Table 1.

Contrast agents for photoacoustic imaging.

Photoacoustic Contrast Agent	Type	Absorption Peak (nm)	Size (nm)	Modification Application	Application	Ref.
Indocyanine-green	NIR Fluorescent Dye	810	<2	CarbonNanotube, PEG, PEBBLEs	PAT, in tissue phantoms and in vivo	[7,16,17,18,19]
Methylene blue	NIR Fluorescent Dye	650–700	<2		PAT, in tissue phantoms	[15]
Alexa Fluor 750	NIR Fluorescent Dye	750	<2		Multispectral PAI, in vivo	[8,9]
IRDye800CW	NIR Fluorescent Dye	750–800	<2	NPR-1	PAS, in vivo	[13]
IRDye800-c(KRGDf)	NIR Fluorescent Dye	750–790	<2	Integral proteinαvβ3	PAS, in vivo	[20]
Evans Blue	NIR Fluorescent Dye	550	<2		PAT, in vivo	[10]
PPCy-C8	NIR Fluorescent Dye	754–789	<2	Perfluorocarbon	In vivo, dual-modality PAI-FI	[21]
Cypate-C18	NIR Fluorescent Dye	754–790	<2	Perfluorocarbon	In vivo, dual-modality PAI-FI	[21]
Caspase-9 Probe	NIR Fluorescent Dye	640	<2		PAI, in vivo	[11]
MMPSence™ 680	NIR Fluorescent Dye	620, 680	<2		PAI, in tissue phantoms	[14]
BHQ3	Quencher	672	<2		PAI, in vitro	[12]
QXL680	Quencher	680	<2		PAI, in vitro	[12]
Au Nanospheres	Plasmonic Noble Metal Nanoparticle	520–550	20–80	PEG	PAT, in vivo	[22,23]
Au Nanoshells	Plasmonic Noble Metal Nanoparticle	700–1100	50–500	PEG	PAT, in vivo	[24,25]
Au Nanorods	Plasmonic Noble Metal Nanoparticle	550–1550	a few to hundreds of	HER2, EGFR	PAI, in vitro	[26,27,28]
Au Nanocages	Plasmonic Noble Metal Nanoparticle/Theranostic Contrast Agent	820	25		PAT, in vivo, photothermal therapy	[29,30,31]
Au Nanoclusters	Plasmonic Noble Metal Nanoparticle	500–550	100		PAI, in vitro	[32,33]
Au Nanostars	Plasmonic Noble Metal Nanoparticle	767	120		PAT, in vivo	[34,35]
Au Nanobeacons	Plasmonic Noble Metal Nanoparticle	520	150	αvβ3	PAT, in vivo	[36,37]
Ag Nanoplates	Plasmonic Noble Metal Nanoparticle	550–1080	25–218	a-EGFR, PEG	PAI, in vivo	[38]
Ag Nanosystems	Plasmonic Noble Metal Nanoparticle/Theranostic Contrast Agent	400–500	180–520		PAI, ex vivo; image-guided therapy	[39]
Quantum dots	Nanoparticles Based On Other Principles	400–750	<10		PAT, in vivo: Triple-modality PA-PT-Fluorescent	[40]
Nanodiamond	Nanoparticles Based On Other Principles	820	68.7		PAI, in vivo	[41]
Polypyrrole Nanoparticles	Nanoparticles Based On Other Principles	700–900	46		PAI, in vivo	[42]
Copper Sulfide	Nanoparticles Based On Other Principles	900	11 ± 3		PAI, in vivo	[43]
Graphene Nanosheets	Nanoparticles Based On Other Principles	200–900	10		PAI, in vitro	[44]
Iron Oxide-gold Core-shell	Multimodality Contrast Agent	660–900	1–5		Triple-modality MRI-PAI-mmPA	[45]
Gd2O3	Multimodality Contrast Agent		100	DEG, gelatin	In vivo, dual-modality PAT-MRI	[46]
Single-walled Carbon Nanotubes (SWNT)	Multimodality Contrast Agent	785	5–8	Protamine, PEG	In vivo, Triple-modality Raman- MRI-PAI	[47]
Dye-loaded Perfluorocarbon-based Nanoparticles	Multimodality Contrast Agent	750–800	220 ± 11	cypate-C18, PPCy-C8,PEG2000, phosphatidylethanolamine	In vivo, dual-modality PAI-FI	[21]
AuMBs	Multimodality Contrast Agent	760	100–1000	HAS	Dual-modality PAI-UI	[48]
Triggered Nanodroplets	Multimodality Contrast Agent	750–800	300	Perfluorocarbon	In tissue phantoms and in vivo, dual-modality PAT-UI	[49]
Cobalt Nanowontons	Multimodality Contrast Agent	700	30–90		Dual-modality MRI-PAT	[50]
Nanoroses	Multimodality Contrast Agent	700–850	30		PAI, in vitro	[51]
MPRs	Theranostic/Multimodality Contrast Agent	532	120	maleimide-DOTA-Gd	In vivo, triple-modality MRI-API-Raman; image-guided surgery	[52]
Goldsilica Core shell Nanorods	Theranostic Contrast Agent	780	10.3 ± 1.1	PEG	PAI, in vitro	[53,54]
Superparamagnetic Iron Oxide (SPIO)	Theranostic Contrast Agent	500–780	80–150		PAI, ex vivo	[55]