Table 2.

(A): Outlining circulating tumor cells (CTCs) enrichment techniques based on various mechanisms (Cell biophysical-based techniques). (B) Outlining circulating tumor cells (CTCs) enrichment techniques based on various mechanisms (Immunoaffinity-based techniques).

(A)
Category	Typical Platform	Description	Capture Efficiency	Advantages	Disadvantages	References
Size-based	ISET®	Filtration device	87%	Recovery of a heterogeneous population of CTCs, high purity, rapid, simple process	Sample loss during mononuclear cell depletion	[85]
	ScreenCell	Microfiltration device (pores of defined size for CTC capture)	74–91%	Recovery of a heterogeneous population of CTCs, high throughput, cheap and easy to produce, rapid process	Limited to larger CTCs, require additional enrichment step	[86]
	Vortex VTX-1	Inertial microfluidic chip (size-based separation)	53.8–71.6%	Recovery of a heterogeneous population of CTCs, fully automated process, high throughput (7.5 mL/20 min)	Limited to larger CTCs may require additional specific staining for cell identification.	[87]
Density	Ficoll-Hypaque	Blood is layered over a Ficoll-Hypaque	>90%	Simple and inexpensive	Low throughput (0.01−1.0 mL/h), high WBC contamination, loss of CTCs	[83,88]
	OncoQuick	Porous membrane filtration followed by density-grade centrifugation	84%	Simple and inexpensive	Loss of CTC, low purity	[88]
Bioelectrical properties	APOCELL	Dielectrophoresis field flow fractionation (size-based separation)	75%	Recovery of a heterogeneous population of CTCs, high throughput (7.5–10 mL/h), cell high viability, high purity	Require electric field frequency	[90]
	ODEP	Optically induced dielectrophoretic force-based cell manipulation in a microfluidic system (size-based separation)	63.6–85.6%	Recovery of a heterogeneous population of CTCs, label-free, high cell viability, high purity	Specific cell types and specific parameters require electric field frequency.	[91]
(B)
Category	Typical Platform	Description	Capture Efficiency	Advantages	Disadvantages	References
Positive selection	Cell Search®	EpCAM antibody-coated magnetic beads + immunostaining	42–90%	(FDA)-cleared CTC detection technique	Low sensitivity, loss of CTCs	[11,17]
	AdnaTest	Immunomagnetic beads (cocktail antibody) + PCR	60–80%	Providing molecular characteristics of CTCs	High contamination of WBCs	[94,95]
	MagSweeper	A rod coated with EpCAM antibody-labeled magnetic beads	60–70%	High purity, high throughput (9 mL/h)	Expensive, loss of CTCs	[96]
	Isoflux	EpCAM antibody-coated beads in a microfluidic chip	73–81%	High purity, high cell viability	Time-consuming	[97]
	MACS	Immunomagnetic bead separation	40–90%	Low-cost, technically simple	Time-consuming, high cell loss, low purity (around 50%)	[98]
	CTC-chip	Microfluidic chip of microposts conjugated with anti-EpCAM antibody	60–90%	High capture specificity, high purity	Low throughput (1 mL/h)	[99]
	Herringbone chip	EpCAM antibody-coated microfluidic chip + immunofluorescence microscopy	>90%	High throughput (4.8 mL/h)	Low purity of captured CTCs (around 14%)	[100]
Negative selection	RosetteSep	Blood cells depletion by pelleting the RBC-WBC crosslinked immunorosettes	40–62.5%	High specificity, recovery of a heterogeneous population of CTCs,	Time-consuming, exclusion of CTC-WBC clusters	[101]
	EasySep	Immunomagnetic beads and anti-CD45 antibodies for WBC removal	19–65%	High throughput (1–4 mL/h), simple operation, recovery of a heterogeneous population of CTCs,	Variable recovery, exclusion of CTC-WBC clusters	[102,103]
	CTC-iChip	Incorporates the unique-designed DLD (deterministic lateral displacement) microstructure arrays, inertial focusing, and MACS	>90%	High throughput (8 mL/h), recovery of a heterogeneous population of CTCs,	Low purity of captured CTCs (around 8%)	[103]