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Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release.

Mable CJ, Gibson RR, Prevost S, McKenzie BE, Mykhaylyk OO, Armes SP - J. Am. Chem. Soc. (2015)

Bottom Line: Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis.They may also serve as an active payload for self-healing hydrogels or repair of biological tissue.Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Sheffield , Brook Hill, Sheffield, South Yorkshire S3 7HF, United Kingdom.

ABSTRACT
Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be calculated using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ≈ 0.25 nm(-1). A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermoresponsive nature of the diblock copolymer vesicles enables thermally triggered release of the encapsulated silica nanoparticles simply by cooling to 0-10 °C, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes, or antibodies for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy.

No MeSH data available.


Related in: MedlinePlus

TEM images obtained for G58H250 diblock copolymervesicles synthesized in the presence of 5% w/w silica nanoparticles(see Figure 2) aftercooling to (a) 0 °C for 30 min, (b) 2 °C for 3 h, (c) 5°C for 57 h, and (d) 10 °C for 71 h. Cooling results inthe release of the encapsulated silica nanoparticles, which are moreelectron-dense than the copolymer nanoparticles (red circles depictfree silica nanoparticles). Cooling to 0 or 2 °C causes vesiclesto dissociate to spherical micelles and short worm-like micelles,cooling to 5 °C results in jellyfish, worms, and lamellae, andcooling to only 10 °C results in minimal vesicle disintegration.
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fig8: TEM images obtained for G58H250 diblock copolymervesicles synthesized in the presence of 5% w/w silica nanoparticles(see Figure 2) aftercooling to (a) 0 °C for 30 min, (b) 2 °C for 3 h, (c) 5°C for 57 h, and (d) 10 °C for 71 h. Cooling results inthe release of the encapsulated silica nanoparticles, which are moreelectron-dense than the copolymer nanoparticles (red circles depictfree silica nanoparticles). Cooling to 0 or 2 °C causes vesiclesto dissociate to spherical micelles and short worm-like micelles,cooling to 5 °C results in jellyfish, worms, and lamellae, andcooling to only 10 °C results in minimal vesicle disintegration.

Mentions: For silica-loaded G58H250 diblock copolymervesicles prepared in the presence of 5% w/w silica nanoparticles,a similar change in morphology was observed on cooling (see Figure 8a). Such vesicledissociation leads to release of the encapsulated silica nanoparticles,which results in loss of the silica structure factor in the correspondingSAXS pattern. Thus, this thermally triggered transition confirms thatthe silica nanoparticles are indeed encapsulated within the vesiclelumen.


Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release.

Mable CJ, Gibson RR, Prevost S, McKenzie BE, Mykhaylyk OO, Armes SP - J. Am. Chem. Soc. (2015)

TEM images obtained for G58H250 diblock copolymervesicles synthesized in the presence of 5% w/w silica nanoparticles(see Figure 2) aftercooling to (a) 0 °C for 30 min, (b) 2 °C for 3 h, (c) 5°C for 57 h, and (d) 10 °C for 71 h. Cooling results inthe release of the encapsulated silica nanoparticles, which are moreelectron-dense than the copolymer nanoparticles (red circles depictfree silica nanoparticles). Cooling to 0 or 2 °C causes vesiclesto dissociate to spherical micelles and short worm-like micelles,cooling to 5 °C results in jellyfish, worms, and lamellae, andcooling to only 10 °C results in minimal vesicle disintegration.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697924&req=5

fig8: TEM images obtained for G58H250 diblock copolymervesicles synthesized in the presence of 5% w/w silica nanoparticles(see Figure 2) aftercooling to (a) 0 °C for 30 min, (b) 2 °C for 3 h, (c) 5°C for 57 h, and (d) 10 °C for 71 h. Cooling results inthe release of the encapsulated silica nanoparticles, which are moreelectron-dense than the copolymer nanoparticles (red circles depictfree silica nanoparticles). Cooling to 0 or 2 °C causes vesiclesto dissociate to spherical micelles and short worm-like micelles,cooling to 5 °C results in jellyfish, worms, and lamellae, andcooling to only 10 °C results in minimal vesicle disintegration.
Mentions: For silica-loaded G58H250 diblock copolymervesicles prepared in the presence of 5% w/w silica nanoparticles,a similar change in morphology was observed on cooling (see Figure 8a). Such vesicledissociation leads to release of the encapsulated silica nanoparticles,which results in loss of the silica structure factor in the correspondingSAXS pattern. Thus, this thermally triggered transition confirms thatthe silica nanoparticles are indeed encapsulated within the vesiclelumen.

Bottom Line: Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis.They may also serve as an active payload for self-healing hydrogels or repair of biological tissue.Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Sheffield , Brook Hill, Sheffield, South Yorkshire S3 7HF, United Kingdom.

ABSTRACT
Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be calculated using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ≈ 0.25 nm(-1). A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermoresponsive nature of the diblock copolymer vesicles enables thermally triggered release of the encapsulated silica nanoparticles simply by cooling to 0-10 °C, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes, or antibodies for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy.

No MeSH data available.


Related in: MedlinePlus