Table 2.

Overview of NP-based CTC detection methods

Nanomaterial	Pros	Cons	References
MNPs/nanoclusters	Biocompatibility, magnetic separation, high sensitivity	Magnetic aggregation; dependence on binding capacity of MNPs (affinity-based)	42, 109–112
Fe-core MNPs	High magnetic moments, superparamagnetic	Rapid oxidation → protective shells needed	57
Magnetic–optical bifunctional NPs	Simultaneous detection and isolation of various tumor-cell types, killing by X-ray-based detection possible	Affinity-based	53
Micro-NMR	Rapid, highly sensitive biomarker detection, only minimal sample purification necessary	Variation in NMR frequency depending on temperature	57
Quantum dots	Quantitative detection with high sensitivity, various fluorescence types enable capture of heterogeneous CTCs	Toxicity affects viability (no further investigations possible), intermittence under continuous excitation	21, 53
Gold NPs	Microsurgical removal/laser-controlled detection and direct ablation of CTCs, postcapture analysis	Nonbiodegradability, complicated preparation	21, 53, 113, 114
Graphene/graphene oxides	High specificity, multiplex functionalization, label-free detection, high conductivity, no toxicity, easy functionalization	Aspecific cellular internalization, hybrid sensors not reproducible yet	21, 53, 92, 115–118
Liposomes	Biocompatibility, long blood-circulation time	Low stability	21, 119, 120
Polymeric nanomaterials	Biocompatibility and biodegradability, ease of chemical modification, drug encapsulation/conjugation, improves sensitivity/selectivity of surfaces for CTC detection	Low stability	53, 97, 121
Hybrid NPs	Recovery of viable cells, can proliferate in vitro	Different hybrid NPs for different types of CTCs necessary, all trials still in vitro	100
SWCNTs/MWCNTs	High stability, bioactivity, capable of cell capture, high sensitivity, even in whole blood	One type of aptamer binds only one specific target	122
Microfabricated filters	Label-free, unbiased	Sensitivity to size	12, 42
Microfluidic-enabled immunoseparation	High efficiency, sensitivity, throughput, automatic, further molecular analysis	Relied on microscopy imaging for CTC identification after isolation	12, 36, 42, 65, 123
Herringbone chip	Transparent device for better imaging		12, 36, 116
CTC chip	High throughput, combination of immunomagnetic sorting with micropost-based enrichment		12, 36, 116, 124
Micro–Hall detector	Rapid detection, high contrast against blood cells, detection of multiple biomarkers	Limited throughput (about 107 cells)	124, 125
Gilupi nanodetector	Large volume analyzed	Affinity-based, complex procedure	12, 36

Note: Data from Zhang and King.²¹

Abbreviations: MNPs, magnetic nanoparticles; CTC, circulating tumor cell; SWCNTs, single-walled carbon nanotubes; MWCNTs, multiwalled CNTs; NMR, nuclear magnetic resonance; NP, nanoparticle.