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Physicochemical characterization and purification of cationic lipoplexes
1University of California, School of Pharmacy, Department of Biopharmaceutical Sciences and Pharmaceutical Chemistry, San Francisco, California 94143-0446 USA.
Biophysical Journal
|July 2, 1999
Summary
Cationic lipid-nucleic acid complexes (lipoplexes) were separated into charged components. Positively charged lipoplexes maintained transfection activity with reduced toxicity, while negatively charged ones showed enhanced activity and distinct structures.
Area of Science:
- Biophysical chemistry
- Materials science
- Gene delivery
Background:
- Cationic lipid-nucleic acid complexes (lipoplexes) are crucial for gene delivery.
- Understanding lipoplex structure and properties is key to optimizing their function.
Purpose of the Study:
- To investigate the structural and colloidal properties of lipoplexes prepared with DOTAP liposomes and plasmid DNA.
- To analyze the impact of charge ratio and component separation on lipoplex characteristics and transfection efficacy.
Main Methods:
- Preparation of lipoplexes at varying charge ratios using DOTAP and DNA.
- Separation of excess components via sucrose gradient ultracentrifugation.
- Characterization using electron microscopy (freeze-fracture and cryo-EM) and assessment of colloidal properties.
Main Results:
- Colloidal properties were dictated by the lipid/DNA charge ratio, independent of lipid composition.
- Separated positively charged lipoplexes retained high transfection activity and showed reduced toxicity.
- Separated negatively charged lipoplexes exhibited increased transfection activity and unique periodic internal structures.
Conclusions:
- Lipoplex colloidal properties are primarily determined by charge ratio.
- Separating charged components yields distinct lipoplexes with differential biological activity and structural organization.
- These findings offer insights into lipid-DNA packing and inform the design of improved gene delivery vectors.