[1] [1] F. Heitz, M. C. Morris, G. Divita, "Twenty years of cell-penetrating peptides: From molecular mechanisms to therapeutics," Br. J. Pharmacol. 157, 195– 206 (2009).

[2] [2] P. M. Fischer, "Cellular uptake mechanisms and potential therapeutic utility of peptidic cell delivery vectors: Progress 2001–2006," Med. Res. Rev. 27, 755–795 (2007).

[3] [3] S. B. Fonseca, M. P. Pereira, S. O. Kelley, "Recent advances in the use of cell-penetrating peptides for medical and biological applications," Adv. Drug Deliv. Rev. 61, 953–964 (2009).

[4] [4] P. A. Wender, D. J. Mitchell, K. Pattabiraman, E. T. Pelkey, L. Steinman, J. B. Rothbard, "The design, synthesis, and evaluation of molecules that enable or enhance cellular uptake: Peptoid molecular transporters," Proc. Natl. Acad. Sci. USA 97, 13003–13008 (2000).

[5] [5] D. J. Mitchell, L. Steinman, D. T. Kim, C. G. Fathman, J. B. Rothbard, "Polyarginine enters cells more efficiently than other polycationic homopolymers," J. Pept. Res. 56, 318–325 (2000).

[6] [6] P. A. Wender, W. C. Galliher, E. A. Goun, L. R. Jones, T. H. Pillow, "The design of guanidiniumrich transporters and their internalization mechanisms," Adv. Drug Deliv. Rev. 60, 452–472 (2008).

[7] [7] I. A. Khalil, K. Kogure, S. Futaki, H. Harashima, "High density of octaarginine stimulates macropinocytosis leading to efficient intracellular traf- ficking for gene expression," J. Biol. Chem. 281, 3544–3551 (2006).

[8] [8] A. Mann, G. Thakur, V. Shukla, M. Ganguli, "Peptides in DNA delivery: Current insights and future directions," Drug Discov. Today 13, 152–160 (2008).

[9] [9] B. U. Samuel, B. Hearn, D. Mack, P. Wender, J. Rothbard, M. J. Kirisits, E. Mui, S. Wernimont, C. W. Roberts, S. P. Muench, D. W. Rice, S. T. Prigge, A. B. Law, R. McLeod, "Delivery of antimicrobials into parasites," Proc. Natl. Acad. Sci. USA 100, 14281–14286 (2003).

[10] [10] T. A. Aguilera, E. S. Olson, M. M. Timmers, T. Jiang, R. Y. Tsien, "Systemic in vivo distribution of activatable cell penetrating peptides is superior to that of cell penetrating peptides," Integr. Biol. 1, 371–381 (2009).

[11] [11] P. A. Wender, E. A. Goun, L. R. Jones, T. H. Pillow, J. B. Rothbard, R. Shinde, C. H. Contag, "Real-time analysis of uptake and bioactivatable cleavage of luciferin-transporter conjugates in transgenic reporter mice," Proc. Natl. Acad. Sci. USA 104, 10340– 10345 (2007).

[12] [12] K. Takayama, Y. Suehisa, T. Fujita, J. Nguyen, S. Futaki, A. Yamamoto, Y. Kiso, Y. Hayashi, "Oligoarginine-based prodrugs with self-cleavable spacers for Caco-2 cell permeation," Chem. Pharm. Bull. 56, 1515–1520 (2008).

[13] [13] J. B. Delehanty, I. L. Medintz, T. Pons, F. M. Brunel, P. E. Dawson, H. Mattoussi, "Self-assembled quantum dot-peptide bioconjugates for selective intracellular delivery," Bioconjug. Chem. 17, 920–927 (2006).

[14] [14] H. R gel, P. S lik, M. Hansen, ü. Langel,M. Pooga, "CPP-protein constructs induce a population of nonacidic vesicles during trafficking through endo-lysosomal pathway," J. Control. Release 139, 108–117 (2009).

[15] [15] E. A. Goun, R. Shinde, K. W. Dehnert, A. Adams- Bond, P. A. Wender, C. H. Contag, B. L. Franc, "Intracellular cargo delivery by an octaarginine transporter adapted to target prostate cancer cells through cell surface protease activation," Bioconjug. Chem. 17, 787–796 (2006).

[16] [16] J. P. Richard, K. Melikov, E. Vives, C. Ramos, B. Verbeure, M. J. Gait, L. V. Chernomordik, B. Lebleu, "Cell-penetrating peptides a reevaluation of the mechanism of cellular uptake," J. Biol. Chem. 278, 585–590 (2003).

[17] [17] F. Duchardt, M. Fotin-Mleczek, H. Schwarz, R. Fischer, R. Brock, "A comprehensive model for the cellular uptake of cationic cell-penetrating peptides," Traffic 8, 848–866 (2007).

[18] [18] I. Nakase, M. Niwa, T. Takeuchi, K. Sonomura, N. Kawabata, Y. Koike, M. Takehashi, S. Tanaka, K. Ueda, J. C. Simpson, A. T. Jones, Y. Sugiura, S. Futaki, "Cellular uptake of Arginine-rich peptides: Roles for macropinocytosis and actin rearrangement," Mol. Ther. 10, 1011–1022 (2004).

[19] [19] R. Fischer, M. Fotin-Mleczek, H. Hufnagel, R. Brock, "Break on through to the other side-biophysics and cell biology shed light on cell-penetrating peptides," ChemBioChem 6, 2126–2142 (2005).

[20] [20] E. A. Goun, T. H. Pillow, L. R. Jones, J. B. Rothbard, P. A. Wender, "Molecular transporters: Synthesis of oligoguanidinium transporters and their application to drug delivery and real-time imaging," ChemBioChem 7, 1497–1515 (2006).

[21] [21] C. Foerg, H. P. Merkle, "On the biomedical promise of cell penetrating peptides: Limits versus prospects," J. Pharm. Sci. 97, 144–162 (2008).

[22] [22] A. El-Sayed, S. Futaki, H. Harashima, "Delivery of macromolecules using arginine-rich cell-penetrating peptides: Ways to overcome endosomal entrapment," AAPS J. 11, 13–22 (2009).

[23] [23] M. M. Fretz, N. A. Penning, S. Al-Taei, S. Futaki, T. Takeuchi, I. Nakase, G. Storm, A. T. Jones, "Temperature-, concentration-and cholesteroldependent translocation of L-and D-octa-arginine across the plasma and nuclear membrane of CD34t leukaemia cells," Biochem. J. 403, 335–342 (2007).

[24] [24] R. M. Martin, G. Tünnemann, H. Leonhardt, M. C. Cardoso, "Nucleolar marker for living cells," Histochem. Cell Biol. 127, 243–251 (2007).

[25] [25] T. D. Mckee, J. Chen, I. Corbin, G. Zheng, R. Khokha, "Quantifying nanoparticle transport in vivo using hyperspectral imaging with a dorsal skinfold window chamber," J. Innov. Opt. Health. Sci. 5, 1250023 (2012).

[26] [26] J. Guo, Z. Fan, Z. Gu, X. Wei, "Studying the role of macrophages in circulating prostate cancer cells by in vivo flow cytometry," J. Innov. Opt. Health. Sci. 5, 1250027 (2012).

[27] [27] J. Qu, L. Liu, Y. Shao, H. Niu, B. Z. Gao, "Recent progress in multifocal multiphoton microscopy," J. Innov. Opt. Health. Sci. 5, 1250018 (2012).

[28] [28] M. Ranji, S. Nioka, H. N. Xu, B. Wu, L. Z. Li, D. L. Jaggard, B. Chance, "Fluorescent images of mitochondrial redox states in in situ mouse hypoxic ischemic intestines," J. Innov. Opt. Health Sci. 2, 365–374 (2009).

[29] [29] M. H llbrink, J. Oehlke, G. Papsdorf, M. Bienert, "Uptake of cell-penetrating peptides is dependent on peptide-to-cell ratio rather than on peptide concentration," Biochim. Biophys. Acta 1667, 222–228 (2004).

[30] [30] A. Manceur, A. Wu, J. Audet, "Flow cytometric screening of cell-penetrating peptides for their uptake into embryonic and adult stem cells," Anal. Biochem. 364, 51–59 (2007).

[31] [31] I. Massodi, G. L. Bidwell III, D. Raucher, "Evaluation of cell penetrating peptides fused to elastin-like polypeptide for drug delivery," J. Control. Release 108, 396–408 (2005).

[32] [32] T. Holm, H. Johansson, P. Lundberg, M. Pooga, M. Lindgren, ü. Langel, "Studying the uptake of cell-penetrating peptides," Nat. Protoc. 1, 1001– 1005 (2006).

[33] [33] J. R. Maiolo, M. Ferrer, E. A. Ottinger, "Effects of cargo molecules on the cellular uptake of argininerich cell-penetrating peptides," Biochim. Biophys. Acta Biomembr. 1712, 161–172 (2005).

[34] [34] A. Subtil, A. Hemar, A. Dautry-Varsat, "Rapid endocytosis of interleukin 2 receptors when clathrincoated pit endocytosis is inhibited," J. Cell Sci. 107, 3461–3468 (1994).

[35] [35] M. A. West, M. S. Bretscher, C. Watts, "Distinct endocytotic pathways in epidermal growth factorstimulated human carcinoma A431 cells," J. Cell Biol. 109, 2731–2739 (1989).

[36] [36] P. Keller, K. Simons, "Cholesterol is required for surface transport of influenza virus hemagglutinin," J. Cell Biol. 140, 1357–1367 (1998).

[37] [37] T. B. Potocky, A. K. Menon, S. H. Gellman, "Cytoplasmic and nuclear delivery of a TAT-derived peptide and a β-peptide after endocytic uptake into HeLa cells," J. Biol. Chem. 278, 50188–50194 (2003).

[38] [38] J. B. Rothbard, T. C. Jessop, P. A. Wender, "Adaptive translocation: The role of hydrogen bonding and membrane potential in the uptake of guanidinium-rich transporters into cells," Adv. Drug Deliv. Rev. 57, 495–504 (2005).

[39] [39] J. B. Rothbard, T. C. Jessop, R. S. Lewis, B. A. Murray, P. A. Wender, "Role of membrane potential and hydrogen bonding in the mechanism of translocation of guanidinium-rich peptides into cells," J. Am. Chem. Soc. 126, 9506–9507 (2004).

[40] [40] M. Kosuge, T. Takeuchi, I. Nakase, A. T. Jones, S. Futaki, "Cellular internalization and distribution of arginine-rich peptides as a function of extracellular peptide concentration, serum, and plasma membrane associated proteoglycans, Bioconjug. Chem. 19, 656–664 (2008).