Gas Bubbles Stabilized by Janus Particles with Varying Hydrophilic–Hydrophobic Surface Characteristics

Micrometer-sized polymer-grafted gold–silica (Au-SiO₂) Janus particles were fabricated by vacuum evaporation followed by polymer grafting. The Janus particle diameter, diameter distribution, morphology, surface chemistry, and water wettability were characterized by optical microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The optical microscopy results showed that the polystyrene (PS)-grafted Au-SiO₂ Janus particles exhibited monolayer adsorption at the air–water interface and could stabilize bubbles, preventing their coalescence for more than 1 month. The hydrophobic PS-grafted Au and hydrophilic SiO₂ surfaces were exposed to the air and water phases, respectively. Bare Au-SiO₂ and poly­(2-(per­fluoro­butyl)­ethyl meth­acrylate) (PPFBEM)-grafted Au-SiO₂ Janus particles could also stabilize bubbles for up to 2 weeks. By contrast, bare silica particles did not stabilize bubbles and were dispersed in water. The bubbles that formed in the PS-grafted Janus particle system were more stable than those formed in the bare Au-SiO₂ Janus particles, PPFBEM-grafted Au-SiO₂ Janus particles, and SiO₂ particle systems because of the high adsorption energy of the PS-grafted particles at the air–water interface

Micrometer-Sized Gold–Silica Janus Particles as Particulate Emulsifiers

Micrometer-sized gold–silica Janus particles act as an effective stabilizer of emulsions by adsorption at the oil–water interface. The Janus particles were adsorbed at the oil–water interface as a monolayer and stabilized near-spherical and nonspherical oil droplets that remained stable without coalescence for longer than one year. Gold and silica surfaces have hydrophobic and hydrophilic features; these surfaces were exposed to oil and water phases, respectively. In contrast, bare silica particles cannot stabilize stable emulsion, and completed demulsification occurred within 2 h. Greater stability of the emulsion for the Janus particle system compared to the silica particle system was achieved by using the adsorption energy of the Janus particles at the oil–water interface; the adsorption energy of the Janus particles is more than 3 orders of magnitude greater than that of silica particles. Suspension polymerization of Janus particle-stabilized vinyl monomer droplets in the absence of any molecular-level emulsifier in aqueous media led to nonspherical microspheres with Janus particles on their surface. Furthermore, polymer microspheres carrying Au femtoliter cups on their surfaces were successfully fabricated by removal of the silica component from the Janus-particle stabilized microspheres

Reduced CSF Water Influx in Alzheimer’s Disease Supporting the β-Amyloid Clearance Hypothesis

<div><p>Objective</p><p>To investigate whether water influx into cerebrospinal fluid (CSF) space is reduced in Alzheimer’s patients as previously shown in the transgenic mouse model for Alzheimer’s disease.</p><p>Methods</p><p>Ten normal young volunteers (young control, 21-30 years old), ten normal senior volunteers (senior control, 60-78 years old, MMSE ≥ 29), and ten Alzheimer’s disease (AD) patients (study group, 59-84 years old, MMSE: 13-19) participated in this study. All AD patients were diagnosed by neurologists specializing in dementia based on DSM-IV criteria. CSF dynamics were analyzed using positron emission tomography (PET) following an intravenous injection of 1,000 MBq [¹⁵O]H₂O synthesized on-line.</p><p>Results</p><p>Water influx into CSF space in AD patients, expressed as influx ratio, (0.755 ± 0.089) was significantly reduced compared to young controls (1.357 ± 0.185; p < 0.001) and also compared to normal senior controls (0.981 ± 0.253, p < 0.05). Influx ratio in normal senior controls was significantly reduced compared to young controls (p < 0.01).</p><p>Conclusion</p><p>Water influx into the CSF is significantly reduced in AD patients. β-amyloid clearance has been shown to be dependent on interstitial flow and CSF production. The current study indicates that reduction in water influx into the CSF may disturb the clearance rate of β-amyloid, and therefore be linked to the pathogenesis of AD.</p><p>Trial Registration</p><p>UMIN Clinical Trials Registry <a href="https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000013940&type=summary&language=E" target="_blank">UMIN000011939</a></p></div

Schematic presentation of the results with mean (circle) and standard deviation (bar).

<p>Water influx into CSF space is expressed as influx ratio (IR): the ratio between the standardized uptake value (SUV, g/ml) of the ventricle to that of cortex. IR in Alzheimer’s disease patients (AD) is significantly reduced compared to both young controls (p < 0.001) and senior controls (p < 0.05), Mann-Whitney-Wilcoxon rank sum test. Note that there is no overlap in data points between AD and young controls. Reduction of influx ratio in senior controls compared to that in young control is found to be significant (p < 0.01) as well. A large range of influx ratio in senior controls suggests that the observed reduction likely represents one of the aging processes.</p

Consort Flow Diagram providing details of participant enrolment.

<p>Consort Flow Diagram providing details of participant enrolment.</p