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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

Cryo-TEM images obtainedfor (a) empty G58H250 diblock copolymer vesicles,(b) G58H250 diblockcopolymer vesicles prepared in the presence of 20% w/w silica nanoparticles(after centrifugation to remove excess silica nanoparticles), and(c) the silica nanoparticles alone, for which the SAXS-derived vesiclediameter (Dv) is 18.4 nm.
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fig3: Cryo-TEM images obtainedfor (a) empty G58H250 diblock copolymer vesicles,(b) G58H250 diblockcopolymer vesicles prepared in the presence of 20% w/w silica nanoparticles(after centrifugation to remove excess silica nanoparticles), and(c) the silica nanoparticles alone, for which the SAXS-derived vesiclediameter (Dv) is 18.4 nm.

Mentions: Hypothetically, these TEM observations could bethe result of dryingartifacts. In contrast, cryo-TEM allows the direct observation ofhydrated vesicles that have not been dried, stained, or fixed; thus,this technique is much more representative of their native environment.Cryo-TEM images (see Figure 3) confirm that the silica nanoparticles are indeed locatedinside the vesicle lumen. Both DLS and TEM studies indicate that thevesicle diameter is essentially unchanged, regardless of the initialsilica concentration, [silica]0.


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)

Cryo-TEM images obtainedfor (a) empty G58H250 diblock copolymer vesicles,(b) G58H250 diblockcopolymer vesicles prepared in the presence of 20% w/w silica nanoparticles(after centrifugation to remove excess silica nanoparticles), and(c) the silica nanoparticles alone, for which the SAXS-derived vesiclediameter (Dv) is 18.4 nm.
© Copyright Policy
Related In: Results  -  Collection

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

fig3: Cryo-TEM images obtainedfor (a) empty G58H250 diblock copolymer vesicles,(b) G58H250 diblockcopolymer vesicles prepared in the presence of 20% w/w silica nanoparticles(after centrifugation to remove excess silica nanoparticles), and(c) the silica nanoparticles alone, for which the SAXS-derived vesiclediameter (Dv) is 18.4 nm.
Mentions: Hypothetically, these TEM observations could bethe result of dryingartifacts. In contrast, cryo-TEM allows the direct observation ofhydrated vesicles that have not been dried, stained, or fixed; thus,this technique is much more representative of their native environment.Cryo-TEM images (see Figure 3) confirm that the silica nanoparticles are indeed locatedinside the vesicle lumen. Both DLS and TEM studies indicate that thevesicle diameter is essentially unchanged, regardless of the initialsilica concentration, [silica]0.

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