Uptake Kinetics of Cell-Penetrating Peptides
As our knowledge increases about the diversity in uptake mechanisms displayed by cell-penetrating peptides (CPP), the concept of CPP uptake kinetics becomes increasingly complex. Here, we present three different assays that can be used for studying different kinetic aspects of CPP-mediated delivery: intracellular accumulation and membranolytical effects, intracellular CPP-cargo detachment, and finally a functional readout of a biological action from the delivered cargo. Unlike the traditional end-point measurements that give a static postincubation readout, these assays are all dynamic, real-time, in situ measurements obtained during incubation. A combination of some (or all) of these different assays gives us not only interesting kinetic information about the uptake routes but also provides a simple and valuable methodology for the evaluation of potential drug candidates based on the chemical modification of CPPs by cargo attachment.
Key wordsCPP uptake Kinetics Flow cytometry Fluorescence Bioluminescence Fluorescence quenching
The work presented in this article was supported by: the Swedish Research Council (VR-NT); the Center for Biomem brane Research, Stockholm; the Knut and Alice Wallenberg’s Foundation; the EU through the European Regional Development Fund through the Center of Excellence in Chemical Biology, Estonia; the targeted financing SF0180027s08 from the Estonian Government; the DoRa Program of The European Social Fund; and the Archimedes Foundation.