Abstract
The use of non-viral vectors for in vivo gene therapy could drastically increase safety, whilst reducing the cost of preparing the vectors. A promising approach to non-viral vectors makes use of DNA/cationic liposome complexes (lipoplexes) to deliver the genetic material. Here we use coarse-grained molecular dynamics simulations to investigate the molecular mechanism underlying efficient DNA transfer from lipoplexes. Our computational fusion experiments of lipoplexes with endosomal membrane models show two distinct modes of transfection: parallel and perpendicular. In the parallel fusion pathway, DNA aligns with the membrane surface, showing very quick release of genetic material shortly after the initial fusion pore is formed. The perpendicular pathway also leads to transfection, but release is slower. We further show that the composition and size of the lipoplex, as well as the lipid composition of the endosomal membrane, have a significant impact on fusion efficiency in our models.
Highlights
Gene therapy is a promising technique with a wide applicability
After removing periodic boundary conditions and coating the aggregate with an additional layer of DOTAP and dioleoyl-snglycero-3- phosphoethanolamine (DOPE), we arrive at our small lipoplex model which proves stable during a 10 ms simulation (Figure 1I; Figure 1—figure supplements 1 and 2)
We compared the double-stranded DNA (dsDNA) spacing inside the solvated lipoplex with the available SAXS data from literature. This showed that the liquid crystal lattice of the inverted hexagonal phase in our solvated CG lipoplex was very close to the experimental data (6.0 ± 0.1 nm compared to 6.1 nm for SAXS) (Corsi et al, 2010)
Summary
Gene therapy is a promising technique with a wide applicability. Even though the concept of gene therapy has been around for a while, the problem remains to target and enter the right cells, without being toxic to the rest of the organism. Naked DNA gets quickly degraded in our body by exonucleases, whereas using viruses as vectors can lead to a strong acquired immune response (Nayak and Herzog, 2010). ‘new’ non-viral based vectors are being developed. Non-viral vectors have two advantages, first, they do not trigger a specific immune response, and second, they are potentially much cheaper than viral vectors. Most non-viral vectors use cationic lipids or polymers for complexation with the negatively charged DNA, concealing the genetic material from degradation. Lipoplexes are potentially toxic especially if they are highly positively charged (Huang and Li, 1997)
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