Various properties of polymeric carriers improved the transfection efficiency

In order to develop novel efficient gene carriers, we have been focusing on the transcription of transgene in the nucleus among various steps in the gene transfer system. Optimal carrier properties for improving the transgene recognition by transcription factors have not been clarified so far. In the present study, we established a novel evaluation system for the intranuclear transcription efficiency of the transgene using microinjection technique. Polyplexes composed of polypeptides with different molecular weights were microinjected into the cytoplasm or nucleus of COS-1 cells, and the relationship between the carrier properties, such as molecular weight, and the intranuclear transcription efficiency was evaluated. The molecular weight (Mw) dependency of the transgene transcription in the living cells was successfully quantified, and the low Mw polymers were found not to suppress the transcription but high Mw polymers allowed almost no transcription. Interestingly, the transcription efficiencies of poly(arginine) (PR) and poly(lysine) (PK) were almost same although the PR is widely reported to be more efficient gene carrier than PK. The difference in the various properties and intracellular trafficking of PR/DNA and PK/DNA polyplexes will be discussed.