Cytosolic delivery from endosomes is critical for those drugs that are susceptible to attack by lysosomal
enzymes, such as
DNA,
RNA,
oligonucleotides,
proteins and
peptides. Therefore, we have designed pH-sensitive, membrane-disruptive
polymers to enhance the release of drugs from the acidic endosomal compartment to the cytoplasm. We have found that one
polymer in particular, poly(propylacrylic
acid) (
PPAA), is very effective at membrane disruption at pHs below 6.5, based on
hemolysis studies.
PPAA also significantly enhances in vitro transfections of lipoplex formulations in cell culture, and does so in the presence of as much as 50% serum. In this study, we have extended our in vitro
hemolysis and cell culture studies to an in vivo murine excisional wound healing model. A pilot study with a
green fluorescent protein (GFP)-encoding plasmid indicated that injection of formulations containing
PPAA into healing
wounds resulted in increased GFP expression. Subsequently, by administering sense and
antisense DNA for the
angiogenesis inhibitor thrombospondin-2 (TSP2), we were able to alter the wound healing response in TSP2-null and wild type mice, respectively. Our findings showed that when
PPAA was added to lipoplex formulations, expression of TSP2 was enhanced in TSP2-null mice compared to control formulations. These results show that
PPAA can enhance in vivo transfections and that inhibition of TSP2 expression may lead to improved wound healing. These results suggest that
PPAA can provide significant improvements in the in vivo efficacy of drugs such as
DNA.