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Tracking metastasis tumor cell extravasation with quantum dot nanocrystals and fluorescence emission-scanning microscopy


Central Question : Can metastasis and extravasation be traced in-vivo with the use of quantum dot nanocrystals without causing toxicity upon prolonged exposure to quantum dots?

Presented by

(1) Bianca Reichart
(2) Gayathri Janarthanam


Introduction :


Metastasis:

> Pathogenic agent's spread from an initial site to a different site within the host's body.


> Lymphatic or hematogenous spread:
circulating tumor cells acquire the ability to penetrate the walls of lymphatic or blood vessels.


> Typical for a malignant tumor.


Extravasation




Cascade of events:


> Tumor cell arrest on the endothelium


> Formation of dynamic contacts


> Significant cytoskeletal changes


> Tumor cell transendothelial migration


> Invasion into the surrounding matrix





Labeling tumor cells with QD


> QD was packed in cationic lipids.

> Can efficiently transduce negatively charged nucleic acids into the cytoplasm.


Intracellular labeling of tumor cells by QDs permits

in vivo imaging despite tissue autofluorescence.

Fluorescence emission spectroscopy:





> Scans the surface of a sample with an electron beam.


> High-resolution images.




IN-VIVO IMAGING :


> QDs - good multiphoton absorption between 700 - 1000 nm.

> QDs labeled with orange cell trackers were injected into the mice.

> QDs -circles; orange trackers - diamonds; lectin - squares => distinguishable from tissue autofluorescence.


> QDs - Cadmium and selenium cores.


> May cause toxicity upon prolonged stay in vivo.


> If QDs aid in extravasation/ affected the survival of the tumor cells:

Qd-labeled tumor cells in tissues < QD-labelled cells during injection.


> QD - labeled tumor cells were quantified after 40 days - no significant difference; Did not interfere with the growth of the tumor cells or cause extravasation.


> Comparison for 5 days vs 40 days - no unlabelled cells found; remained the same relatively in both cases - proof that QDs have no role in extravasation.


> Black bars: in-vitro

Grey bars: in-vivo




Multiphoton imaging of the QDs :


> Thicker tissues - absorb and scatter visible light => infrared excitation is suitable in vivo.

> Different colour emitting QDs ranging 510, 550, 570, 590, and 610 nm were identified using multiphoton emission-scanning microscopy.

> Helps identify multiple populations of cells.






> Image A: Different QDs excited at 820 nm after 5 h of injection.

> Image B: Circles - 510 nm QDs ; Diamonds -570 nm QDs;

> Image C: QDs under a coverslip excited at 680 nm.


List of sources:


Voura, E. B., Jaiswal, J. K., Mattoussi, H., & Simon, S. M. (2004). Tracking metastatic tumor cell extravasation with quantum

dot nanocrystals and fluorescence emission-scanning microscopy. Nature Medicine, 10(9), 993–998.

https://doi.org/10.1038/nm1096


Peng, F., Setyawati, M. I., Tee, J. K., Ding, X., Wang, J., Nga, M. E., Ho, H. K., & Leong, D. T. (2019). Nanoparticles promote

in vivo breast cancer cell intravasation and extravasation by inducing endothelial leakiness. Nature Nanotechnology, 14(3),

279–286. https://doi.org/10.1038/s41565-018-0356-z


Chen, M. B., Whisler, J. A., Jeon, J. S., & Kamm, R. D. (2013). Mechanisms of tumor cell extravasation in an in vitro

microvascular network platform. Integrative Biology : Quantitative Biosciences from Nano to Macro, 5(10), 1262.

https://doi.org/10.1039/C3IB40149A


https://www.edn.com/quantum-dots-explained/


https://en.wikipedia.org/wiki/Metastasis


https://www.cancer.net/navigating-cancer-care/cancer-basics/what-metastasis


Cho, Hye Jin et al. “Multiphoton microscopy: an introduction to gastroenterologists.” World journal of gastroenterology vol. 17,40 (2011): 4456-60. doi:10.3748/wjg.v17.i40.4456


https://www.microscopyu.com/techniques/multi-photon/multiphoton-microscopy

https://en.wikipedia.org/wiki/Cadmium_selenide