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Perfluorocarbon-loaded Shell Crosslinked Knedel-like Nanoparticles: Lessons regarding polymer mobility and self
Andreas M Nyström1, Jeremy W Bartels, Wenjun Du
1Department of Chemistry and Department of Radiology, Washington University in Saint Louis, Saint Louis, Missouri 63130-4899 (USA).
Journal of Polymer Science. Part A, Polymer Chemistry
|February 17, 2010
Summary
Fluorinated nanoparticles synthesized using reversible addition-fragmentation chain transfer polymerization show potential for MRI contrast agents. However, chain mobility limitations in aqueous solutions require further investigation for effective (19)F-NMR spectroscopy applications.
Area of Science:
- Polymer Chemistry
- Materials Science
- Nanotechnology
Background:
- Controlled polymerization techniques are crucial for designing advanced materials.
- Fluorinated polymers offer unique properties for specialized applications, including biomedical imaging.
- Nanoparticle assembly enables the creation of functional materials with tailored characteristics.
Purpose of the Study:
- To synthesize gradient and block copolymers of styrene and pentafluorostyrene using RAFT polymerization.
- To create shell-crosslinked (SCK) nanoparticles from these copolymers for potential MRI contrast agent applications.
- To investigate the utility of (19)F-NMR spectroscopy for characterizing these fluorinated nanoparticles and their payload.
Main Methods:
- Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization for copolymer synthesis.
- Deprotection and grafting of poly(ethylene glycol) for amphiphilic block copolymer formation.
- Solution-state self-assembly and intramicellar crosslinking to form SCK nanoparticles.
- (19)F-NMR spectroscopy to assess chain mobility and payload encapsulation.
Main Results:
- Synthesis of well-defined gradient and block copolymers with controlled molecular weights and low polydispersity.
- Formation of uniform, small (approx. 20 nm) fluorinated SCK nanoparticles.
- Demonstrated that restricted chain mobility in the nanoparticle core hindered (19)F-NMR spectroscopy in aqueous dispersions.
- Successful encapsulation of perflouro-15-crown-5-ether (PFCE) into micelles, requiring a swelling solvent for (19)F-NMR signal observation.
Conclusions:
- RAFT polymerization provides excellent control over the synthesis of styrene-pentafluorostyrene copolymers and subsequent SCK nanoparticles.
- The fluorinated SCK nanoparticles are promising candidates for MRI contrast agents, but their application is limited by chain mobility issues affecting NMR detection.
- Strategies to enhance chain mobility, such as swelling with organic solvents, are necessary for effective characterization and potential in vivo applications of these fluorinated systems.
