Single lipoplex study of cationic lipoid-DNA, self-assembled complexes

Area of Science:

• Biophysical Chemistry
• Nanotechnology
• Molecular Biology

Background:

• Cationic lipoid-DNA complexes (lipoplexes) are vital for gene delivery.
• Traditional methods analyze bulk properties, masking individual particle heterogeneity.
• Understanding lipoplex formation is key to optimizing gene transfection.

Purpose of the Study:

• To characterize individual cationic lipoid-DNA complexes using flow fluorometric analysis.
• To determine the composition and formation kinetics of lipoplexes under various conditions.
• To differentiate between lipoplex heterogeneity sources: within vesicles vs. between lipoplexes.

Main Methods:

• Utilized a commercial flow cytometer for single lipoplex analysis.
• Analyzed statistically large ensembles (10^3-10^4 particles).
• Varied conditions: DNA:lipoid ratio, lipoid dispersion, DNA morphology, and concentration.

Main Results:

• Identified two distinct lipoplex formation regimes: (1) coexistence of multilamellar lipoplexes and DNA-coated vesicles, and (2) highly fused multilamellar complexes.
• Regime 1 favored by excess DNA, small vesicle size, linear DNA, high concentration, and short incubation.
• Fused complexes, essential for transfection, formed via DNA-coated vesicle interaction and breakdown.

Conclusions:

• Single lipoplex analysis provides detailed characterization beyond population averages.
• Lipoplex composition and heterogeneity can be precisely determined.
• This approach offers insights into lipoplex formation mechanisms and their implications for gene delivery efficacy.