area available to convert nonreactive chlorine components into reactive forms. A third (indirect) impact of smoke, when well distributed over large parts of the Northern or Southern hemispheres, is via the influence on large-scale atmospheric dynamics.</p><p>We will show our long-term smoke lidar observations in the central Arctic and in Punta Arenas as well as ozone profile measurements during the ozone-depletion seasons. Based on these aerosol and ozone profile data we will discuss the potential interaction between smoke and ozone.</p>