Synthesis of Neutral, Water-Soluble Oligo–Ethylene Glycol-Containing Dendronized Homo- and Copolymers of Generations 1, 1.5, 2, and 3

Oligo-ethylene glycol-containing dendronized monomers <b>MG1</b>, <b>MG1.5</b>, <b>MG2</b>, and <b>MG3</b> were synthesized in a particularly easy fashion on the gram scale involving only few steps. Their corresponding homopolymers (<b>PG1</b>, <b>PG1.5</b>, <b>PG2</b>, and <b>PG3</b>) and copolymers (<b>PG1</b><i><b>co</b></i><b>2, PG1</b><i><b>co</b></i><b>3</b>, and <b>PG2</b><i><b>co</b></i><b>3</b>) were synthesized via free radical polymerization. All the polymers are soluble in water and also in organic solvents such as DCM, CHCl₃, 1,4-dioxolane, DMF, and DMSO. Their glass transition temperatures (<i>T</i>_g) are in the range −68 °C < <i>T</i>_g < −48 °C and thus rather low. All polymers show thermoresponsive behavior which was investigated by turbidity measurements. Interestingly, a 1:1 mixture of homopolymers <b>PG1</b> and <b>PG2</b> behaves identical with <b>PG1</b> alone, while the collapse curve of copolymer <b>PG1</b><i><b>co</b></i><b>2</b> is almost superimposable with that of <b>PG2</b> alone. Thus, in the former case <b>PG1</b> dominates the thermoresponsive behavior while in the latter this is done by the G2-dendrons in the copolymer. Finally, the polymer chains were visualized by AFM, confirming the rod-like behavior of these rigidified polymers

Probing the Effect of Salt on Asphaltene Aggregation in Aqueous Solutions Using Molecular Dynamics Simulations

The presence of salts in different processes of oil production has attracted wide attention because of its effects on asphaltene aggregation, stability, interactions of emulsions, etc. In this work, molecular dynamics simulations were employed to study the effect of salts on aggregation of model asphaltenes. Four types of polyaromatic compounds possessing key structural features of continental-type asphaltenes were dispersed into NaCl solutions of different concentrations. These models have the same polyaromatic core but different lengths for the side chains. In the two models with relatively long side chains, the hydrophobic association among side chains is the main driving force for aggregation. The effect of salt on aggregation is therefore closely tied to its influence on the hydrophobic interaction: the salt ions promote the hydrophobic interaction at a low salt concentration while suppressing it at a high salt concentration. For the model with an intermediate side chain length, the hydrophobic interaction between side chains becomes less dominant and the salt has mutual influences on the core–core, chain–chain, and core–chain interactions. For the model with the shortest side chains, although the core–core and core–chain interactions are more important, the side chains still play a role in aggregation when the salt is present. Our results provide new insights into the fundamental understanding of the influence of salts on the aggregation and interaction behaviors of polyaromatic compounds in an aqueous environment

Cellular Contact Guidance through Dynamic Sensing of Nanotopography

We investigate the effects of surface nanotopography on the migration and cell shape dynamics of the amoeba <i>Dictyostelium discoideum</i>. Multiple prior studies have implicated the patterning of focal adhesions in contact guidance. However, we observe significant contact guidance of <i>Dictyostelium</i> along surfaces with nanoscale ridges or grooves, even though this organism lacks integrin-based adhesions. Cells that move parallel to nanoridges are faster, more protrusive at their fronts, and more elongated than are cells that move perpendicular to nanoridges. Quantitative studies show that nanoridges spaced 1.5 μm apart exhibit the greatest contact guidance efficiency. Because <i>Dictyostelium</i> cells exhibit oscillatory shape dynamics, we model contact guidance as a process in which stochastic cellular harmonic oscillators couple to the periodicity of the nanoridges. In support of this connection, we find that nanoridges nucleate actin polymerization waves of nanoscale width that propagate parallel to the nanoridges

Unraveling Partial Coalescence Between Droplet and Oil–Water Interface in Water-in-Oil Emulsions under a Direct-Current Electric Field via Molecular Dynamics Simulation

When the electric field strength (E) surpasses a certain threshold, secondary droplets are generated during the coalescence between water droplets in oil and the oil–water interface (so-called the droplet-interface partial coalescence phenomenon), resulting in a lower efficiency of droplet electrocoalescence. This study employs molecular dynamics (MD) simulations to investigate the droplet-interface partial coalescence phenomenon under direct current (DC) electric fields. The results demonstrate that intermolecular interactions, particularly the formation of hydrogen bonds, play a crucial role in dipole–dipole coalescence. Droplet-interface partial coalescence is categorized into five regimes based on droplet morphology. During the contact and fusion of the droplet with the water layer, the dipole moment of the droplet exhibits alternating increases and decreases along the electric field direction. Electric field forces acting on sodium ions and the internal interactions within droplets promote the process of droplet-interface partial coalescence. High field strengths cause significant elongation of the droplet, leading to its fragmentation into multiple segments. The migration of hydrated ions has a dual impact on the droplet-interface partial coalescence, with both facilitative and suppressive effects. The time required for droplet-interface partial coalescence initially decreases and subsequently increases as the field strength increases, depending on the competitive relationship between the extent of droplet stretching and the electric field force. This work provides molecular insights into the droplet-interface coalescence mechanisms in water-in-oil emulsions under DC electric fields

Unraveling Partial Coalescence Between Droplet and Oil–Water Interface in Water-in-Oil Emulsions under a Direct-Current Electric Field via Molecular Dynamics Simulation

When the electric field strength (E) surpasses a certain threshold, secondary droplets are generated during the coalescence between water droplets in oil and the oil–water interface (so-called the droplet-interface partial coalescence phenomenon), resulting in a lower efficiency of droplet electrocoalescence. This study employs molecular dynamics (MD) simulations to investigate the droplet-interface partial coalescence phenomenon under direct current (DC) electric fields. The results demonstrate that intermolecular interactions, particularly the formation of hydrogen bonds, play a crucial role in dipole–dipole coalescence. Droplet-interface partial coalescence is categorized into five regimes based on droplet morphology. During the contact and fusion of the droplet with the water layer, the dipole moment of the droplet exhibits alternating increases and decreases along the electric field direction. Electric field forces acting on sodium ions and the internal interactions within droplets promote the process of droplet-interface partial coalescence. High field strengths cause significant elongation of the droplet, leading to its fragmentation into multiple segments. The migration of hydrated ions has a dual impact on the droplet-interface partial coalescence, with both facilitative and suppressive effects. The time required for droplet-interface partial coalescence initially decreases and subsequently increases as the field strength increases, depending on the competitive relationship between the extent of droplet stretching and the electric field force. This work provides molecular insights into the droplet-interface coalescence mechanisms in water-in-oil emulsions under DC electric fields

Protease-Activated Ratiometric Fluorescent Probe for pH Mapping of Malignant Tumors

A protease-activated ratiometric fluorescent probe based on fluorescence resonance energy transfer between a pH-sensitive fluorescent dye and biocompatible Fe₃O₄ nanocrystals was constructed. A peptide substrate of MMP-9 served as a linker between the particle quencher and the chromophore that was covalently attached to the antitumor antibody. The optical response of the probe to activated MMP-9 and gastric cell line SGC7901 tumor cells was investigated, followed by <i>in vivo</i> tumor imaging. Based on the ratiometric pH response to the tumor microenvironment, the resulting probe was successfully used to image the pH of subcutaneous tumor xenografts

Cross-cohort comparisons of VMHC.

<p><b>A</b>: The AD subjects showed significantly decreased VMHC in the OFC, ACC, POC, NAcc, putamen, caudate and insula compared to CN. <b>B</b>: The AD subjects showed significantly decreased VMHC in the OFC, putamen, caudate, insula, SMC, and OcG compared to MCI. <b>C</b>: The MCI subjects showed significantly increased VMHC in the SMC compared to CN. <b>D-H</b> show the locations of the five anatomical structures where the VMHC was significantly different across the three cohorts. The values in the bar graphs are z-scores transformed from the VMHC values. * represents statistical differences between groups (*, <i>p</i> ≤ 0.05; ***, <i>p</i> ≤ 0.001).</p

Normative VMHC map of the CN group (one-sample t-test, family-wise error corrected, p < 0.001, extent threshold = 10).

<p>Normative VMHC map of the CN group (one-sample t-test, family-wise error corrected, p < 0.001, extent threshold = 10).</p

Correlation between diffusion parameters, volume of the genu of corpus callosum, VMHC, and MMSE scores of all the subjects.

<p>The values in the table are the correlation coefficients and corresponding p-values (partial correlation with age effect corrected).</p><p>*, p ≤ 0.05;</p><p>**, p ≤ 0.01;</p><p>***, p ≤ 0.001.</p><p>Abbreviations: FA, fractional anisotropy; MD, mean diffusivity (×10–3 mm2/s); λ‖, axial diffusivity (×10–3 mm2/s); λ┴, radial diffusion (×10–3 mm2/s); VMHC, voxel mirror homotopic connectivity; OFC, orbitofrontal cortex; ACC, anterior cingulate cortex; NAcc, nucleus accumbens; SMC, sensorimotor cortex; OcG, occipital gyrus.</p><p>Correlation between diffusion parameters, volume of the genu of corpus callosum, VMHC, and MMSE scores of all the subjects.</p

DTI and volumetric differences among AD, MCI and CN.

<p><b>A:</b> Voxel-based analysis showed significant difference of FA between AD and CN in the genu of the corpus callosum (family-wise error corrected, <i>p</i> < 0.05, extent threshold = 10). <b>B-F:</b> Group comparisons revealed the patterns of diffusion parameters and volume changes in the genu of the corpus callosum (FA: AD < MCI < CN; MD: AD > CN / MCI; λ_┴: AD > CN / MCI; λ_‖: no difference; Volume: AD < CN/MCI). * represents statistical differences between groups (*, <i>p</i> ≤ 0.05; ***, <i>p</i> ≤ 0.001)</p