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Colloidosomes represent a rapidly expanding field with various applications in microencapsulation, including the triggered release of cargoes. With self-assembled shells comprising ...colloidal particles, they offer significant flexibility with respect to microcapsule functionality. This review explores the various types of particles and techniques that have been employed to prepare colloidosomes. The relative advantages and disadvantages of these routes are highlighted and their potential as microcapsules for both small molecule and macromolecular actives is evaluated.
A poly(glycerol monomethacrylate) (PGMA) macromolecular chain transfer agent has been utilized to polymerize benzyl methacrylate (BzMA) via reversible addition–fragmentation chain transfer ...(RAFT)-mediated aqueous emulsion polymerization. This formulation leads to the efficient formation of spherical diblock copolymer nanoparticles at up to 50% solids. The degree of polymerization (DP) of the core-forming PBzMA block has been systematically varied to control the mean particle diameter from 20 to 193 nm. Conversions of more than 99% were achieved for PGMA51–PBzMA250 within 6 h at 70 °C using macro-CTA/initiator molar ratios ranging from 3.0 to 10.0. DMF GPC analyses confirmed that relatively low polydispersities (M w/M n < 1.30) and high blocking efficiencies could be achieved. These spherical nanoparticles are stable to both freeze–thaw cycles and the presence of added salt (up to 0.25 M MgSO4). Three sets of PGMA51–PBzMA x spherical nanoparticles have been used to prepare stable Pickering emulsions at various copolymer concentrations in four model oils: sunflower oil, n-dodecane, n-hexane, and isopropyl myristate. A reduction in mean droplet diameter was observed via laser diffraction on increasing the nanoparticle concentration. Finally, the cis diol functionality on the PGMA stabilizer chains has been exploited to demonstrate the selective adsorption of PGMA51–PBzMA100 nanoparticles onto a micropatterned phenylboronic acid-functionalized planar surface. Formation of a cyclic boronate ester at pH 10 causes strong selective binding of the nanoparticles via the cis-diol groups in the PGMA stabilizer chains, as judged by AFM studies. Control experiments confirmed that minimal selective nanoparticle binding occurred at pH 4, or if the PGMA51 stabilizer block was replaced with a poly(ethylene glycol) PEG113 stabilizer block.
Can Polymersomes Form Colloidosomes? Thompson, Kate L; Chambon, Pierre; Verber, Robert ...
Journal of the American Chemical Society,
08/2012, Letnik:
134, Številka:
30
Journal Article
Recenzirano
Hydroxy-functionalized polymersomes (or block copolymer vesicles) were prepared via a facile one-pot RAFT aqueous dispersion polymerization protocol and evaluated as Pickering emulsifiers for the ...stabilization of emulsions of n-dodecane emulsion droplets in water. Linear polymersomes produced polydisperse oil droplets with diameters of ∼50 μm regardless of the polymersome concentration in the aqueous phase. Introducing an oil-soluble polymeric diisocyanate cross-linker into the oil phase prior to homogenization led to block copolymer microcapsules, as expected. However, TEM inspection of these microcapsules after an alcohol challenge revealed no evidence for polymersomes, suggesting these delicate nanostructures do not survive the high-shear emulsification process. Thus the emulsion droplets are stabilized by individual diblock copolymer chains, rather than polymersomes. Cross-linked polymersomes (prepared by the addition of ethylene glycol dimethacrylate as a third comonomer) also formed stable n-dodecane-in-water Pickering emulsions, as judged by optical and fluorescence microscopy. However, in this case the droplet diameter varied from 50 to 250 μm depending on the aqueous polymersome concentration. Moreover, diisocyanate cross-linking at the oil/water interface led to the formation of well-defined colloidosomes, as judged by TEM studies. Thus polymersomes can indeed stabilize colloidosomes, provided that they are sufficiently cross-linked to survive emulsification.
Translocator protein 18 kDa (TSPO) is an outer-mitochondrial membrane transporter which has many functions including participation in the mitochondrial permeability transition pore, regulation of ...reactive oxygen species (ROS), production of cellular energy, and is the rate-limiting step in the uptake of cholesterol. TSPO expression is dysregulated during disease pathologies involving changes in tissue energy demands such as cancer, and is up-regulated in activated macrophages during the inflammatory response. Obesity is associated with decreased energy expenditure, mitochondrial dysfunction, and chronic low-grade inflammation which collectively contribute to the development of the Metabolic Syndrome. Therefore, we hypothesized that dysregulation of TSPO in adipose tissue may be a feature of disease pathology in obesity. Radioligand binding studies revealed a significant reduction in TSPO ligand binding sites in mitochondrial extracts from both white (WAT) and brown adipose tissue (BAT) in mouse models of obesity (diet-induced and genetic) compared to control animals. We also confirmed a reduction in TSPO gene expression in whole tissue extracts from WAT and BAT. Immunohistochemistry in WAT confirmed TSPO expression in adipocytes but also revealed high-levels of TSPO expression in WAT macrophages in obese animals. No changes in TSPO expression were observed in WAT or BAT after a 17 hour fast or 4 hour cold exposure. Treatment of mice with the TSPO ligand PK11195 resulted in regulation of metabolic genes in WAT. Together, these results suggest a potential role for TSPO in mediating adipose tissue homeostasis.
High-pressure microfluidization is used to prepare a series of oil-in-water Pickering nanoemulsions using sterically-stabilized diblock copolymer nanoparticles as the Pickering emulsifier. The ...droplet phase comprised either n-octane, n-decane, n-dodecane, or n-tetradecane. This series of oils enabled the effect of aqueous solubility on Ostwald ripening to be studied, which is the primary instability mechanism for such nanoemulsions. Analytical centrifugation (LUMiSizer instrument) was used to evaluate the long-term stability of these Pickering nanoemulsions over time scales of weeks/months. This technique enables convenient quantification of the fraction of growing oil droplets and confirmed that using n-octane (aqueous solubility = 0.66 mg dm–3 at 20 °C) leads to instability even over relatively short time periods. However, using n-tetradecane (aqueous solubility = 0.386 μg dm–3 at 20 °C) leads to significantly improved long-term stability with respect to Ostwald ripening, with all droplets remaining below 1 μm diameter after 6 weeks storage at 20 °C. In the case of n-dodecane, the long-term stability of these new copolymer-stabilized Pickering nanoemulsions is significantly better than the silica-stabilized Pickering nanoemulsions reported in the literature by Persson et al. (Colloids Surf., A, 2014, 459, 48–57). This is attributed to a much greater interfacial yield stress for the former system, as recently described in the literature (see P. J. Betramo et al. Proc. Natl. Acad. Sci. U.S.A., 2017, 114, 10373–10378).
•Staphylococcal products elevate protease activity in a 3D wound model.•Staphylococcal-mediated proteases delay the proliferative phase of wound healing.•ORC/collagen dressing reverses protease ...levels in inflamed wound model to offset.•Dressing application accelerates the rate of wound healing.
Elevated protease activity is a characteristic feature of chronic wounds, where the inflammatory phase of wound healing is prolonged. The choice of dressings in treatment of chronic wounds can change the nature of the wound base and have a significant impact on healing.
To evaluate the impact of oxidised regenerated cellulose/collagen dressings on Staphylococcal-mediated protease activity in an inflamed wound model.
We developed an in vitro 3D inflamed wound model, and simulated inflammation by exposing the models to Staphylococcal spent culture supernatant. Protease activity and wound healing were assessed in the presence/absence of the dressings.
Histological analysis of the wound model revealed two distinct layers, an epidermal and dermal layer, similar to the organisation of human skin. Inflammation with Staphylococcal spent culture supernatant elevated protease levels by 1.7x and consequently prevented the wound from progressing to the proliferative phase of healing, without having a negative effect on cell viability. Adding a collagen dressing, known to have non-specific protease modulating properties, reduced Staphylococcal-mediated protease activity back to baseline, with a concomitant reduction in wound closure time. Inflamed wounds thus resembled unwounded skin after 10 days of treatment with the dressings.
Our findings support the further evaluation and use of oxidised regenerated cellulose/collagen dressings for inflamed, non-healing wounds in the clinical setting. The model used in this study has the potential to be applied in preclinical research; to test wound dressing performance, such as healing and cell viability, and to also assess key markers of inflammation.
Offshore wind power provides a valuable source of renewable energy that can help reduce carbon emissions. Technological advances are allowing higher capacity turbines to be installed and in deeper ...water, but there is still much that is unknown about the effects on the environment. Here we describe the lessons learned based on the recent literature and our experience with assessing impacts of offshore wind developments on marine mammals and seabirds, and make recommendations for future monitoring and assessment as interest in offshore wind energy grows around the world. The four key lessons learned that we discuss are: 1) Identifying the area over which biological effects may occur to inform baseline data collection and determining the connectivity between key populations and proposed wind energy sites, 2) The need to put impacts into a population level context to determine whether they are biologically significant, 3) Measuring responses to wind farm construction and operation to determine disturbance effects and avoidance responses, and 4) Learn from other industries to inform risk assessments and the effectiveness of mitigation measures. As the number and size of offshore wind developments increases, there will be a growing need to consider the population level consequences and cumulative impacts of these activities on marine species. Strategically targeted data collection and modeling aimed at answering questions for the consenting process will also allow regulators to make decisions based on the best available information, and achieve a balance between climate change targets and environmental legislation.
Abstract Objectives The aim of this study was to determine the acceleration (≥2 m s−2 ) and deceleration (≤ − 2 m s−2 ) profiles of elite female soccer players during competitive matches. Design ...Single cohort, observational study. Methods An Optical Player Tracking system was used to determine acceleration (≥2 m s−2 ) and deceleration (≤ − 2 m s−2 ) variables for twelve elite female players across seven competitive matches. Results In total, players performed 423 (±126) accelerations and 430 (±125) decelerations per match. It was shown that the number of accelerations (p = 0.003–0.034, partial η2 = 0.229–321) and decelerations (p = 0.012–0.031, partial η2 = 0.233–275) at different intensities (based on the start and final velocity) varied according to player position. Mean and maximum distance per effort was 1–4 m and 2–8 m, respectively, and differed between each intensity category (p < 0.001, partial η2 = 0.753–0.908). The mean time between efforts was 14 s for both accelerations (±5 s) and decelerations (±4 s) and fluctuated between 15 min time periods (p < 0.001, partial η2 = 0.148–0.206). Conclusions The acceleration and deceleration profiles varied according to player position and time period of the match. The results of this study can be used to design match-specific acceleration and deceleration drills to enhance change of speed ability.
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