Simulations of microfluidic droplet formation using the two-phase level set method

Microdroplet formation is an emerging area of research due to its wide-ranging applications within microfluidic based lab-on-a-chip devices. Our goal is to understand the dynamics of droplet formation in a microfluidic T-junction in order to optimize the operation of the microfluidic device. Understanding of this process forms the basis of many potential applications: synthesis of new materials, formulation of products in pharmaceutical, cosmetics and food industries. The two-phase level set method, which is ideally suited for tracking the interfaces between two immiscible fluids, has been used to perform numerical simulations of droplet formation in a T-junction. Numerical predictions compare well with experimental observations. The influence of parameters such as flow rate ratio, capillary number, viscosity ratio and the interfacial tension between the two immiscible fluids is known to affect the physical processes of droplet generation. In this study the effects of surface wettability, which can be controlled by altering the contact angle, are investigated systematically. As competitive wetting between liquids in a two-phase flow can give rise to erratic flow patterns, it is often desirable to minimize this phenomenon as it can lead to a disruption of the regular production of uniform droplets. The numerical simulations predicted that wettability effects on droplet length are more prominent when the viscosity ratio λ (the quotient of the viscosity of the dispersed phase with the viscosity of the continuous phase) is O(1), compared to the situation when λ is O(0.1). The droplet size becomes independent of contact angle in the superhydrophobic regime for all capillary numbers. At a given value of interfacial tension, the droplet length is greater when λ is O(1) compared to the case when λ is O(0.1). The increase in droplet length with interfacial tension, σ, is a function of with the coefficients of the regression curves depending on the viscosity ratio.     

Primary Cilia Structure Is Prolonged in Enteric Neurons of 5xFAD Alzheimer’s Disease Model Mice

Neurodegenerative diseases such as Alzheimer’s disease (AD) have long been acknowledged as mere disorders of the central nervous system (CNS). However, in recent years the gut with its autonomous nervous system and the multitude of microbial commensals has come into focus. Changes in gut properties have been described in patients and animal disease models such as altered enzyme secretion or architecture of the enteric nervous system. The underlying cellular mechanisms have so far only been poorly investigated. An important organelle for integrating potentially toxic signals such as the AD characteristic A-beta peptide is the primary cilium. This microtubule-based signaling organelle regulates numerous cellular processes. Even though the role of primary cilia in a variety of developmental and disease processes has recently been recognized, the contribution of defective ciliary signaling to neurodegenerative diseases such as AD, however, has not been investigated in detail so far. The AD mouse model 5xFAD was used to analyze possible changes in gut functionality by organ bath measurement of peristalsis movement. Subsequently, we cultured primary enteric neurons from mutant mice and wild type littermate controls and assessed for cellular pathomechanisms. Neurite mass was quantified within transwell culturing experiments. Using a combination of different markers for the primary cilium, cilia number and length were determined using fluorescence microscopy. 5xFAD mice showed altered gut anatomy, motility, and neurite mass of enteric neurons. Moreover, primary cilia could be demonstrated on the surface of enteric neurons and exhibited an elongated phenotype in 5xFAD mice. In parallel, we observed reduced β-Catenin expression, a key signaling molecule that regulates Wnt signaling, which is regulated in part via ciliary associated mechanisms. Both results could be recapitulated via in vitro treatments of enteric neurons from wild type mice with A-beta. So far, only a few reports on the probable role of primary cilia in AD can be found. Here, we reveal for the first time an architectural altered phenotype of primary cilia in the enteric nervous system of AD model mice, elicited potentially by neurotoxic A-beta. Potential changes on the sub-organelle level—also in CNS-derived neurons—require further investigations.     

Sequence Features of Drosha and Dicer Cleavage Sites Affect the Complexity of IsomiRs

The deep-sequencing of small RNAs has revealed that different numbers and proportions of miRNA variants called isomiRs are formed from single miRNA genes and that this effect is attributable mainly to imprecise cleavage by Drosha and Dicer. Factors that influence the degree of cleavage precision of Drosha and Dicer are under investigation, and their identification may improve our understanding of the mechanisms by which cells modulate the regulatory potential of miRNAs. In this study, we focused on the sequences and structural determinants of Drosha and Dicer cleavage sites, which may explain the generation of homogeneous miRNAs (in which a single isomiR strongly predominates) as well as the generation of heterogeneous miRNAs. Using deep-sequencing data for small RNAs, we demonstrate that the generation of homogeneous miRNAs requires more sequence constraints at the cleavage sites than the formation of heterogeneous miRNAs. Additionally, our results indicate that specific Drosha cleavage sites have more sequence determinants in miRNA precursors than specific cleavage sites for Dicer and that secondary structural motifs in the miRNA precursors influence the precision of Dicer cleavage. Together, we present the sequence and structural features of Drosha and Dicer cleavage sites that influence the heterogeneity of the released miRNAs.     

From ELF to Compressibility in Solids

Understanding the electronic nature of materials’ compressibility has always been a major issue behind tabulation and rationalization of bulk moduli. This is especially because this understanding is one of the main approaches to the design and proposal of new materials with a desired (e.g., ultralow) compressibility. It is well recognized that the softest part of the solid will be the one responsible for its compression at the first place. In chemical terms, this means that the valence will suffer the main consequences of pressurization. It is desirable to understand this response to pressure in terms of the valence properties (charge, volume, etc.). One of the possible approaches is to consider models of electronic separability, such as the bond charge model (BCM), which provides insight into the cohesion of covalent crystals in analogy with the classical ionic model. However, this model relies on empirical parametrization of bond and lone pair properties. In this contribution, we have coupled electron localization function (ELF) ab initio data with the bond charge model developed by Parr in order to analyze solid state compressibility from first principles and moreover, to derive general trends and shed light upon superhard behavior.     

Quantitative Analysis of PMLA Nanoconjugate Components after Backbone Cleavage

Multifunctional polymer nanoconjugates containing multiple components show great promise in cancer therapy, but in most cases complete analysis of each component is difficult. Polymalic acid (PMLA) based nanoconjugates have demonstrated successful brain and breast cancer treatment. They consist of multiple components including targeting antibodies, Morpholino antisense oligonucleotides (AONs), and endosome escape moieties. The component analysis of PMLA nanoconjugates is extremely difficult using conventional spectrometry and HPLC method. Taking advantage of the nature of polyester of PMLA, which can be cleaved by ammonium hydroxide, we describe a method to analyze the content of antibody and AON within nanoconjugates simultaneously using SEC-HPLC by selectively cleaving the PMLA backbone. The selected cleavage conditions only degrade PMLA without affecting the integrity and biological activity of the antibody. Although the amount of antibody could also be determined using the bicinchoninic acid (BCA) method, our selective cleavage method gives more reliable results and is more powerful. Our approach provides a new direction for the component analysis of polymer nanoconjugates and nanoparticles.     

Separation of Xenon and Krypton in the Metal–Organic Frameworks M2(m-dobdc) (M=Co,Ni)

The separation of Xe and Kr from air is challenging owing both to the very low atmospheric concentrations of these gases and the need for their distillation at cryogenic temperatures. Alternatively, separation processes based on adsorption could provide a less energy-intensive route to the isolation of these gases. Here, we demonstrate that the metal–organic frameworks M₂(m-dobdc) (M=Co, Ni; m-dobdc⁴⁻=4,6-dioxido-1,3-benzenedicarboxylate) effectively separate Xe and Kr at ambient temperatures based on the different adsorption enthalpies of each gas at the coordinatively-unsaturated M²⁺ sites in each material. In situ Xe- and Kr-dosed powder X-ray diffraction studies further reveal key differences in the binding of Xe and Kr within the materials. In particular, while both gases adsorb near the framework open metal sites at 200 K, much higher Xe occupancies are observed at these sites relative to Kr, corroborating a stronger interaction of the polarizing M²⁺ cations with Xe. Further, while krypton is only found located above the open metal sites, two additional adsorption sites are observed for xenon, correlating with the stronger adsorption of Xe over Kr in these materials. These results suggest the possible utility of employing M₂(m-dobdc) materials in the adsorptive separation of Xe and Kr.     

Hybrid Photopatterned Enzymatic Reaction (HyPER) for in Situ Cell Manipulation

The ability to design artificial extracellular matrices as cell‐instructive scaffolds has opened the door to technologies capable of studying the fate of cells in vitro and to guiding tissue repair in vivo. One main component of the design of artificial extracellular matrices is the incorporation of biochemical cues to guide cell phenotype and multicellular organization. The extracellular matrix (ECM) is composed of a heterogeneous mixture of proteins that present a variety of spatially discrete signals to residing cell populations. In contrast, most engineered ECMs do not mimic this heterogeneity. In recent years, photo‐deprotection has been used to spatially immobilize signals. However, this approach has been limited mostly to small peptides. Here we combine photo‐deprotection with enzymatic reaction to achieve spatially controlled immobilization of active bioactive signals that range from small molecules to large proteins. A peptide substrate for transglutaminase factor XIII (FXIIIa) was caged with a photo‐deprotectable group, which was then immobilized to the bulk of a cell‐compatible hydrogel. With focused light, the substrate can be deprotected and used to immobilize patterned bioactive signals. This approach offers an innovative strategy to immobilize delicate bioactive signals, such as growth factors, without loss of activity and enables in situ cell manipulation of encapsulated cells.     

Discovery of Quinoline‐Derived Trifluoromethyl Alcohols,Determination of Their in vivo Toxicity and Anticancer Activity in a Zebrafish Embryo Model

In this study the rational design, synthesis, and anticancer activity of quinoline‐derived trifluoromethyl alcohols were evaluated. Members of this novel class of trifluoromethyl alcohols were identified as potent growth inhibitors in a zebrafish embryo model. Synthesis of these compounds was carried out with an sp³‐C?H functionalization strategy of methyl quinolines with trifluoromethyl ketones. A zebrafish embryo model was also used to explore the toxicity of ethyl 4,4,4‐trifluoro‐3‐hydroxy‐3‐(quinolin‐2‐ylmethyl)butanoate ( 1 ), 2‐benzyl‐1,1,1‐trifluoro‐3‐(quinolin‐2‐yl)propan‐2‐ol ( 2 ), and trifluoro‐3‐(isoquinolin‐1‐yl)‐2‐(thiophen‐2‐yl)propan‐2‐ol ( 3 ). Compounds 2 and 3 were found to be more toxic than compound 1 ; apoptotic staining assays indicated that compound 3 causes increased cell death. In vitro cell proliferation assays showed that compound 2 , with an LC₅₀ value of 14.14 μm , has more potent anticancer activity than cisplatin. This novel class of inhibitors provides a new direction in the discovery of effective anticancer agents.     

Seaweed Allelopathy Against Coral: Surface Distribution of a Seaweed Secondary Metabolite by Imaging Mass Spectrometry

Coral reefs are in global decline, with seaweeds increasing as corals decrease. Although seaweeds inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly understood. Here, we used field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting seaweed effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, neurymenolide A, as the main allelopathic agent. For allelopathy of lipid-soluble metabolites to be effective, the compounds would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify neurymenolide A on the surface of P. neurymenioides, and we found the molecule on all surfaces analyzed, with highest concentrations on basal portions of blades.