Formation of divalent ion mediated anionic disc bicelle-DNA complexes

Area of Science:

• Biophysics
• Materials Science
• Gene Therapy

Background:

• Disc-shaped bicelles, formed from long and short-chain lipids, offer uniform size for novel applications.
• Traditional liposome-DNA complexes for gene therapy often use cationic or anionic lipids, with potential for cytotoxicity.
• Smaller bicelle structures present an opportunity for improved DNA packing and delivery.

Purpose of the Study:

• To investigate the formation and characteristics of anionic lipid bicelle-ion–DNA (AB–DNA) complexes.
• To explore the role of divalent ions, specifically calcium ions, in complex formation and DNA packing.
• To evaluate the potential of AB–DNA complexes as a safer alternative for gene therapy vectors.

Main Methods:

• Formation of AB–DNA complexes using anionic bicelles, DNA, and varying concentrations of calcium ions.
• Transmission Electron Microscopy (TEM) to visualize the morphology and size of the multi-stacked complexes.
• Small-Angle X-ray Scattering (SAXS) to study the interaction between DNA and anionic bicelles and ion-membrane phase transitions.

Main Results:

• Stable AB–DNA complexes were formed in the presence of 10 mM to 100 mM calcium ion concentrations.
• TEM revealed multi-stacked AB–DNA complexes with diameters of 50–100 nm and lengths of 50–150 nm.
• SAXS indicated that increasing calcium ion concentration above a critical point induced an ion-membrane phase, allowing for closer DNA packing and increased DNA loading capacity.

Conclusions:

• Anionic lipid bicelles can form stable complexes with DNA using divalent ions like calcium.
• The formation of an ion-membrane phase at higher calcium concentrations facilitates enhanced DNA packing within AB–DNA complexes.
• These findings suggest AB–DNA complexes are a promising, low-cytotoxicity alternative for gene delivery applications.