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The Primary Mechanism of Cellular Internalization for a Short Cell- Penetrating Peptide as a Nano-Scale Delivery System

[ Vol. 18 , Issue. 7 ]


Betty R. Liu*, Yue-Wern Huang, Mallikarjuna Korivi, Shih-Yen Lo, Robert S. Aronstam and Han-Jung Lee   Pages 569 - 584 ( 16 )


Background: Development of effective drug delivery systems (DDS) is a critical issue in health care and medicine. Advances in molecular biology and nanotechnology have allowed the introduction of nanomaterial-based drug delivery systems. Cell-penetrating peptides (CPPs) can form the basis of drug delivery systems by virtue of their ability to support the transport of cargoes into the cell. Potential cargoes include proteins, DNA, RNA, liposomes, and nanomaterials. These cargoes generally retain their bioactivities upon entering cells.

Method: In the present study, the smallest, fully-active lactoferricin-derived CPP, L5a is used to demonstrate the primary contributor of cellular internalization.

Results: The secondary helical structure of L5a encompasses symmetrical positive charges around the periphery. The contributions of cell-specificity, peptide length, concentration, zeta potential, particle size, and spatial structure of the peptides were examined, but only zeta potential and spatial structure affected protein transduction efficiency. FITC-labeled L5a appeared to enter cells via direct membrane translocation insofar as endocytic modulators did not block FITC-L5a entry. This is the same mechanism of protein transduction active in Cy5 labeled DNA delivery mediated by FITC-L5a. A significant reduction of transduction efficiency was observed with structurally incomplete FITC-L5a formed by tryptic destruction, in which case the mechanism of internalization switched to a classical energydependent endocytosis pathway.

Conclusion: These results support the continued development of the non-cytotoxic L5a as an efficient tool for drug delivery.


Cell-penetrating peptides (CPPs), cellular internalization, direct membrane translocation, drug delivery system (DDS), lactoferricin, helical wheel projection, protein transduction domains (PTDs).


Department of Laboratory Medicine and Biotechnology, Collage of Medicine, Tzu Chi University, Hualien 97004, Department of Biological Sciences, Missouri University of Science and Technology, Rolla, MO 65409-1120, College of Physical Education and Health Sciences, Zhejiang Normal University, Jinhua, Zhejiang, Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien 97004, College of Science and Technology, Bloomsburg University of Pennsylvania, Bloomsburg, PA17815-1301, Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien 97401

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