Annealing of pDNA to Form the Single-Nucleobase-Terminal Complex for In Vivo Gene Expression

Although complexes with polycationic carriers have been proposed for the skeletal muscle delivery of plasmid DNA (pDNA), there is a problem in reducing the effect due to nonspecific aggregation in vivo caused by multiple cationic charges. Therefore, we have synthesized a thymine end-modified poly(ethylene glycol) (Thy-PEG) as a potentially nonionic single-nucleobase end-modified PEG and designed to form a complex by hydrogen bonding with pDNA whose duplex was partially dissociated by annealing. Then, the local administration of the resulting Thy-PEG/pDNA complex with a PEG chain length of 5k and a [Thy]_Thy-PEG/[Base]_pDNA ratio of 0.5 to the tibialis muscle of mice resulted in a tendency for a 14-fold increase in expression, as compared to that of annealed naked pDNA. In this study, the created Thy-PEG/pDNA complexes, that is, single-nucleobase-terminal complexes (SNTCs), can offer a unique cation-free pDNA delivery platform in vivo.