SVN MED TECHNOLOGY

The normal components of blood are red blood cells (RBCs), leukocytes (white blood cells, or WBCs) and platelets. CTCs are abnormal blood cells shed from tumors that circulate through the bloodstream until they are either destroyed or take root in tissue, where they form a new tumor (a metastasis or “met”). Without CTCs, metastasis is impossible.

Size and Shape Matters

One important characteristic of blood cells is their deformability: the ability to change shape in order to traverse through the narrow capillaries which separate arterial blood (blood pumped out by the heart) from venous blood (blood returning to the heart after passing through a capillary). RBCs are known to be highly deformable, effectively and very quickly changing shape from a donut to a sausage as they pass through capillaries. Platelets and WBCs are less deformable than RBCs; but they nevertheless must and do traverse through capillaries, albeit at a slower rate. CTCs are the most rigid (least deformable) type of blood cell by several orders of magnitude. It is this characteristic, in addition to size differences, that SVN MED’s technology is uniquely capable of exploiting. SVN MED’s filter allows cells that can easily deform – as all healthy blood cells can – to pass through unharmed, while trapping CTCs, which are too rigid to change their shape enough to pass through the filter.

​The following table shows the typical number and sizes of blood cells in typical humans:

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CROSS-FLOW FILTER

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1. Our cross-flow filtration technology exploits the differential size and flexibility of CTCs and normal blood components. Small but numerous cells—RBCs (2 x 8 microns) and platelets (2 microns in diameter)—are separated using a filter with small pores. The largest component in normal blood—WBCs—are typically 10-15 microns in diameter; while CTCs are typically 15-20 microns in diameter, and much less deformable. These cells are retained for further processing and analysis or removed and discarded (in the case of the therapeutic application).

FILTER DESIGN

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2. Our filter is comprised of a micro-machined polymer that allows the passage of tens of millions of RBCs, platelets and WBCs per second, while blocking CTCs. Design algorithms balance blood flow across and through the filter, while maintaining low trans-membrane pressure and preventing damage to the healthy components of the blood.