Selecting improved peptidyl motifs for cytosolic delivery of disparate protein and nanoparticle materials

ACS Nano. 2013 May 28;7(5):3778-96. doi: 10.1021/nn400702r.


Cell penetrating peptides facilitate efficient intracellular uptake of diverse materials ranging from small contrast agents to larger proteins and nanoparticles. However, a significant impediment remains in the subsequent compartmentalization/endosomal sequestration of most of these cargoes. Previous functional screening suggested that a modular peptide originally designed to deliver palmitoyl-protein thioesterase inhibitors to neurons could mediate endosomal escape in cultured cells. Here, we detail properties relevant to this peptide's ability to mediate cytosolic delivery of quantum dots (QDs) to a wide range of cell-types, brain tissue culture and a developing chick embryo in a remarkably nontoxic manner. The peptide further facilitated efficient endosomal escape of large proteins, dendrimers and other nanoparticle materials. We undertook an iterative structure-activity relationship analysis of the peptide by discretely modifying key components including length, charge, fatty acid content and their order using a comparative, semiquantitative assay. This approach allowed us to define the key motifs required for endosomal escape, to select more efficient escape sequences, along with unexpectedly identifying a sequence modified by one methylene group that specifically targeted QDs to cellular membranes. We interpret our results within a model of peptide function and highlight implications for in vivo labeling and nanoparticle-mediated drug delivery by using different peptides to co-deliver cargoes to cells and engage in multifunctional labeling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Cell-Penetrating Peptides / chemistry*
  • Cell-Penetrating Peptides / metabolism
  • Chick Embryo
  • Cytosol / metabolism*
  • Drug Carriers / chemistry*
  • Drug Carriers / metabolism
  • Endosomes / metabolism
  • Humans
  • Maltose-Binding Proteins / metabolism*
  • Molecular Sequence Data
  • Quantum Dots*


  • Cell-Penetrating Peptides
  • Drug Carriers
  • Maltose-Binding Proteins