Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Cancer-derived exosomes loaded with ultrathin palladium nanosheets for targeted bioorthogonal catalysis


The transformational impact of bioorthogonal chemistries has inspired new strategies for the in vivo synthesis of bioactive agents through non-natural means. Among these, Pd catalysts have played a prominent role in the growing subfield of bioorthogonal catalysis by producing xenobiotics and uncaging biomolecules in living systems. However, delivering catalysts selectively to specific cell types still lags behind catalyst development. Here, we have developed a bioartificial device comprising cancer-derived exosomes that are loaded with Pd catalysts by a method that enables the controlled assembly of Pd nanosheets directly inside the vesicles. This hybrid system mediates Pd-triggered dealkylation reactions in vitro and inside cells, and displays preferential tropism for their progenitor cells. The use of Trojan exosomes to deliver abiotic catalysts into designated cancer cells creates the opportunity for a new targeted therapy modality; that is, exosome-directed catalyst prodrug therapy, whose first steps are presented herein with the cell-specific release of the anticancer drug panobinostat.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Preparation and characterization of Pd-functionalized exosomes.
Fig. 2: A study of the catalytic properties of Pd-ExoA549.
Fig. 3: A confocal study of Pd-ExoA549 internalization in A549 cells.
Fig. 4: The design and synthesis of prodrug 4 and targeted intracellular activation mediated by Pd-ExoA549 and Pd-ExoU87 in A549 and U87 cells.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.


  1. 1.

    Streu, C. & Meggers, E. Ruthenium-induced allylcarbamate cleavage in living cells. Angew. Chem. Int. Ed. 45, 5645–5648 (2006).

    CAS  Article  Google Scholar 

  2. 2.

    Li, N., Lim, R. K., Edwardraja, S. & Lin, Q. Copper-free sonogashira cross-coupling for functionalization of alkyne-encoded proteins in aqueous medium and in bacterial cells. J. Am. Chem. Soc. 133, 15316–15319 (2011).

    CAS  Article  Google Scholar 

  3. 3.

    Spicer, C. D., Triemer, T. & Davis, B. G. Palladium-mediated cell-surface labeling. J. Am. Chem. Soc. 134, 800–803 (2012).

    CAS  Article  Google Scholar 

  4. 4.

    Michel, B. W., Lippert, A. R. & Chang, C. J. A reaction-based fluorescent probe for selective imaging of carbon monoxide in living cells using a palladium-mediated carbonylation. J. Am. Chem. Soc. 134, 15668–15671 (2012).

    CAS  Article  Google Scholar 

  5. 5.

    Yang, M., Jia, S., Zhang, X. & Chen, P. Palladium-triggered deprotection chemistry for protein activation in living cells. Nat. Chem. 6, 352–361 (2014).

    Article  Google Scholar 

  6. 6.

    Mascareñas, J. L., Sánchez, M. I., Penas, C. & Vázquez, M. E. Metal-catalyzed uncaging of DNA-binding agents in living cells. Chem. Sci. 5, 1901 (2014).

    Article  Google Scholar 

  7. 7.

    Völker, T., Dempwolff, F., Graumann, P. L. & Meggers, E. Angew. Chem. Int. Ed. 53, 10536 (2014).

    Article  Google Scholar 

  8. 8.

    Wang, J. et al. Chemical remodeling of cell-surface sialic acids through a palladium-triggered bioorthogonal elimination reaction. Angew. Chem. Int. Ed. 54, 5364–5368 (2015).

    CAS  Article  Google Scholar 

  9. 9.

    Tomás-Gamasa, M., Martínez-Calvo, M., Couceiro, J. R. & Mascareñas, J. L. Transition metal catalysis in the mitochondria of living cells. Nat. Commun. 7, 12538 (2016).

    Article  Google Scholar 

  10. 10.

    Tsubokura, K. et al. In vivo gold complex catalysis within live mice. Angew. Chem. Int. Ed. 56, 3579–3584 (2017).

    CAS  Article  Google Scholar 

  11. 11.

    Destito, P., Couceiro, J. R., Faustino, H., López, F. & Mascareñas, J. L. Ruthenium‐catalyzed azide-thioalkyne cycloadditions in aqueous media: a mild, orthogonal, and biocompatible chemical ligation. Angew. Chem. Int. Ed. 56, 10766–10770 (2017).

    CAS  Article  Google Scholar 

  12. 12.

    Vidal, C., Tomás-Gamasa, M., Destito, P., López, F. & Mascareñas, J. L. Concurrent and orthogonal gold(i) and ruthenium(ii) catalysis inside living cells. Nat. Commun. 9, 1913 (2018).

    Article  Google Scholar 

  13. 13.

    Stenton, B. J., Oliveira, B. L., Matos, M. J., Sinatra, L. & Bernardes, G. J. L. A thioether-directed palladium-cleavable linker for targeted bioorthogonal drug decaging. Chem. Sci. 9, 4185–4189 (2018).

    CAS  Article  Google Scholar 

  14. 14.

    Chatterjee, A. et al. An enantioselective artificial Suzukiase based on the biotin–streptavidin technology. Chem. Sci. 7, 673–677 (2016).

    CAS  Article  Google Scholar 

  15. 15.

    Jeschek, M. et al. Directed evolution of artificial metalloenzymes for in vivo metathesis. Nature 537, 661–665 (2016).

    CAS  Article  Google Scholar 

  16. 16.

    Okamoto, Y. et al. A cell-penetrating artificial metalloenzyme regulates a gene switch in a designer mammalian cell. Nat. Commun. 9, 1943 (2018).

    Article  Google Scholar 

  17. 17.

    Yusop, R. M., Unciti-Broceta, A., Johansson, E. M. V., Sánchez-Martín, R. M. & Bradley, M. Palladium-mediated intracellular chemistry. Nat. Chem. 3, 239–243 (2011).

    CAS  Article  Google Scholar 

  18. 18.

    Unciti-Broceta, A., Johansson, E. M. V., Yusop, R. M., Sánchez-Martín, R. M. & Bradley, M. Synthesis of polystyrene microspheres and functionalization with Pd(0) nanoparticles to perform bioorthogonal organometallic chemistry in living cells. Nat. Protoc. 7, 1207–1218 (2012).

    CAS  Article  Google Scholar 

  19. 19.

    Tonga, G. Y. et al. Supramolecular regulation of bioorthogonal catalysis in cells using nanoparticle-embedded transition metal catalysts. Nat. Chem. 7, 597–603 (2015).

    CAS  Article  Google Scholar 

  20. 20.

    Miller, M. A. et al. Nano-palladium is a cellular catalyst for in vivo chemistry. Nat. Commun. 8, 15906–15919 (2017).

    CAS  Article  Google Scholar 

  21. 21.

    Clavadetscher, J., Indrigo, E., Chankeshwara, S. V., Lilienkampf, A. & Bradley, M. In-cell dual drug synthesis by cancer-targeting palladium catalysts. Angew. Chem. Int. Ed. 56, 6864–6868 (2017).

    CAS  Article  Google Scholar 

  22. 22.

    Hoop, M. et al. Mobile magnetic nanocatalysts for bioorthogonal targeted cancer therapy. Adv. Funct. Mater. 28, 1705920 (2018).

    Article  Google Scholar 

  23. 23.

    Liu, Y. et al. Catalytically active single-chain polymeric nanoparticles: exploring their functions in complex biological media. J. Am. Chem. Soc. 140, 3423–3433 (2018).

    CAS  Article  Google Scholar 

  24. 24.

    Wang, F., Zhang, Y., Du, Z., Ren, J. & Qu, X. Designed heterogeneous palladium catalysts for reversible light-controlled bioorthogonal catalysis in living cells. Nat. Commun. 9, 1209 (2018).

    Article  Google Scholar 

  25. 25.

    Weiss, J. T. et al. Extracellular palladium-catalysed dealkylation of 5-fluoro-1-propargyl-uracil as a bioorthogonally activated prodrug approach. Nat. Commun. 5, 3277 (2014).

    Article  Google Scholar 

  26. 26.

    Weiss, J. T. et al. Development and bioorthogonal activation of palladium-labile prodrugs of gemcitabine. J. Med. Chem. 57, 5395–5404 (2014).

    CAS  Article  Google Scholar 

  27. 27.

    Weiss, J. T., Carragher, N. O. & Unciti-Broceta, A. Palladium-mediated dealkylation of N-propargyl-floxuridine as a bioorthogonal oxygen-independent prodrug strategy. Sci. Rep. 5, 9329 (2015).

    CAS  Article  Google Scholar 

  28. 28.

    Clavadetscher, J. et al. Copper catalysis in living systems and in situ drug synthesis. Angew. Chem. Int. Ed. 55, 15662–15666 (2016).

    CAS  Article  Google Scholar 

  29. 29.

    Pérez-López, A. M. et al. Gold-triggered uncaging chemistry in living systems. Angew. Chem. Int. Ed. 56, 12548–12552 (2017).

    Article  Google Scholar 

  30. 30.

    Bray, T. L. et al. Bright insights into palladium-triggered local chemotherapy. Chem. Sci. 9, 7354–7361 (2018).

    CAS  Article  Google Scholar 

  31. 31.

    Adam, C. et al. Bioorthogonal uncaging of the active metabolite of irinotecan by palladium‐functionalized microdevices. Chem. Eur. J. 24, 16783–16790 (2018).

    CAS  Article  Google Scholar 

  32. 32.

    Eda, S. et al. Biocompatibility and therapeutic potential of glycosylated albumin artificial metalloenzymes. Nat. Catal. (2019).

  33. 33.

    Valadi, H. et al. Exosome mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat. Cell Biol. 9, 654–659 (2007).

    CAS  Article  Google Scholar 

  34. 34.

    Gould, S. J., Booth, A. M. & Hildreth, J. E. The Trojan exosome hypothesis. Proc. Natl Acad. Sci. USA 100, 10592–10597 (2003).

    CAS  Article  Google Scholar 

  35. 35.

    Gourlay, J. et al. The emergent role of exosomes in glioma. J. Clin. Neurosci. 35, 13–23 (2017).

    CAS  Article  Google Scholar 

  36. 36.

    Hornick, N. I. et al. AML suppresses hematopoiesis by releasing exosomes that contain microRNAs targeting c-MYB. Sci. Signal. 9, ra88 (2016).

    Article  Google Scholar 

  37. 37.

    Huan, J. et al. Coordinate regulation of residual bone marrow function by paracrine trafficking of AML exosomes. Leukemia 29, 2285–2295 (2015).

    CAS  Article  Google Scholar 

  38. 38.

    Alvarez-Erviti, L. et al. Delivery of siRNA to the mouse brain by systemic injection of targeted exosomes. Nat. Biotechnol. 29, 341–345 (2011).

    CAS  Article  Google Scholar 

  39. 39.

    Li, X. et al. Exosomes in cancer: small transporters with big functions. Cancer Lett. 435, 55–65 (2018).

    CAS  Article  Google Scholar 

  40. 40.

    Meckes, D. G. Jr Exosomal communication goes viral. J. Virol. 89, 5200–5203 (2015).

    CAS  Article  Google Scholar 

  41. 41.

    Abrami, L. et al. Hijacking multivesicular bodies enables long-term and exosome-mediated long-distance action of anthrax toxin. Cell Rep. 5, 986–996 (2013).

    CAS  Article  Google Scholar 

  42. 42.

    Cross, R. Meet the exosome, the rising star in drug delivery. Chem. Eng. News 96, 22–23 (2018).

    Google Scholar 

  43. 43.

    Zitvogel, L. et al. Eradication of established murine tumors using a novel cell-free vaccine: dendritic cell-derived exosomes. Nat. Med. 4, 594–600 (1998).

    CAS  Article  Google Scholar 

  44. 44.

    Munoz, J. L. et al. Delivery of functional anti-miR-9 by mesenchymal stem cell-derived exosomes to glioblastoma multiforme cells conferred chemosensitivity. Mol. Ther. Nucleic Acids 2, e126 (2013).

    Article  Google Scholar 

  45. 45.

    Smyth, T. et al. Surface functionalization of exosomes using click chemistry. Bioconjug. Chem. 25, 1777–1784 (2014).

    CAS  Article  Google Scholar 

  46. 46.

    Yang, T. et al. Exosome delivered anticancer drugs across the blood-brain barrier for brain cancer therapy in Danio rerio. Pharm. Res. 32, 2003–2014 (2015).

    CAS  Article  Google Scholar 

  47. 47.

    Kamerkar, S. et al. Exosomes facilitate therapeutic targeting of oncogenic KRAS in pancreatic cancer. Nature 546, 498–503 (2017).

    CAS  Article  Google Scholar 

  48. 48.

    György, B. et al. Rescue of hearing by gene delivery to inner-ear hair cells using exosome-associated AAV. Mol. Ther. 25, 379–391 (2017).

    Article  Google Scholar 

  49. 49.

    Kim, S. M. et al. Cancer-derived exosomes as a delivery platform of CRISPR/Cas9 confer cancer cell tropism-dependent targeting. J. Control. Release 266, 8–16 (2017).

    CAS  Article  Google Scholar 

  50. 50.

    Wang, Q. et al. ARMMs as a versatile platform for intracellular delivery of macromolecules. Nat. Commun. 9, 960 (2018).

    Article  Google Scholar 

  51. 51.

    Hood, J. L., Scott, M. J. & Wickline, S. A. Maximizing exosomes colloidal stability following electroporation. Anal. Biochem. 448, 41–49 (2014).

    CAS  Article  Google Scholar 

  52. 52.

    Alhasan, A. H., Patel, P. C., Choi, C. H. J. & Mirkin, C. A. Exosome encased spherical nucleic acid gold nanoparticle conjugates as potential microRNA regulation agents. Small 10, 186–192 (2014).

    CAS  Article  Google Scholar 

  53. 53.

    Busato, A. et al. Magnetic resonance imaging of ultrasmall superparamagnetic iron oxide-labeled exosomes from stem cells: a new method to obtain labeled exosomes. Int. J. Nanomed. 11, 2481–2490 (2016).

    CAS  Google Scholar 

  54. 54.

    Illes, B. et al. Exosome-coated metal–organic framework nanoparticles: an efficient drug delivery platform. Chem. Mater. 29, 8042–8046 (2017).

    CAS  Article  Google Scholar 

  55. 55.

    Betzer, O. et al. In vivo neuroimaging of exosomes using gold nanoparticles. ACS Nano 11, 10883–10893 (2017).

    CAS  Article  Google Scholar 

  56. 56.

    Ha, D., Yang, N. & Nadithe, V. Exosomes as therapeutic drug carriers and delivery vehicles across biological membranes: current perspectives and future challenges. Acta Pharm. Sin. B. 6, 287–296 (2016).

    Article  Google Scholar 

  57. 57.

    Luan, X. et al. Engineering exosomes as refined biological nanoplatforms for drug delivery. Acta Pharmacol. Sin. 38, 754–763 (2017).

    CAS  Article  Google Scholar 

  58. 58.

    Sebastian, V., Smith, C. D. & Jensen, K. F. Shape-controlled continuous synthesis of metal nanostructures. Nanoscale 8, 7534–7543 (2016).

    CAS  Article  Google Scholar 

  59. 59.

    Herrer, L. et al. High surface coverage of a self-assembled monolayer by in situ synthesis of palladium nanodeposits. Nanoscale 9, 13281–13290 (2017).

    CAS  Article  Google Scholar 

  60. 60.

    Zhang, D. et al. An in situ TEM study of the surface oxidation of palladium nanocrystals assisted by electron irradiation. Nanoscale 9, 6327–6333 (2017).

    CAS  Article  Google Scholar 

  61. 61.

    Kikot, P., Polat, A., Achilli, E., Fernandez Lahore, M. & Grasselli, M. Immobilized palladium(ii) ion affinity chromatography for recovery of recombinant proteins with peptide tags containing histidine and cysteine. J. Mol. Recognit. 27, 659–668 (2014).

    CAS  Article  Google Scholar 

  62. 62.

    Raedler, L. A. Farydak (panobinostat): first HDAC inhibitor approved for patients with relapsed multiple myeloma. Am. Health Drug Benefits 9, 84–87 (2016).

    PubMed  PubMed Central  Google Scholar 

  63. 63.

    Zheng, S. et al. Biocompatible boron-containing prodrugs of belinostat for the potential treatment of solid tumors. ACS Med. Chem. Lett. 9, 149–154 (2018).

    CAS  Article  Google Scholar 

  64. 64.

    Rubio-Ruiz, B., Weiss, J. T. & Unciti-Broceta, A. Efficient palladium-triggered release of vorinostat from a bioorthogonal precursor. J. Med. Chem. 59, 9974–9980 (2016).

    CAS  Article  Google Scholar 

  65. 65.

    Wang, H. et al. Discovery of (2E)-3-{2-butyl-1-[2-(diethylamino)ethyl]-1H-benzimidazol-5-yl}-N-hydroxyacrylamide (SB939), an orally active histone deacetylase inhibitor with a superior preclinical profile. J. Med. Chem. 54, 4694–4720 (2011).

    CAS  Article  Google Scholar 

  66. 66.

    Sancho-Albero, M. et al. Exosome origin determines cell targeting and the transfer of therapeutic nanoparticles towards target cells. J. Nanobiotechnol. 17, 16 (2019).

    Article  Google Scholar 

  67. 67.

    Sletten, E. M. & Bertozzi, C. R. Bioorthogonal chemistry: fishing for selectivity in a sea of functionality. Angew. Chem. Int. Ed. 48, 6974–6998 (2009).

    CAS  Article  Google Scholar 

  68. 68.

    Li, J. & Chen, P. R. Development and application of bond cleavage reactions in bioorthogonal chemistry. Nat. Chem. Biol. 12, 129–137 (2016).

    CAS  Article  Google Scholar 

  69. 69.

    Devaraj, N. K. The future of bioorthogonal chemistry. ACS Cent. Sci. 4, 952–959 (2018).

    CAS  Article  Google Scholar 

  70. 70.

    Capes-Davis, A. et al. Check your cultures! A list of cross-contaminated or misidentified cell lines. Int. J. Cancer 127, 1–8 (2010).

    CAS  Article  Google Scholar 

Download references


We gratefully acknowledge financial support from EPSRC (Healthcare Technology Challenge award no. EP/N021134/1) and the ERC Advanced Grant CADENCE (grant no. ERC-2016-ADG-742684). We also thank S. Irusta at the University of Zaragoza for performing X-ray photoelectron spectroscopy measurements. M.S.-A. thanks the Spanish government for an FPU PhD research fellowship. B.R.-R. thanks the EC (grant no. H2020-MSCA-IF-2014–658833). M.A. thanks the financial support of the ERC Consolidator Grant programme (grant no. ERC-2013-CoG-614715). P.M.-D. thanks AECC Fund and Refbio-Lactodermal for financial support.

Author information




M.S.-A., B.R.-R., A.M.P.-L. and V.S. prepared and characterised the materials, planned and performed the experiments, analysed the data and wrote the Methods; V.S., P.M.-D. and M.A. planned and supervised the research, analysed the data and contributed to the manuscript writing; J.S. and A.U.-B. designed, coordinated and supervised the research, analysed the data and wrote the paper. All the authors checked the manuscript.

Corresponding authors

Correspondence to Jesús Santamaría or Asier Unciti-Broceta.

Ethics declarations

Competing interests

The authors declare that compound 4 is protected under patent application WO/2017/199028.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Reporting Summary

Supplementary Video 1

Real-time imaging of Pd-ExoA549-mediated conversion of pro-fluorophore 1 into red fluorescent fluorophore 2. The reactions were performed in PBS at room temperature and imaged by time-lapse microscopy with a ×20 objective (Ex/Em: 560/630 nm, Leica AF6000 LX) for 24 h. The frames were taken every 15 min in differential interference contrast mode (top) and under fluorescence emission (bottom). Left (positive control): resorufin 2 alone (20 μM). Middle (negative control): probe 1 alone (20 μM). Right (activation experiment): probe 1 (20 μM) + Pd-ExoA549 (0.5 μg ml).

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sancho-Albero, M., Rubio-Ruiz, B., Pérez-López, A.M. et al. Cancer-derived exosomes loaded with ultrathin palladium nanosheets for targeted bioorthogonal catalysis. Nat Catal 2, 864–872 (2019).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing