Thursday, October 17, 2013 3:30 pm - 3:30 pm EDT
Mousa Jafari, PhD
University of Waterloo
RNA interference is a post-transcriptional gene silencing process whereby short interfering RNAs (siRNAs) induce the sequence-specific degradation of complementary messenger RNA. Despite their promising therapeutic capabilities, siRNA-based strategies suffer from enzymatic degradation and poor cellular uptake. Several carrier-based approaches have been employed to enhance the stability and efficiency of siRNA delivery. Considering their safety, efficiency, and targeting capabilities, peptide-based delivery systems have shown great promise for overcoming the main obstacles in siRNA therapeutic delivery. Peptides are versatile and easily designed to incorporate a number of specific attributes required for efficient siRNA delivery.
This talk will focus on the design, characterization and utilization of a new class of amphipathic peptides for siRNA delivery. The study includes (i) designing amphipathic, amino acid pairing peptide sequences for siRNA delivery, (ii) in vitro experiments to evaluate transfection efficacy of the designed peptides, (iii) physicochemical characterization of the interaction between peptides and siRNA, and (iv) identification of the internalization pathway and kinetics of peptide-siRNA complexes.
Applying several biophysical, thermodynamic, spectroscopic and microscopic approaches, the interaction of peptide with siRNA was characterized. The designed peptides adopted a stable helical structure in saline or upon co-assembling with siRNA, forming nano-sized complexes. The complexes showed high gene knockdown efficiency with very limited cyto-toxicity. It was found that the electrostatic interaction of the peptide-siRNA complex with heparin sulphate proteoglycans at the cell surface is required to trigger the uptake process. Using endocytic inhibitors, a size-dependent cellular uptake mechanism of the complexes was revealed. This work provides essential information for peptide design and characterization in the development of peptide-based siRNA delivery.