Cell-penetrating peptides as delivery vectors for oligonucleotides and proteins Studies on applications and toxicity

Abstract: Cell-penetrating peptides (CPPs) have for a little bit more than a decade been employed as delivery vectors for a wide range of cargoes, ranging from gold particles to entire plasmids. Although CPP are well studied and utilized in numerous publications, our knowledge about CPP mediated transport is still poor. The articles presented in this thesis all consider different aspects of CPP mediated delivery. The first two papers are evaluating and improving already known techniques. In paper I, standard polyethyleneimine (PEI) transfection is improved by conjugating the CPP TP10 to the cationic polymer. In paper II, the same CPP is employed to deliver a dsDNA decoy oligo, resulting in decreased activity of the transcription factor c-Myc. The third paper is a more general overview of the delivery efficiency of well known CPPs and how the delivered cargo influences the CPP mediated toxicity. The study shows that different CPPs are suitable for different cargos and that toxic side effects depend heavily on the cargo and coupling strategy used. In Paper IV, a novel CPP, M918, is evaluated as a delivery vector for a transposon based non-viral gene therapy system. M918 display simultaneous delivery of a plasmid carrying a selection gene and a transposase into cultured cells. This is the first study where two so vastly different molecules as a cationic protein and an anionic plasmid, are simultaneously transported into cells by a peptide vector. The method might be a first step towards a safe peptide based non-viral gene therapy platform. Taken together, the results presented in this thesis might help to improve already existing techniques, increase our understandings about CPP mediated delivery and, at the same time, develop new CPP based delivery systems.