Interactions between PEI and biological polyanions and the ability of glycosaminoglycans in destabilizing...

The lack of understanding of polyplexes stability and their dissociation mechanisms, allowing the release of DNA, is currently a major limitation in non-viral gene delivery. One proposed mechanism for DNA-based polyplexes dissociation is based on the electrostatic interactions between polycations and biological polyanions, such as glycosaminoglycans (GAGs). This work aimed at investigating whether GAGs such as heparin, chondroitin sulphate and hyaluronic acid promote the dissociation of PEI/DNA polyplexes. We studied the electrostatic complexation between branched poly(ethyleneimine) (b-PEI₂₅) and polyanions (model DNA and GAGs) through conductivity and ζ-potential measurements. The formation of b-PEI₂₅/polyanion polyplexes through electrostatic interactions was analyzed in depth, providing key insights into charge stoichiometry, morphology, thermodynamics and physicochemical characteristics. The stability of polyplexes was tested in the presence of the different GAGs. Heparin was found to be the only polyanion capable of releasing peGFP-C3 plasmid from polyplexes, complexing stoichiometrically with the free b-PEI₂₅ in excess, before releasing the plasmid. The ability of GAGs to disrupt polyplexes and release DNA was correlated with the thermodynamic characteristics of b-PEI₂₅/polyanions complexation. Our findings indicate that heparin's strong interaction with PEI and its high charge density, compared to other GAGs and polyanions, are pivotal in determining complex stability and promoting DNA release.