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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

SAXS patterns obtained for 1.0% w/w aqueous dispersions of G58H250 diblock copolymer vesicles (originally preparedvia PISA at 10% w/w copolymer in the presence of 5% w/w silica). Theexcess/non-encapsulated silica nanoparticles were removed via sixcentrifugation–redispersion cycles. Then the purified silica-loadedG58H250 vesicles were cooled to 0 °C for30 min while scattering patterns were collected every 15 s. SelectedSAXS patterns recorded after various times at 0 °C are shown(for clarity, these patterns are shifted vertically by an arbitraryscaling factor). Silica-loaded vesicles are present up to 8 min (redcircles) but undergo dissociation to form worm-like micelles after9 min (green circles), followed by further transformation to producemainly spheres after 12 min (blue circles).
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fig9: SAXS patterns obtained for 1.0% w/w aqueous dispersions of G58H250 diblock copolymer vesicles (originally preparedvia PISA at 10% w/w copolymer in the presence of 5% w/w silica). Theexcess/non-encapsulated silica nanoparticles were removed via sixcentrifugation–redispersion cycles. Then the purified silica-loadedG58H250 vesicles were cooled to 0 °C for30 min while scattering patterns were collected every 15 s. SelectedSAXS patterns recorded after various times at 0 °C are shown(for clarity, these patterns are shifted vertically by an arbitraryscaling factor). Silica-loaded vesicles are present up to 8 min (redcircles) but undergo dissociation to form worm-like micelles after9 min (green circles), followed by further transformation to producemainly spheres after 12 min (blue circles).

Mentions: SAXS was utilized to explore the kinetics of silica nanoparticlerelease at 0 °C (see Figure 9). Time-resolved SAXS studies indicated that intactsilica-loaded vesicles were still present after 6 min at 0 °C.Close inspection of these SAXS patterns confirmed that the local minimumat q ≈ 0.02 nm–1, whichis associated with the vesicle form factor, disappeared after 9 minat 0 °C. Moreover, the gradient of the scattering pattern atlow q is reduced from −2 to −1 after9 min, indicating the formation of worm-like micelles. This gradienttends to zero after 12 min at 0 °C, suggesting further vesicledissociation to form a mixture of spheres and short worm-like micelles.Furthermore, the final pattern after 30 min at 0 °C is identicalto that obtained after 12 min, confirming that the morphological transitionis essentially complete after 12 min. Further time-resolved SAXS studieswere conducted for silica-loaded vesicles prepared in the presenceof 10–35% w/w silica nanoparticles, which will be reportedelsewhere in due course.


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)

SAXS patterns obtained for 1.0% w/w aqueous dispersions of G58H250 diblock copolymer vesicles (originally preparedvia PISA at 10% w/w copolymer in the presence of 5% w/w silica). Theexcess/non-encapsulated silica nanoparticles were removed via sixcentrifugation–redispersion cycles. Then the purified silica-loadedG58H250 vesicles were cooled to 0 °C for30 min while scattering patterns were collected every 15 s. SelectedSAXS patterns recorded after various times at 0 °C are shown(for clarity, these patterns are shifted vertically by an arbitraryscaling factor). Silica-loaded vesicles are present up to 8 min (redcircles) but undergo dissociation to form worm-like micelles after9 min (green circles), followed by further transformation to producemainly spheres after 12 min (blue circles).
© Copyright Policy
Related In: Results  -  Collection

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

fig9: SAXS patterns obtained for 1.0% w/w aqueous dispersions of G58H250 diblock copolymer vesicles (originally preparedvia PISA at 10% w/w copolymer in the presence of 5% w/w silica). Theexcess/non-encapsulated silica nanoparticles were removed via sixcentrifugation–redispersion cycles. Then the purified silica-loadedG58H250 vesicles were cooled to 0 °C for30 min while scattering patterns were collected every 15 s. SelectedSAXS patterns recorded after various times at 0 °C are shown(for clarity, these patterns are shifted vertically by an arbitraryscaling factor). Silica-loaded vesicles are present up to 8 min (redcircles) but undergo dissociation to form worm-like micelles after9 min (green circles), followed by further transformation to producemainly spheres after 12 min (blue circles).
Mentions: SAXS was utilized to explore the kinetics of silica nanoparticlerelease at 0 °C (see Figure 9). Time-resolved SAXS studies indicated that intactsilica-loaded vesicles were still present after 6 min at 0 °C.Close inspection of these SAXS patterns confirmed that the local minimumat q ≈ 0.02 nm–1, whichis associated with the vesicle form factor, disappeared after 9 minat 0 °C. Moreover, the gradient of the scattering pattern atlow q is reduced from −2 to −1 after9 min, indicating the formation of worm-like micelles. This gradienttends to zero after 12 min at 0 °C, suggesting further vesicledissociation to form a mixture of spheres and short worm-like micelles.Furthermore, the final pattern after 30 min at 0 °C is identicalto that obtained after 12 min, confirming that the morphological transitionis essentially complete after 12 min. Further time-resolved SAXS studieswere conducted for silica-loaded vesicles prepared in the presenceof 10–35% w/w silica nanoparticles, which will be reportedelsewhere in due course.

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