TABLE II.

Summary of commercially available systems.

CTC commercial system	Principle	Reference
CellSearch	The CellSearch system (Veridex, Raritan, NJ, USA) is the only US FDA-approved CTC enumeration system.132 Utilizing ferrofluid nanoparticles with antibodies that target epithelial cell adhesion, CTCs are magnetically separated from the bulk of other cells in the blood. This system could successfully enumerate breast, prostate, and colorectal cancers through immunomagnetic technology. Disadvantages are high cost and low efficiency.	132
IsoFlux	The IsoFlux System (Fluxion Biosciences Inc., South San Francisco, CA) could provide high-sensitivity rare cell isolation coupled with a novel cell retrieval mechanism.133 The system employs immunomagnetic beads that facilitate use of single or multiple capture antibodies to target cells of a specific pathology. With an externally applied magnetic field the sample flow over a microfluidic device that contains an isolation zone to capture CTCs on the upper surface of the cartridge. The roof of the microfluidic channel could detach from the rest of the cartridge and transfers off-chip with the CTCs remained on its surface, providing near perfect transfer efficiency. It is possible for the IsoFlex System to molecular characterize intact viable CTCs or isolated DNA, RNA, or protein.	133
ImageStream	The ImageStream (Amnis, Seattle, WA, USA) is an imaging cytometry device that combines the strengths of flow cytometry and fluorescent microscopy in a single platform and has potential in applications to CTC counting.134 ImageStream platform for CTC enumeration potentially has a value for the early diagnosis of disseminated disease. Disadvantage is precision needed for the enumeration of low number of CTC.	134
Clearbridge BioMedics' ClearCell FX System	The ClearCell FX1 System works as a leading, automated, label-free liquid biopsy device for the enrichment of target cells from blood.79 The system employs the innovative microfluidic CTChip to isolate and retrieve intact, viable target cells from a patient's blood sample. This is a spiral microfluidic chip that could size-based separate and retrieve CTCs from blood with high throughput using the Dean drag force coupled with inertial microfluidics phenomenon.	79
Celsee Diagnostics CTC system	Key component of this system is a microfluidic chip with individual compartment in the shape of a bowl as the cross section and with a 7.5 μm width tunnel located below as filter.135 Blood sample was injected from top and enriched in the bowl and hematological cells and waste flow away from the bottom. It is based on size and deformability. The Celsee PREP 400™ system (Celsee Diagnostics, Plymouth, MI) is an automated system of this microfluidic device and contains a parallel network of four microfluidic chips each of which has approximately 56 320 capture chambers. The downstream of identification of individual CTCs can use a wide array of antibodies and DNA/RNA-based probes.	135
Parsortix cell separation system from ANGLE plc Company	Parsortix™ Cell Separation System (ANGLE North America, Inc., King of Prussia, PA) is a microfluidic based technology capturing CTCs based on size and deformability.136 It has reproducibly high capture efficiency and obtains highly enriched, viable (viability dependent on preservative used) CTCs that are amenable to a multitude of downstream analysis even for single cells. There exists a Parsortix GEN3 Cell Separation Cassette showing how the blood flows into the cassette, over the step structures and through the critical gap. The separation cassette is with a 6.5 μm critical gap size.	136