Facing a camera, Daniel Abegg (biochemist, PhD student in Adibekian lab, UNIGE) presents his recent work and gives emphasis on the biochemical problem behind it. Eline Bartolami (chemist, postdoc in Matile lab, UNIGE) comments with a few lines to explain the chemical approach used to solve the problem. They are from different disciplines but meet through chemical biology.

 

Perspective by Eline Bartolami

To ensure efficient cellular uptake and intracellular distribution of cargos, chemists and biochemists have developed various drug delivery systems. Among them, a new method based on strained cyclic disulfides has recently shown promising results for cell membrane penetration. Thiol-mediated uptake generates dynamic covalent bonds with the thiols present on the cell surface. It has been shown that fluorescent carboxyfluorescein dye could passively cross the cell membrane when attached to a small strained cyclic disulfide. This process of internalization is enhanced by increasing the disulfide ring tension: we have used asparagusic acid with a CSSC dihedral angle of 27° to ensure the intracellular distribution of fully unprotected peptides.

Two fluorescent probes were synthesized to study the molecular mechanism of the cellular uptake. The one presenting the asparagusic acid tag (AspA tag) was found to covalently bind the cysteines on live cells compared to the free tag. Proteomic studies made with the second probe proved the formation of covalent bonds between the asparagusic acid and two cysteine residues on the surface of the transferrin receptor. The resulting mechanism of uptake of the small size tag was determined to be endocytic. Finally, the cargo remained functional after uptake as shown by long BH3 domain peptides successfully delivered by simple attachment of the AspA tag that were still able to induce apoptotic response in cancer cells.

 

Go Further

Abegg D., Gasparini G., Hoch D. G., Shuster A., Bartolami E., Matile S., Adibekian A., “Strained Cyclic Disulfides Enable Cellular Uptake by Reacting with the Transferrin Receptor”, J. Am. Chem. Soc., 2017, 139, 231–238. Read the publication