Table 1.

CTC isolation techniques.

	CTC Isolation Technique	Method	Advantages	Disadvantages
Label dependent isolation	Antibody conjugation to magnetic nanoparticles	Antibody linked to magnetic nanoparticles to isolate CTCs expressing specific marker	One assay with FDA approval; can use different antibodies to isolate different populations of cells	Low sensitivity; down-regulation of EpCAM markers during metastatic transformation can limit sensitivity
	Microfluidics	Controlled flow in microchip to enhance CTC binding to antibody coated microchip walls	High sensitivity with high cell viability	Only able to process small sample volumes
Label independent isolation	Filtration	Size-based separation with purification to isolate CTCs from other blood cells	Isolation regardless of surface marker expression	Requires large volumes; poor purity; pore clogging
	Microfluidics (not dependent on antibodies)	Flow through microchip to separate CTCs based on geometric properties	High sensitivity with high cell viability	Only able to process small sample volumes
	Density gradient separation	Centrifugation to separate CTCs from blood cells based on density	Efficient process; cell viability after isolation	Loss of cells (varying density when cells clump); often requires further isolation due to contamination with other blood cells
	Imaging	Fiber optic array laser scanning to visually detect CTCs	Enumeration of CTCs	Lacking precision
	Dielectrophoresis	Application of non-uniform electric field to isolate cells	High recovery rate and viability	Low purity of the isolated sample
	Inertial focusing	Fluid inertia at high flow rates to isolate cell populations	Recovery of viable cells	Requirement of pre-processing of sample

Abbreviations: CTC: circulating tumor cell; EpCAM: epithelial cell adhesion molecule.