Absolute Quantification of Drug Vector Delivery to the Cytosol. Issue 27 (28th May 2021) - Lucchino, Marco
Abstract: Macromolecular drugs inefficiently cross membranes to reach their cytosolic targets. They require drug delivery vectors to facilitate their translocation across the plasma membrane or escape from endosomes. Optimization of these vectors has however been hindered by the difficulty to accurately measure cytosolic arrival. We have developed an exceptionally sensitive and robust assay for the relative or absolute quantification of this step. The assay is based on benzylguanine and biotin modifications on a drug delivery vector of interest, which allow, respectively, for selective covalent capture in the cytosol with a SNAP‐tag fusion protein and for quantification at picomolar sensitivity. The assay was validated by determining the absolute numbers of cytosolic molecules for two drug delivery vectors: the B‐subunit of Shiga toxin and the cell‐penetrating peptide TAT. We expect this assay to favor delivery vector optimization and the understanding of the enigmatic translocation process. Abstract : Macromolecular drug delivery vectors must translocate at the plasma membrane or escape from endosomes to reach the cytosol. This very inefficient process requires optimization, which is hindered by the difficulty to accurately measure cytosolic arrival. An exceptionally sensitive and robust assay to quantify this step was developed. The assay was validated by determining the absolute numbers of two macromolecular vectors reaching the cytosol.