Cell-penetrating peptide based nanocomplexes for oligonucleotide delivery

Oligonucleotide-based drugs hold great promise for the treatment of many types of diseases, ranging from genetic disorders to viral infections and cancer. The problem is that efficient delivery across the cell membrane is required for oligonucleotides to have their desired effect. Cell-penetrating peptides (CPPs) provide a solution to this problem. CPPs are capable of transporting cargoes such as drugs or nucleic acids for gene therapy into the cell, either by covalent conjugation to the cargo or by non-covalent complex formation. This thesis is focused on the development of a class of peptides called PepFects, peptides with fatty acid modifications capable of forming nanoparticle-sized complexes with oligonucleotides. These complexes are efficiently internalized by many different cell types and are generally non-toxic and non-immunogenic. We have developed a number of novel PepFect peptides and a quantitative structure-activity model to predict the biological effect of our peptides. In addition, the involvement of scavenger receptors class A in the endocytic uptake of PepFect complexes as well as other CPPs and polymeric transfection agents was studied. Lastly, we have developed a series of PepFect peptides for delivery across the blood-brain barrier and a model system mimicking the blood-brain barrier in order to evaluate the passage of these peptides. The general aim of this thesis is to improve the understanding of intracellular delivery of oligonucleotides with PepFect peptides from both a chemical and a biological viewpoint, and further improve the efficacy of this delivery system with the long-term goal of making it useful in clinical settings.