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Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

ABSTRACT: We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 ?m diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral attenuation.

SUBMITTER: Rymaruk MJ

PROVIDER: S-EPMC5047046 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

Rymaruk Matthew J MJ Thompson Kate L KL Derry Matthew J MJ Warren Nicholas J NJ Ratcliffe Liam P D LP Williams Clive N CN Brown Steven L SL Armes Steven P SP

Nanoscale 20160713 30

We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane dro ...[more]

PMID: 27406976

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Project description:Periodontitis (PD) as a chronic inflammatory disease instigated by periodontal pathogenic bacteria and mediated by the host immune response, resulting in the destruction of supporting periodontal tissue and tooth loss in adults. Constructing an injectable delivery system that allows for sustained drug release within periodontal pockets to continuously eliminate pathogenic bacteria, reduce periodontal inflammation, and promote periodontal tissue regeneration is an effective strategy for periodontitis treatment. Here, we explore the therapeutic potential and underlying mechanisms of curcumin-loaded Pickering emulsion (PE-CUR) in periodontitis treatment. The Pickering emulsion formulation offers an effective delivery system, enhancing curcumin's bioavailability and therapeutic efficacy. In vitro studies, we demonstrate that the PE-CUR exhibit excellent biocompatibility and anti-inflammatory property by elimination of reactive oxygen species (ROS). In addition, PE-CUR significantly eliminate key periodontal pathogens, including Porphyromonas gingivalis (P. gingivalis) and Staphylococcus aureus (S. aureus). In a rat model of periodontitis, PE-CUR significantly attenuates periodontal tissue inflammation and alveolar bone loss, indicating a protective effect against periodontal tissue destruction. Mechanistically, PE-CUR promotes the expression of anti-inflammatory factors and inhibits the release of pro-inflammatory factors by regulating macrophage polarization from M1 to M2 and modulating the MAPK and PI3K-AKT signaling pathway. Furthermore, PE-CUR decreases the formation of osteoclasts as well as stimulates the activation and differentiation of osteoblasts successively, thereby ameliorating the periodontal inflammation and promoting the alveolar bone regeneration. Overall, our findings elucidate the therapeutic mechanisms of PE-CUR in periodontitis, suggesting its potential as a promising treatment strategy warranting further clinical investigation.

Project description:RAFT dispersion polymerization of 2,2,2-trifluoroethyl methacrylate (TFEMA) is performed in n-dodecane at 90 °C using a relatively short poly(stearyl methacrylate) (PSMA) precursor and 2-cyano-2-propyl dithiobenzoate (CPDB). The growing insoluble poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) block results in the formation of PSMA-PTFEMA diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). GPC analysis indicated narrow molecular weight distributions (M w/M n ≤ 1.34) for all copolymers, with 19F NMR studies indicating high TFEMA conversions (≥95%) for all syntheses. A pseudo-phase diagram was constructed to enable reproducible targeting of pure spheres, worms, or vesicles by varying the target degree of polymerization of the PTFEMA block at 15-25% w/w solids. Nano-objects were characterized using dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering. Importantly, the near-identical refractive indices for PTFEMA (1.418) and n-dodecane (1.421) enable the first example of highly transparent vesicles to be prepared. The turbidity of such dispersions was examined between 20 and 90 °C. The highest transmittance (97% at 600 nm) was observed for PSMA9-PTFEMA294 vesicles (237 ± 24 nm diameter; prepared at 25% w/w solids) in n-dodecane at 20 °C. Interestingly, targeting the same diblock composition in n-hexadecane produced a vesicle dispersion with minimal turbidity at a synthesis temperature of 90 °C. This solvent enabled in situ visible absorption spectra to be recorded during the synthesis of PSMA16-PTFEMA86 spheres at 15% w/w solids, which allowed the relatively weak n→π* band at 515 nm assigned to the dithiobenzoate chain-ends to be monitored. Unfortunately, the premature loss of this RAFT chain-end occurred during the RAFT dispersion polymerization of TFEMA at 90 °C, so meaningful kinetic data could not be obtained. Furthermore, the dithiobenzoate chain-ends exhibited a λmax shift of 8 nm relative to that of the dithiobenzoate-capped PSMA9 precursor. This solvatochromatic effect suggests that the problem of thermally labile dithiobenzoate chain-ends cannot be addressed by performing the TFEMA polymerization at lower temperatures.

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Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

Publications

Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

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