A bifurcated proteoglycan binding small molecule carrier for siRNA delivery.
Bottom Line: A wider application of siRNA- and miRNA- based therapeutics is restricted by the currently available delivery systems.We have designed a new type of small molecule carrier (SMoC) system for siRNA modeled to interact with cell surface proteoglycans.This bifurcated SMoC has similar affinity for the model proteoglycan heparin to an equivalent polyarginine peptide and exhibits significant mRNA knockdown of protein levels comparable to lipofectamine and the previously reported linear SMoC.
Affiliation: The Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT, UK.Show MeSH
Mentions: We previously described that the small molecule carrier (SMoC) class of compounds, which are small molecule mimics of penetratin, show potential as siRNA delivery agents 22, showing similar levels of gene silencing in IMR-90 cells to the commonly used transfection reagent Lipofectamine®. SMoCs possess cationic guanidine groups linked to a biphenyl backbone, forming amphipathic alpha-helix mimics which are capable of crossing cell membranes 23, 24. We postulated that the positive charges may be partially stabilized by π-cation interactions with the biphenyl backbone to promote electrostatic binding to siRNA and to anionic cell surface proteoglycans. The most successful SMoC compound for siRNA transfection described thus far is 4G-SMoC-SSPy 1, (Figure 1, see Figure S1 for the naming convention for SMoCs). In the present study, we hypothesized that a bifurcated SMoC compound, 4G-BfSMoC-COOH, 2 would achieve the twin aims of cell surface proteoglycan binding and more flexible chemical synthesis. We observed that 2 retains the ability to complex and deliver siRNA, resulting in knockdown of the cell cycle gene cdc7. 4G-BfSMoC-COOH, 2 and other SMoCs show significant binding to heparin as a model for cell surface proteoglycans. 2 is easily synthesized and includes a central chemical ‘handle’ that will allow covalent attachment to other biomolecules.
Affiliation: The Wolfson Institute for Biomedical Research, UCL, Gower Street, London, WC1E 6BT, UK.