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Charge patch attraction and reentrant condensation in DNA-liposome complexes
S Sennato1, F Bordi, C Cametti
1Dipartimento di Fisica, Universita' di Roma La Sapienza, Piazzale A. Moro 5, I-00185-Rome, Italy.
Biochimica Et Biophysica Acta
|July 12, 2005
Summary
Cationic liposomes form complexes with anionic polyions like DNA and polyacrylates. Complex size depends on charge ratio, showing aggregation and reentrant condensation, explained by polyelectrolyte adsorption theories.
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Nanotechnology
Background:
- Cationic liposomes are crucial for gene delivery.
- Understanding polyion-liposome interactions is key to optimizing lipoplex formation.
- Polyion flexibility and charge density influence aggregate structure.
Purpose of the Study:
- To investigate complex formation between DOTAP-based cationic liposomes and anionic polyions (ssDNA, dsDNA, NaPAA).
- To compare the behavior of DNA with the more flexible polyacrylate (NaPAA) of similar charge density.
- To elucidate the mechanism of polyion-liposome aggregate (lipoplex) formation and size control.
Main Methods:
- Dynamic Light Scattering (DLS) for hydrodynamic properties.
- Transmission Electron Microscopy (TEM) for structural analysis.
- Systematic variation of polyion-liposome charge ratios.
Main Results:
- Complex formation is charge ratio-dependent, leading to large aggregate clusters.
- Aggregate size increases with polyion-liposome ratio, then decreases (reentrant condensation).
- Polyion charge density and flexibility significantly impact aggregate formation and stability.
Conclusions:
- Polyion-liposome interactions lead to charge inversion and reentrant condensation.
- The observed phenomena align with theories of correlated polyelectrolyte adsorption.
- This study provides insights into designing stable lipoplexes for various applications.