STABILITY OF LIPID DNA COMPLEXES DURING AGITATION AND FREEZE-THAWING/

It is well established that cationic liposomes facilitate the delivery of DNA and offer substantial advantages over viral-based delivery sys tems. However, these synthetic vectors readily aggregate in liquid for mulations which in clinical trials requires preparation of lipid/DNA c omplexes at the bedside immediately before injection. This temporal re quirement could be eliminated if complexes were formulated as stable p reparations that could be shipped, stored, and administered as needed. To this end, our study investigates the stability of lipid/DNA comple xes during physical stresses that might be encountered during shipping and storage, i.e., agitation and freeze-thawing. Our data show that a gitation significantly reduces transfection rates in complexes prepare d with three different commercially available lipid formulations. Addi tional experiments indicate that slow freezing is more damaging than r apid freezing, and that sucrose is able to preserve transfection and c omplex size during freeze-thawing. These results are consistent with p revious reports and demonstrate that frozen formulations may be suitab le for maintaining transfection rates of lipid/DNA complexes. Under ce rtain conditions, we observe a reproducible 3-fold increase in transfe ction after freeze-thawing that is prevented by high concentrations of sucrose. Together, these data suggest that physical stresses can alte r structural characteristics of lipid/DNA complexes that can markedly affect rates of DNA delivery.