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Selective uptake of single-walled carbon nanotubes by circulating monocytes for enhanced tumour delivery


In cancer imaging, nanoparticle biodistribution is typically visualized in living subjects using ‘bulk’ imaging modalities such as magnetic resonance imaging, computerized tomography and whole-body fluorescence. Accordingly, nanoparticle influx is observed only macroscopically, and the mechanisms by which they target cancer remain elusive. Nanoparticles are assumed to accumulate via several targeting mechanisms, particularly extravasation (leakage into tumour). Here, we show that, in addition to conventional nanoparticle-uptake mechanisms, single-walled carbon nanotubes are almost exclusively taken up by a single immune cell subset, Ly-6Chi monocytes (almost 100% uptake in Ly-6Chi monocytes, below 3% in all other circulating cells), and delivered to the tumour in mice. We also demonstrate that a targeting ligand (RGD) conjugated to nanotubes significantly enhances the number of single-walled carbon nanotube-loaded monocytes reaching the tumour (P < 0.001, day 7 post-injection). The remarkable selectivity of this tumour-targeting mechanism demonstrates an advanced immune-based delivery strategy for enhancing specific tumour delivery with substantial penetration.

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Figure 1: SWNT uptake into circulating cells.
Figure 2: Flow cytometry plots showing selective uptake of SWNTs into a blood monocyte subset.
Figure 3: SWNT-laden monocytes enter the tumour interstitium in a peptide-dependent manner.


  1. 1

    Maeda, H. The link between infection and cancer: tumor vasculature, free radicals, and drug delivery to tumors via the EPR effect. Cancer Sci. 7, 779–789 (2013).

    Article  Google Scholar 

  2. 2

    Hirsjarvi, S., Passirani, C. & Benoit, J. P. Passive and active tumour targeting with nanocarriers. Curr. Drug Disc. Technol. 8, 188–196 (2011).

    CAS  Article  Google Scholar 

  3. 3

    Holgado, M. A., Martin-Banderas, L., Alvarez-Fuentes, J., Fernandez-Arevalo, M. & Arias, J. L. Drug targeting to cancer by nanoparticles surface functionalized with special biomolecules. Curr. Med. Chem. 19, 3188–3195 (2012).

    CAS  Article  Google Scholar 

  4. 4

    Yu, M. K., Park, J. & Jon, S. Targeting strategies for multifunctional nanoparticles in cancer imaging and therapy. Theranostics 2, 3–44 (2012).

    CAS  Article  Google Scholar 

  5. 5

    Liu, Z. et al. In vivo biodistribution and highly efficient tumour targeting of carbon nanotubes in mice. Nature Nanotech. 2, 47–52 (2007).

    CAS  Article  Google Scholar 

  6. 6

    Hahn, M. A., Singh, A. K., Sharma, P., Brown, S. C. & Moudgil, B. M. Nanoparticles as contrast agents for in-vivo bioimaging: current status and future perspectives. Anal. Bioanal. Chem. 399, 3–27 (2011).

    CAS  Article  Google Scholar 

  7. 7

    Smith, B. R. et al. High-resolution, serial intravital microscopic imaging of nanoparticle delivery and targeting in a small animal tumor model. Nano Today 8, 126–137 (2013).

    CAS  Article  Google Scholar 

  8. 8

    Smith, B. R. et al. Shape matters: intravital microscopy reveals surprising geometrical dependence for nanoparticles in tumor models of extravasation. Nano Lett. 12, 3369–3377 (2012).

    CAS  Article  Google Scholar 

  9. 9

    Kam, N. W., Liu, Z. & Dai, H. Carbon nanotubes as intracellular transporters for proteins and DNA: an investigation of the uptake mechanism and pathway. Angew. Chem. Int Ed. 45, 577–581 (2006).

    CAS  Article  Google Scholar 

  10. 10

    Lacerda, L. et al. Translocation mechanisms of chemically functionalised carbon nanotubes across plasma membranes. Biomaterials 33, 3334–3343 (2012).

    CAS  Article  Google Scholar 

  11. 11

    Al-Jamal, K. T. et al. Cellular uptake mechanisms of functionalised multi-walled carbon nanotubes by 3D electron tomography imaging. Nanoscale 3, 2627–2635 (2011).

    CAS  Article  Google Scholar 

  12. 12

    Moghimi, S. M. et al. Particulate systems for targeting of macrophages: basic and therapeutic concepts. J. Innate Immun. 4, 509–528 (2012).

    CAS  Article  Google Scholar 

  13. 13

    Porter, A. E. et al. Direct imaging of single-walled carbon nanotubes in cells. Nature Nanotech. 2, 713–717 (2007).

    CAS  Article  Google Scholar 

  14. 14

    Smith, B. R. et al. Real-time intravital imaging of RGD–quantum dot binding to luminal endothelium in mouse tumor neovasculature. Nano Lett. 8, 2599–2606 (2008).

    CAS  Article  Google Scholar 

  15. 15

    Smith, B. R., Cheng, Z., De, A., Rosenberg, J. & Gambhir, S. S. Dynamic visualization of RGD–quantum dot binding to tumor neovasculature and extravasation in multiple living mouse models using intravital microscopy. Small 6, 2222–2229 (2010).

    CAS  Article  Google Scholar 

  16. 16

    Leimgruber, A. et al. Behavior of endogenous tumor-associated macrophages assessed in vivo using a functionalized nanoparticle. Neoplasia 11, 459–468 (2009).

    CAS  Article  Google Scholar 

  17. 17

    Prabhakar, U. et al. Challenges and key considerations of the enhanced permeability and retention effect for nanomedicine drug delivery in oncology. Cancer Res. 73, 2412–2417 (2013).

    CAS  Article  Google Scholar 

  18. 18

    Choi, M. R. et al. A cellular trojan horse for delivery of therapeutic nanoparticles into tumors. Nano Lett. 7, 3759–3765 (2007).

    CAS  Article  Google Scholar 

  19. 19

    Owen, M. R. et al. Mathematical modeling predicts synergistic antitumor effects of combining a macrophage-based, hypoxia-targeted gene therapy with chemotherapy. Cancer Res. 71, 2826–2837 (2011).

    CAS  Article  Google Scholar 

  20. 20

    Murdoch, C., Giannoudis, A. & Lewis, C. E. Mechanisms regulating the recruitment of macrophages into hypoxic areas of tumors and other ischemic tissues. Blood 104, 2224–2234 (2004).

    CAS  Article  Google Scholar 

  21. 21

    Smith, B. R. et al. Localization to atherosclerotic plaque and biodistribution of biochemically derivatized superparamagnetic iron oxide nanoparticles (SPIONs) contrast particles for magnetic resonance imaging (MRI). Biomed. Microdev. 9, 719–727 (2007).

    Article  Google Scholar 

  22. 22

    Lacerda, L., Raffa, S., Prato, M., Bianco, A. & Kostarelos, K. Cell-penetrating CNTs for delivery of therapeutics. Nano Today 2, 38–43 (2007).

    Article  Google Scholar 

  23. 23

    Yeste, A., Nadeau, M., Burns, E. J., Weiner, H. L. & Quintana, F. J. Nanoparticle-mediated codelivery of myelin antigen and a tolerogenic small molecule suppresses experimental autoimmune encephalomyelitis. Proc. Natl Acad. Sci. USA 109, 11270–11275 (2012).

    CAS  Article  Google Scholar 

  24. 24

    Cubillos-Ruiz, J. R. et al. Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity. J. Clin. Invest. 119, 2231–2244 (2009).

    CAS  Google Scholar 

  25. 25

    Leuschner, F. et al. Therapeutic siRNA silencing in inflammatory monocytes in mice. Nature Biotechnol. 29, 1005–1010 (2011).

    CAS  Article  Google Scholar 

  26. 26

    Roy, A., Singh, M. S., Upadhyay, P. & Bhaskar, S. Combined chemo-immunotherapy as a prospective strategy to combat cancer: a nanoparticle based approach. Mol. Pharmacol. 7, 1778–88 (2010).

    CAS  Article  Google Scholar 

  27. 27

    Beatty, G. L. et al. CD40 agonists alter tumor stroma and show efficacy against pancreatic carcinoma in mice and humans. Science 331, 1612–1616 (2011).

    CAS  Article  Google Scholar 

  28. 28

    Movahedi, K. et al. Different tumor microenvironments contain functionally distinct subsets of macrophages derived from Ly6C(high) monocytes. Cancer Res. 70, 5728–5739 (2010).

    CAS  Article  Google Scholar 

  29. 29

    Gu, L. et al. Multivalent porous silicon nanoparticles enhance the immune activation potency of agonistic CD40 antibody. Adv. Mater. 24, 3981–3987 (2012).

    CAS  Article  Google Scholar 

  30. 30

    Elamanchili, P., Diwan, M., Cao, M. & Samuel, J. Characterization of poly(D,L-lactic-co-glycolic acid) based nanoparticulate system for enhanced delivery of antigens to dendritic cells. Vaccine 22, 2406–2412 (2004).

    CAS  Article  Google Scholar 

  31. 31

    Cruz, L. J. et al. Targeting nanosystems to human DCs via Fc receptor as an effective strategy to deliver antigen for immunotherapy. Mol. Pharmacol. 8, 104–116 (2011).

    CAS  Article  Google Scholar 

  32. 32

    Cruz, L. J. et al. Multimodal imaging of nanovaccine carriers targeted to human dendritic cells. Mol. Pharmacol. 8, 520–531 (2011).

    CAS  Article  Google Scholar 

  33. 33

    Gunn, J. et al. A multimodal targeting nanoparticle for selectively labeling T cells. Small 4, 712–715 (2008).

    CAS  Article  Google Scholar 

  34. 34

    Saha, P. & Geissmann, F. Toward a functional characterization of blood monocytes. Immunol. Cell Biol. 89, 2–4 (2011).

    Article  Google Scholar 

  35. 35

    Yona, S. & Jung, S. Monocytes: subsets, origins, fates and functions. Curr. Opin. Hematol. 17, 53–59 (2010).

    Article  Google Scholar 

  36. 36

    Shi, C. & Pamer, E. G. Monocyte recruitment during infection and inflammation. Nature Rev. Immunol. 11, 762–774 (2011).

    CAS  Article  Google Scholar 

  37. 37

    Primeau, A. J., Rendon, A., Hedley, D., Lilge, L. & Tannock, I. F. The distribution of the anticancer drug Doxorubicin in relation to blood vessels in solid tumors. Clin. Cancer Res. 11, 8782–8788 (2005).

    CAS  Article  Google Scholar 

  38. 38

    Ingersoll, M. A. et al. Comparison of gene expression profiles between human and mouse monocyte subsets. Blood 115, e10–e19 (2010).

    CAS  Article  Google Scholar 

  39. 39

    De Nicola, M. et al. Effects of carbon nanotubes on human monocytes. Ann. NY Acad. Sci. 1171, 600–605 (2009).

    CAS  Article  Google Scholar 

  40. 40

    Schipper, M. L. et al. A pilot toxicology study of single-walled carbon nanotubes in a small sample of mice. Nature Nanotech. 3, 216–221 (2008).

    CAS  Article  Google Scholar 

  41. 41

    Lee, H. J. et al. Amine-modified single-walled carbon nanotubes protect neurons from injury in a rat stroke model. Nature Nanotech. 6, 121–125 (2011).

    CAS  Article  Google Scholar 

  42. 42

    Liu, Z., Tabakman, S. M., Chen, Z. & Dai, H. Preparation of carbon nanotube bioconjugates for biomedical applications. Nature Protoc. 4, 1372–1382 (2009).

    CAS  Article  Google Scholar 

  43. 43

    Herzenberg, L. A., Tung, J., Moore, W. A. & Parks, D. R. Interpreting flow cytometry data: a guide for the perplexed. Nature Immunol. 7, 681–685 (2006).

    CAS  Article  Google Scholar 

  44. 44

    Ghosn, E. E. et al. Two physically, functionally, and developmentally distinct peritoneal macrophage subsets. Proc. Natl Acad. Sci. USA 107, 2568–2573 (2010).

    CAS  Article  Google Scholar 

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This work was supported by a number of grants. B.R.S. was supported by a National Institutes of Health (NIH) 25T post-doctoral training grant and is currently supported by a K99/R00 award (K99 CA160764). S.S.G. was supported by a Center for Cancer Nanotechnology Excellence–Translation (CCNE-T)-grant (National Cancer Institute U54 CA119367) and in vivo cellular and molecular imaging (ICMIC) grant (P50 CA114747). The authors thank C. Ball for discussions related to this work. The authors acknowledge technical assistance in experiments and analysis from M. Philips, S. Tabakman, J. Rosenberg, S. Kusy, C. Nielsen, H. Dai, A-L. Koh, R. Sinclair, C. Zavaleta, J. Strommer and CytoViva.

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B.R.S. and S.S.G. conceived and designed the experiments. B.R.S. performed the experiments and contributed materials and analysis tools. B.R.S. and S.S.G. analysed the data and wrote the manuscript. E.E.B.G. designed, performed and analysed 12-colour, 14-parameter FACS for immune cell analysis of blood samples, discussed results, contributed reagents, and commented on the manuscript. L.A.H. provided guidance and assisted with analysis regarding high-dimensional flow cytometry and contributed materials and analysis tools. H.R. assisted with analyses of intravital imaging experiments. B.R.S. and J.A.P. designed, performed and analysed initial flow cytometry assays. T.L. assisted with characterization of nanotubes.

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Correspondence to Bryan Ronain Smith or Sanjiv Sam Gambhir.

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The authors declare no competing financial interests.

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Smith, B., Ghosn, E., Rallapalli, H. et al. Selective uptake of single-walled carbon nanotubes by circulating monocytes for enhanced tumour delivery. Nature Nanotech 9, 481–487 (2014).

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