Table 1.

Classes of Nanoparticles for Multimodality Biomedical Imaging and Theragnostics.

Class	Imaging Modality	NP Type	Composition	Shape	HD (nm)	Overall Charge [Core] Surface	Pros	Cons	Refs.
Inorganic / Organic Hybrid NPs	MRI / Multimodal Imaging	MION, CLIO, and SPIO	Ion oxide with polymer coating	Globular	5 - 200	[None] +, −	Conventional MRI contrast agents; EPR^*	Interference in imaging; EPR^*; difficulty in Rx payload; opsonization; potential toxicity	7,11,21
	MRI / Multimodal Imaging	Gold Nanorods & Nanoshells	Gold-containing nanostructures	Rod or Sphere	2 - 100	[None] +, −	Size tunability; photothermal therapy; sensitivity; NIR; EPR		67,71-74
	Optical / Multimodal Imaging	QDs	Semiconductor core/shell arrays	Globular	5 - 50	[None] +, −, +/-	Broadband absorption; size tunability; photostability; photoefficiency; targetability	UV decomposition; aggregation; RES uptake; high potential for toxicity	8,77-82
		Silica NPs	Ceramic silica photosensitizers	Globular	5 - 100	[None] +, −	Facile synthesis; solubility; photostability; size tunability; biocompatibility; targetability	Need contrast agents; aggregation; mechanical stability	95-97,154
		Molecular Dots	Calcium phosphate nanocolloids	Globular	20 - 100	[−] +, −	Facile synthesis; photostability; photoefficiency biodegradability; targetability	Need contrast agents; EPR; difficulty in Dx and Rx payload	101,102
	Multimodal Imaging	Fullerenes	Carbon- containing hollow structures	Sphere	1 - 5	[None] +, −	Thermal strength; electrical properties; antimicrobial ability	Poor water-solubility; aggregation; difficulty in purification, surface modification, and Dx and Rx payload; high potential for toxicity	55,56,106,15 5
		Carbon Nanotubes	Carbon- containing tubes	Cylinder	3 - 100	[None] +, −	Size tunability; mechanical strength; electrical properties		55,56,106,155
		Nanoshells and Nanowires	Metallic semiconductors	Sphere or Linear	10 - 300	[None] +, −	Size tunability; electrical properties; high-throughput screening; thermal ablation		108,109,111, 156
Organic NPs	Multimodal Imaging	Biological NPs	Naturally derived polymers and lipoprotein conjugates	Linear, Branched, Globular	10 - 300	[All] +, −, +/−	Biocompatibility; flexibility; biodegradability; targetability	Mechanical weakness; difficulty in size and degradability control	24,85,116-119
		Polymer Nanospheres	Repeatedly linear or branched units	Linear or Branched	1 - 1000	[All] +, −, +/−	Biodegradability; flexibility; size tunability; targetability	Need contrast agents; Dx and Rx payload	120,123-125
		Dendrimers	Repeatedly branched macromolecules	Branched or Globular	3 - 30	[All] +, −, +/−	Hydrophilicity; flexibility; size tunability; targetability; biocompatibility; renal clearance	Limited synthesis; need contrast agents; Dx and Rx payload	127-131
		Liposomes	Phospholipid bilayers	Spherical	50 - 1000	[All] +, −, +/−	Conventional drug delivery vehicles; large Dx and Rx payload; EPR	Need contrast agents; poor stability; EPR; opsonization	24,51,116,132-136

Dx: Diagnostic; EPR: Enhanced permeability and retention; HD: Hydrodynamic diameter; MRI: Magnetic resonance imaging; NIR: Near-infrared; Rx: Therapeutic.

EPR is desired for passive targeting systems, but undesirable for active targeting systems.