Tat peptide is capable of importing large nanoparticles across nuclear membrane in digitonin permeabilized cells

Understanding the capabilities and limitations of nuclear import is crucial to efficient delivery of macromolecules and nanoparticles for diagnosis and targeted therapy of diseases. Here we report the Tat peptide-mediated import of different cargos into cell nucleus, including dye-labeled streptavidin protein, 43 and 90 nm fluorescent beads, as well as approximately 20 nm quantum dots for kinetic measurements. Our results revealed significant differences between Tat- and NLS-mediated nuclear import: unlike delivery with the NLS, Tat peptide-based delivery is not inhibited by WGA blockage nor does it require ATP. Surprisingly, Tat peptide was able to import 90 nm beads into the nuclei of digitonin-permeabilized cells, suggesting that its interaction with the nuclear envelope follows a mechanism different from that of NLS. The import kinetics was quantified using Tat peptide-conjugated QDs, yielding a kinetic constant of 0.0085 s(-1). Taken together, our results suggest that, compared with NLS, Tat peptide-mediated nuclear import is faster, follows a different pathway, and is capable of importing large nanoparticles. These results have significant implications for the development of new approaches for delivery of cargo into the nuclei of living cells.