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Cell-penetrating peptides provide a promising strategy for delivery of drugs across the blood-brain barrier. Here, we present an overview of CPP and peptide-mediated delivery to the central nervous system as well as a Transwell in vitro model to evaluate passage across an endothelial cell layer mimic of the blood-brain barrier.

Cell-penetrating peptides are peptides capable of translocating the cellular membrane and entering the cell, either alone or together with a cargo. Potential applications of cell-penetrating peptides include drug delivery and gene therapy. This thesis is focused on the development of novel cell-penetrating peptides and applications for passage across the blood-brain barrier. We have developed a series of novel cell-penetrating peptides based on the model amphipathic peptide and modifications developed for the PepFect peptides. Our general goal is to improve our understanding of the structural requirements for efficient cell penetration and to apply this knowledge in the development of improved cell-penetrating peptides. We have also developed an in vitro model of the blood brain barrier based on brain endothelial cells grown on a semi-permeable membrane. This model has been used together with a series of novel peptides modified with targeting sequences in order to study the passage of peptides across the barrier and into an underlying layer of glioma cells., At the time of the seminar, the papers were not published and had a status as follows: Paper 1: Accepted; Paper 2: Epub ahead of print.

The field of gene therapy is starting to move towards clinical applications but is currently limited by the lack of efficient delivery systems. Cell-penetrating peptides provide a means of cellular delivery for gene therapy applications as well as delivery of traditional drugs. Using cell-penetrating peptides a range of different cargos have been successfully delivered into a number of cell types, in vitro as well as in vivo. In this review we discuss uptake mechanisms of different cell-penetrating peptides, with or without cargo. The transition from in vitro to in vivoapplications and strategies to increase the bioavailability of cell-penetrating peptides are also discussed.

Cell-penetrating peptides provide a highly promising strategy for intracellular drug delivery. One relevant clinical application of cell-penetrating peptides is cancer therapeutics. Peptide based delivery could increase the uptake of drugs in tumor cells and thereby increase the efficacy of the treatment, either of conventional small molecular drugs or oligonucleotide based therapeutics. This review is focused on the cancer applications of cell penetrating peptides as delivery systems; different aspects of drug loading, cargoes and delivery are discussed together with methods for targeted delivery, activatable cell-penetrating peptides and transducible agents coupled to cell-penetrating peptides.