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.

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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.


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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.

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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.

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Correspondence to Jesús Santamaría or Asier Unciti-Broceta.

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

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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).

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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).

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