Table 1.

Important components of NP toxicity testing

Characterization	Primary particle size
	Agglomerate size in suspension
	Size distribution range
	Elemental composition & contaminant levels
	Zeta potential
	Particle shape/morphology & density
Dosage metrics	Mass per volume (mg/mL)
	Surface area (μm3)
	Particle number
	Single or multi-dose & dose frequency
Model system	In vitro: cell selection, mono- or co-culture model
	In vitro: assay selection (MTT, LDH, etc)
	In vivo: animal selection (rat, mouse, etc)
	In vivo: method of exposure (inhalation, intra-tracheal instillation, injection, internal wear debris, etc) & exposure duration
	In vivo: sample collection (fluid, tissue, organ, etc)

Abbreviations: LDH, lactate dehydrogenase; NP, nanoparticle.