Complexation of lipofectamine and cholesterol-modified DNA sequences studied by single-molecule fluorescence...

Area of Science:

• Biophysical Chemistry
• Nanotechnology
• Molecular Biology

Background:

• Lipoplexes are crucial for oligonucleotide delivery, but their formation and characteristics are complex.
• Understanding lipoplex heterogeneity is key to optimizing gene delivery systems.
• Cholesterol modification of oligonucleotides has shown promise in enhancing transfection efficiency.

Purpose of the Study:

• To investigate lipoplex formation for normal and cholesterol-modified oligonucleotides using fluorescence correlation spectroscopy (FCS).
• To develop a novel analytical approach for characterizing heterogeneous lipoplex systems.
• To correlate lipoplex characteristics with oligonucleotide transfection efficiency.

Main Methods:

• Utilized fluorescence correlation spectroscopy (FCS) for detailed analysis of lipoplex formation.
• Developed a new method to separately analyze baseline fluorescence and fluorescence bursts in FCS traces.
• Applied various mathematical models to estimate lipoplex size, DNA content, and lipid composition.

Main Results:

• The novel FCS analysis method enabled detailed characterization of heterogeneous lipoplex systems.
• Estimated the presence of tens to hundreds of nanometer-sized lipoplexes and quantified DNA/lipid components.
• Identified the formation of large-sized lipoplexes from cholesterol-modified oligonucleotides.

Conclusions:

• Cholesterol modification leads to the formation of larger lipoplexes.
• The size of lipoplexes directly correlates with enhanced oligonucleotide transfection efficiency.
• The developed FCS analytical approach provides deeper insights into lipoplex systems for improved gene delivery applications.