Cell-penetrating peptides (CPPs) have been widely used for a cellular delivery of biologically relevant cargoes including antisense peptide nucleic acids (PNAs). Although chemical conjugation of PNA to a variety of CPPs significantly improves the cellular uptake of the PNAs, bioavailability (antisense activity) is still limited by endocytotic entrapment. We have shown that this low bioavailability can be greatly improved by combining CPP–PNA conjugate administration with a photochemical internalization technique using photosensitizers such as aluminum phthalocyanine (AlPcS2a ) or tetraphenylporphyrin tetrasulfonic acid (TPPS). Cellular uptake of the PNA conjugates were evaluated by using a sensitive cellular method with HeLa pLuc705 cells based on the splicing correction of luciferase gene by targeting antisense oligonucleotides to a cryptic splice site of the mutated luciferase gene. The cellular efficacy of CPP conjugates were evaluated by measuring luciferase activity as a result of splicing correction and was also confirmed by RT-PCR analysis of luciferase pre-mRNA.
