Plasmid DNA Mono-Ion Complex for in Vivo Sustainable Gene Expression

Structure-Activity Relationship of Mono-Ion Complexes for Plasmid DNA Delivery by Muscular Injection

The structure-activity relationship of mono-ion complexes (MICs) for plasmid DNA (pDNA) delivery by muscular injection is demonstrated. MICs were formed between pDNA and monocationic poly(ethylene glycol) (PEG) macromolecules. As monocationic PEGs, the ω-amide-pentylimidazolium (APe-Im) end-modified PEGs with a stable amide (Am) and hydrolytic ester (Es) bond, that is, APe-Im-Am-PEG and APe-Im-Es-PEG, respectively, are synthesized. The difference between the APe-Im-Am-PEG and APe-Im-Es-PEG was only a spacer structure between a terminal cation and a PEG chain. The resulting pDNA MICs with APe-Im-Am-PEG at a charge ratio (+/-) of 32 or 64 were more stable than those with APe-Im-Es-PEG in the presence of serum proteins. The highest gene expression by muscular injection was achieved using the APe-Im-Am-PEG/pDNA MIC at a charge ratio (+/-) of 32 with a smaller particle diameter of approximately 50 nm, as compared to that charge ratio of 64. Consequently, the pDNA MIC with the monocationic PEG with a stable amide spacer, as compared to a hydrolytic ester spacer, is considered to be suitable for the highest gene expression by muscular injection.

Noncorrelative relation between in vitro and in vivo for plasmid DNA transfection by succinylated polyethylenimine muscular injection

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.