CPP or cholesterol conjugation to antisense PNA for cellular delivery

Peptide nucleic acids (Proc Nat Acad Sci USA) are DNA mimics consisting of the four common bases as in DNA on a pseudopeptide backbone that makes them extremely stable in biological fluids. Antisense PNA can be targeted to mRNA in the cytoplasm in a complementary base pairing manner. In order to achieve efficient mRNA based targeting, endosomal release or direct uptake of Proc Nat Acad Sci USA into the cytosol is mandatory. However, relatively poor internalization of these agents is reported for most cells. 1 Several reports suggested cell penetrating peptide (CPP) based delivery systems for PNA delivery into cells. 2 Unfortunately, endosomal capture seems to be a major challenge in these approaches restricting the ability of PNA to bind with mRNA. Recent studies have explored the use of cholesterol-siRNA conjugates to enhance cellular import. 3 In order to attain efficient PNA internalization into cells, we synthesized two different sequences of cholesterol coupled antisense PNA and evaluated their uptake efficacy in comparison to a PNA-CPP conjugate previously reported by our group