536. Charge Switchable Helper Lipids for Gene Delivery

Abstract

The current gene delivery approaches in use include viral vectors, synthetic cationic vectors, or physical methods such as electroporation or gene gun. Of these, synthetic cationic vectors offer the advantages of low toxicity, nonimmunogenicity, large nucleic acid payloads, and ease of synthesis; but suffer from low transfection activities. This low activity likely reflects inefficiencies in the overall transfection pathway that includes DNA-synthetic vector complexation, endocytosis, endosomal escape, nuclear entry, and finally expression. Today synthetic cationic vectors are used in conjunction with |[ldquo]|helper|[rdquo]| phospholipids to obtain greater gene transfection levels. The helper lipids are typically zwitterionic lipids such as dioleylphosphatidyl choline (DOPC) or dioleylphosphatidyl ethanolamine (DOPE). These lipids promote fusion with the membrane of the endosome, which leads to the disruption of the endosome and release of the DNA, increasing transfection efficacy. Fortunately, several research groups have recognized the importance of designing and evaluating new synthetic vectors that respond to local environmental effects in an effort to increase gene transfection efficiency. To determine if a charge-reversal or charge-switchable concept translates to a more efficient helper phospholipid, we prepared a zwitterionic charge-switchable phospholipid. Herein, we describe the synthesis and characterization of a functional phospholipid that undergoes an electrostatic transition from neutral to di-anionic that shows enhanced gene transfection when used with DOTAP. (See Figure)