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The entry of nanoparticles into solid tumours


The concept of nanoparticle transport through gaps between endothelial cells (inter-endothelial gaps) in the tumour blood vessel is a central paradigm in cancer nanomedicine. The size of these gaps was found to be up to 2,000 nm. This justified the development of nanoparticles to treat solid tumours as their size is small enough to extravasate and access the tumour microenvironment. Here we show that these inter-endothelial gaps are not responsible for the transport of nanoparticles into solid tumours. Instead, we found that up to 97% of nanoparticles enter tumours using an active process through endothelial cells. This result is derived from analysis of four different mouse models, three different types of human tumours, mathematical simulation and modelling, and two different types of imaging techniques. These results challenge our current rationale for developing cancer nanomedicine and suggest that understanding these active pathways will unlock strategies to enhance tumour accumulation.

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Fig. 1: Tumour vasculature is mostly continuous and gaps occur at a very low frequency.
Fig. 2: Nanoparticles can extravasate through active trans-endothelial pathways.
Fig. 3: Zombie model preserves the architecture of vessels inside the animal.
Fig. 4: The dominant mechanism of nanoparticle entry into solid tumours is trans-endothelial.
Fig. 5: Nanoparticles correlate significantly with trans-endothelial pathways of transport.
Fig. 6: Tumour vessels in cancer patients are continuous with similar structural features to those of mouse models.

Data availability

All the annotated and analysed TEM images are uploaded on the Figshare server. This includes an Excel sheet that summarizes the results and overall analysis of the TEM images. This is available at 3D images used in the simulations are also stored on Figshare and will be automatically downloaded by the code used for simulations. All other datasets generated and analysed during this study are available from the corresponding author upon reasonable request.

Code availability

All code for simulations of nanoparticles in tumours can be found at

The code for spatial analysis of nanoparticles is uploaded to Figshare at


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The authors thank D. Holmyard and A. Darbandi at SickKids Hospital (Toronto) for their help in preparing tissue grids for TEM. The authors also thank the Ontario Tumour Bank (Canada) for cooperation with the sample collection from human biopsy samples. The Canadian authors also thank the Canadian Research Chairs Program (950-223924), Canadian Cancer Society (502200 and 706286), Natural Sciences and Engineering Research Council (2015-06397 and graduate fellowships), Walter C. Sumner Memorial Fellowship (graduate fellowships), and Canadian Institute of Health Research (PJT-148848 and FDN-159932, and graduate fellowships) for funding support. M.E. thanks the Department of Defence (DoD) for grant W81XWH-14-1-0078 and is a BCRP-Era of Hope Scholar. L.M. thanks Northwell Health for funding.

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Authors and Affiliations



S.S., A.M.S. and W.C.W.C. conceived the idea, S.S., A.M.S., J.N., B.R.K., L.M., J.L.Y.W., S.W., B.O. and Z.L. performed the experiments. S.S., A.M.S., J.N., B.R.K., P.M., Y.Z., N.U.R. and T.H. annotated the TEM images. A.M.S., J.R. and A.Z. performed the computational simulations and analysis. S.G., A.S. and L.W. provided the PDX model. L.M. and M.E. provided the GEMM model. S.S., A.M.S., J.N., B.R.K., M.E. and W.C.W.C. prepared and revised the manuscript.

Corresponding author

Correspondence to Warren C. W. Chan.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–10, Tables 1–13, Notes 1 and 2, Discussion and References.

Reporting Summary

Supplementary Video 1

The video recording of the fixation and nanoparticle circulation procedure for Zombie model has been attached. Mouse was fixed via transcardial perfusion. Known volume and concentration of nanoparticles were added into the perfusion chamber and the nanoparticles were perfused throughout the fixed mouse with a peristaltic pump.

Supplementary Video 2a

Time lapse videos from intravital imaging of 4T1 tumour model showing that nanoparticles form “hotspots” along the vessels. These sites of extravasation are colocalizing with the vessels. These hotspots are heterogenous in their distribution across the field of view.

Supplementary Video 2b

Time lapse videos from intravital imaging of MMTV-PyMT tumour model showing that nanoparticles form “hotspots” along the vessels similar to 4T1 model in Video S2a.

Supplementary Video 3a

Video rendering of 3D images of human breast tumour immunolabeled for V-Cadherin and PV-1.

Supplementary Video 3b

Video rendering of 3D images of human ovarian tumour immunolabeled for V-Cadherin and PV-1.

Supplementary Video 3c

Video rendering of 3D images of human brain tumour immunolabeled for V-Cadherin and PV-1.

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Sindhwani, S., Syed, A.M., Ngai, J. et al. The entry of nanoparticles into solid tumours. Nat. Mater. 19, 566–575 (2020).

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