The polyion complexes (PICs) between plasmid DNA (pDNA) and succinylated branched polyethylenimine (bPEI-Et-COOH) were formed for in vivo pDNA delivery by muscular injection. Transmission electron microscopy (TEM) observation revealed that the PIC between pDNA and bPEI-Et-COOH with higher succinylated degree formed the particle structure with corona-like shell. Furthermore, confocal laser scanning microscopy (CLSM) observation revealed that pDNAs were successfully delivered inside the cells and that the pDNAs were colocalized with the nuclei of the cells after endosomal escape. Although the pDNA/bPEI-Et-COOH PICs mediated significant gene expression in vitro, the PICs did not mediate gene expression in vivo muscular injection. Consequently, the pDNA transfection by bPEI-Et-COOH was noncorrelative between in vitro and in vivo in spite of low toxicity by succinylation both in vitro and in vivo. The noncorrelative relation between in vitro and in vivo for pDNA transfection by bPEI-Et-COOH muscular injection would be considerable design for pDNA carriers in vivo.
Keywords: in vivo transfection; pDNA delivery; polyion complex; succinylated branched polyethylenimine.