Søndergaard, Rikke Vicki1; Mattebjerg, Maria Ahlm4; Henriksen, Jonas Rosager6; Moghimi, S Moein8; Andresen, Thomas Lars1
1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Colloids and Biological Interfaces, Department of Micro- and Nanotechnology, Technical University of Denmark3 Center for Nanomedicine and Theranostics, Center, Technical University of Denmark4 National Food Institute, Technical University of Denmark5 Division of Industrial Food Research, National Food Institute, Technical University of Denmark6 Department of Chemistry, Technical University of Denmark7 Physical and Biophysical Chemistry, Department of Chemistry, Technical University of Denmark8 unknown
Polycations such as polyethylenimine (PEI) are used in many novel nonviral vector designs and there are continuous efforts to increase our mechanistic understanding of their interactions with cells. Even so, the mechanism of polyplex escape from the endosomal/lysosomal pathway after internalization is still elusive. The "proton sponge " hypothesis remains the most generally accepted mechanism, although it is heavily debated. This hypothesis is associated with the large buffering capacity of PEI and other polycations, which has been interpreted to cause an increase in lysosomal pH even though no conclusive proof has been provided. In the present study, we have used a nanoparticle pH sensor that was developed for pH measurements in the endosomal/lysosomal pathway. We have carried out quantitative measurements of lysosomal pH as a function of PEI content and correlate the results to the "proton sponge " hypothesis. Our measurements show that PEI does not induce change in lysosomal pH as previously suggested and quantification of PEI concentrations in lysosomes makes it uncertain that the "proton sponge " effect is the dominant mechanism of polyplex escape.Molecular Therapy (2012); doi:10.1038/mt.2012.185.
Molecular Therapy, 2013, Vol 21, Issue 1, p. 149-157