Self-catalyzed degradable cationic polymer for release of DNA.

The controlled release of siRNA or DNA complexes from cationic polymers is an important parameter design in polymer-based delivery carriers. In this work, we use the self-catalyzed degradable poly(2-dimethylaminoethyl acrylate) (PDMAEA) to strongly bind, protect, and then release oligo DNA (a mimic for siRNA) without the need for a cellular or external trigger. This self-catalyzed hydrolysis process of PDMAEA forms poly(acrylic acid) and N,N'-dimethylamino ethyl ethanol, both of which have little or no toxicity to cells, and offers the advantage of little or no toxicity to off-target cells and tissues. We found that PDMAEA makes an ideal component of a delivery carrier by protecting the oligo DNA for a sufficiently long period of time to transfect most cells (80% transfection after 4 h) and then has the capacity to release the DNA inside the cells after ~10 h. The PDMAEA formed large nanoparticle complexes with oligo DNA of ~400 nm that protected the oligo DNA from DNase in serum. The nanoparticle complexes showed no toxicity for all molecular weights at a nitrogen/phosphorus (N/P) ratio of 10. Only the higher molecular weight polymers at very high N/P ratios of 200 showed significant levels of cytotoxicity. These attributes make PDMAEA a promising candidate as a component in the design of a gene delivery carrier without the concern about accumulated toxicity of nanoparticles in the human body after multiadministration, an issue that has become increasingly more important.