Table 2.

Metal oxide NPs with anticancer activity by direct action on tumor cells in different in vitro studies. HNSCC, head and neck squamous cell carcinoma.

Metal Oxide	In Vitro Model	NP Size	Organ Origin	Authors	Reference
Cerium oxide	Pancreatic cancer cell line L3.6pl	5–8 nm	Pancreas	Wason et al., 2013	[26]
Cerium oxide	Non-small cell carcinoma NCI-H460 DLD1 and HT-29 adenocarcinoma	4 nm	Lung colon/rectum	Pešić et al., 2015	[31]
Cerium oxide	A375 melanoma cells	5 nm	Skin	Sack et al., 2014	[32]
Cerium oxide	Squamous carcinoma cell lines SCL-1	3–5 nm	Skin	Ailili et al., 2013	[35]
Copper oxide	HeLa cells from human cancerous cervical tumor and B16-F10 melanoma cells from mice	40–110 nm	Cervix skin	Wang et al., 2013	[54]
Copper oxide	HepG2 cells	22 nm	Liver	Sidiqqui et al., 2013	[54]
Copper oxide	A549 adenocarcinomic human alveolar basal epithelial cells	577 nm	Lung	Sankar et al., 2014	[48]
Iron oxide	Caco-2 cells MCF-7 cells	9–20 nm	Colon breast	Klein et al., 2014	[17]
Titanium oxide	Human bladder cancer cell line T24, HeLa and human myeloid leukemia cell line U937	21 nm	Bladder blood	Thevenot et al., 2008	[20]
Zinc oxide	T98G human glioblastoma cells	13 nm	Brain	Wahab et al., 2013a	[36]
Zinc oxide	HNSCC carcinoma cell lines	74 nm	Neck	Hackenbert et al., 2010	[45]