. 2010 Dec;2(12):a003848. doi: 10.1101/cshperspect.a003848

Table 2.

Overview of agents

Class	Subtype	Examples	Substrate	Primary use	Ex/Em	Turn-on/shift	Clinical	Modality	Limitations
Genetic tags	GFP	eGFP	NA	Fusion, reporter	484/507	Yes	No	IVM	Limited to proteins; no human use
	RFP	mCherry	NA	Fusion, reporter	587/610	Yes	No	IVM	lower QY compared to GFP
		mRaspberry	NA	Fusion, reporter	598/625	Yes	No	IVM, FMT	lower QY compared to GFP
		Katushka	NA	Fusion, reporter	588/635	Yes	No	IVM, FMT	lower QY compared to GFP
		IFP	Biliverdin	Fusion, reporter	684/708		No	IVM, FMT	Emerging
	Photo- conversion	Dendra	NA	Cytoplasmic,	490/507 green		No	IVM	No human use
				Cell position	553/573 red
	Luciferases	Firefly	Luciferin	Reporter	broad em	Yes	No	BLI	Limited to proteins; no human use
		Renilla	Coelenterazine	Reporter	broad em	Yes	No	BLI	Limited to proteins; no human use
		Gausia	Coelenterazine	Reporter	broad em	Yes	No	BLI	Limited to proteins; no human use
Antibodies	IgG	EGFR	NA	Cell surface marker	TD	Possible	Yes	PET, IVM, FMT	Delivery barriers; limited efficacy in vivo
		Her2/neu	NA	Cell surface marker	TD	Possible	Yes	PET, IVM, FMT	Delivery barriers; limited efficacy in vivo
	Fragments	Fab	NA	Cell surface marker	TD	Possible	Yes	PET, IVM, FMT	Delivery barriers; kinetics
		Diabody	NA	Cell surface marker	TD	Possible	Yes	PET, IVM, FMT	Delivery barriers; kinetics
		Minibody	NA	Cell surface marker	TD	Possible	Yes	PET, IVM, FMT	Delivery barriers; kinetics
Small molecules	Metabolites	FDG, FLT, acetate	NA	Metabolism	TD	No	Yes	PET	Limited number agents
		Steroids	NA	Reporter	TD	No	Yes	PET	Limited number agents
		Hyperpolarized Molecules	NA	Metabolism	—	—	Yes	MRI	Time limitation
	Drugs	Taxol-NBD	NA	Intracellular targets	TD	Possible	No	PET, IVM, FMT	Limited number of high affinity agents
	Prodrugs	Cathepsins, luminol	NA	Enzymes	TD	Yes	Yes	FMT, BLI	Limited number of high affinity agents
	Peptides	RGD, collagen	NA	Receptors	TD	No	Yes	PET, IVM, FMT	Limited number of high affinity agents
	Tags	CFSE, VT680	NA	Cell tags	TD	Yes	No	IVM, FMT	Ex vivo labeling
		Cy dyes	NA	Generic labeling	TD	Yes	Planned	IVM, FMT
	Environment	pH	NA	Hypoxia, endosomes	TD	Yes	No	IVM, FMT	Limited number of high affinity agents
Nanotechnology	Q-dot	CdSe	NA	Cell surface marker	TD	Yes	No	IVM, FMT	Possible delivery barriers
	Magnetic	MION	NA	Macrophages	TD	DMR	Yes	MRI	Possible delivery barriers
		CLIO	NA	Cell surface marker	TD	DMR	No	MRI	Experimental use only
		Ferumoxytol	NA	Macrophages	TD	DMR	Yes	MRI	Possible delivery barriers
	Polymers	Prosense	NA	Proteasses	TD	Yes	Planned	FMT	Possible delivery barriers
		Angiosense	NA	Vascualrity	TD	No	No	FMT	Experimental use only
	Bionano	Phage	NA	Cell surface marker	TD	No	No	FMT, MRI	Experimental use only
Bioorthogonal	Staudinger	triarylphosphine	Azide	Proteins, carbohydrate	TD	No	No	IVM	Limited in vivo experience
	3,2 click	alkyne	Azide	Proteins	TD	No	No	FMT, IVM, PET	Limited in vivo experience; reaction slow
	4,6 Click	Norbornene	Tetrazine	Many targets	TD	No	No	FMT, IVM, PET	Emerging
		TCO	Tetrazine	All targets	TD	Yes	Planned	FMT, IVM, PET	Emerging

TD = depends on attached fluorochrome (VT, Alexa, Cy, etc.) or other tracer (¹⁸F, ¹¹C).