Tetraiodothyroacetic acid-conjugated polyethylenimine for integrin receptor mediated delivery of the plasmid encoding IL-12 gene

Abstract

Targeted delivery by polymer-based nanoparticles has been considered as an efficient approach to transfer genetic materials into cells. Considering the over expression of integrin α_Vβ₃ receptor on tumor cells and the presence of the binding site for tetraiodothyroacetic acid (tetrac) on integrin receptor, we hypothesized that the conjugation of tetrac to polyethylenimine (PEI) might be an effective strategy for pDNA delivery into the cells over-expressing integrins on their surfaces. In order to test the hypothesis, tetrac conjugated PEI/plasmid DNA complexes were prepared and their ability in the delivery of plasmid encoding IL-12 gene was investigated. Moreover, the conjugates were characterized with respect to plasmid DNA condensation ability, particle size and zeta potential as well as cell-induced toxicity and plasmid protection against DNase degradation. The results demonstrated that tetrac conjugated derivatives of PEI were able to condense the plasmid and protect it against enzyme degradation. The results of dynamic light scattering (DLS) and atomic force microscopy (AFM) revealed that the formed nanoparticles were in the size range of 85-125nm. The highest level of IL-12 gene expression was achieved by terac-conjugated PEIs at the carrier to plasmid ratio of 8 where they could increase the level of gene expression up to 4 fold in the cell lines over-expressing integrin α_Vβ₃ receptor whereas no increase in the level of IL-12 expression in the cell lines lacking integrin receptors was observed. Also, the results of the competitive inhibition of the receptors demonstrated the specificity of transfection for the cells over expressing α_vβ₃ receptor. On the other hand, tetrac conjugation of PEI significantly reduced the polymer-induced apoptotic effects. The results obtained in this investigation suggest the potential of tetrac as a small molecule mimicking the binding properties of integrin binding peptides (e.g., RGD) for targeted gene delivery.

Keywords: Gene delivery; Integrin; Interleukin-12; Polyethylenimine; Targeted delivery.