Molecular Architecture Governs Cytotoxicity and Gene Transfection Efficacy of Polyethylenimine Based Nanoplexes in Mammalian Cell Lines

Finding the ideal polyethylenimine-plasmid DNA system for co-delivery of payloads in cancer therapy

Researchers still hold for the development of a safety and advanced delivery system able of efficient therapeutic action. The co-delivery of different payloads is part of this strategy and has already demonstrated to be a valuable tool against the most severe diseases. In the pursuit of an "ideal" drug/gene co-delivery vector for cancer therapy, we present a complete comparison study of different morphology and molecular weight polyethylenimine (PEI)/p53 encoding plasmid DNA (pDNA) polyplexes. Besides pDNA, also methotrexate (MTX) has been loaded into PEI/pDNA nanoparticles. The polyplexes have been characterized in terms of morphology, size, surface charges, loading/encapsulation efficiencies and toxicity. Although the nature of PEI can influence these properties, they deeply vary with the polymer nitrogen to pDNA phosphate (N/P) ratio. The transfection of HeLa cells mediated by PEI/pDNA/MTX vectors leads to both the release of MTX and the p53 protein expression. Modelling of MTX release kinetics brings valuable information concerning drug delivery mechanism. Moreover, the success of transfection is dependent on the nature of PEI and, mainly, on the N/P ratio used in the formulation of polyplexes. This work represents a great contribution for the design and development of innovative PEI based carriers for the most challenging biomedical applications.

Atomic-Scale Molecular Dynamics Simulations of DNA-Polycation Complexes: Two Distinct Binding Patterns

Synthetic cationic polymers represent a promising class of delivery vectors for gene therapy. Here, we employ atomistic molecular dynamics simulations to gain insight into the structure and properties of complexes of DNA with four linear polycations: polyethylenimine (PEI), poly-l-lysine (PLL), polyvinylamine (PVA), and polyallylamine (PAA). These polycations differ in their polymer geometries, protonation states, and hydrophobicities of their backbone chains. Overall, our results demonstrate for the first time the existence of two distinct patterns of binding of DNA with polycations. For PEI, PLL, and PAA, the complex is stabilized by the electrostatic attraction between protonated amine groups of the polycation and phosphate groups of DNA. In contrast, PVA demonstrates an alternative binding pattern as it gets embedded into the DNA major groove. It is likely that both the polymer topology and affinity of the backbone chain of PVA to the DNA groove are responsible for such behavior. The differences in binding patterns can have important biomedical implications: embedding PVA into a DNA groove makes it less sensitive to changes in the aqueous environment (pH level, ionic strength, etc.) and could therefore hinder the intracellular release of genetic material from a delivery vector, leading to lower transfection activity.