Table 1.

Summary of iron oxide magnetic nanoparticle (MNPS) toxicity. Extensive amount of work is going on in area of toxicity studies of MNPs in various different combinations with appropriate enhancement with ligands, antibodies, polymeric coating, green synthesis, infusion of drug, hyperthermia application and external magnetic control with retention in superparamagnetism to be able to detect and direct MNPs at desired location. With many papers coming up each year in the field we have compiled a list of papers from year 2015–2019 to indicated the different types of (iron oxide) MNPs used in different kind of models recently to study the toxicological response of these MNPs.

Type of MNPs	Size and Shape of Tested MNPs	Model Organism (In Vitro or in Vivo Test)	Method of Toxicity Analysis	Treatment Condition (Time and Dose)	Results	Ref.
Uncoated Magnetic Nanoparticles (MNPs)
Bare Fe3O4-MNPs	72.6  ±  0.6 nm spheroid	THP-1 cells and female CD(R) IGS rats	Biochemical marker in rat blood after treatment	In vitro: 100, 800 and 1600 μg/mL 24 h In vivo: 12 mg/kg/intravenous injection 6 days	Fe3O4-MNPs cytotoxicity in erythrocytes in vitro and in vivo	[79]
	15 nm	Adult zebrafish	Behavioral and biochemical assessment in adult zebrafish	14 days waterborne incubation at 1 and 10 ppm	Uncoated MNPs exhibited behavior and biochemical safety at 1ppm but display neurobehavioral toxicity at 10 ppm	[80]
	15 nm and 225 nm spherical	A549 cells and Male Balb/c mice	Cell viability assay	In vitro:10–80 μg/mL In vivo: Subcutaneous injection of 2 × 106 cells suspended in 100 µL PBS	Magnetic nanomaterials did not indicate inherent toxicity	[81]
Surface coated/modified MNPs
(OC-Fe3O4) NPs (Fl-SiO2)	8 nm, 25 nm and 50 nm	BeWo b30 placental barrier model	Lactase dehydrogenase (LDH) in cell culture	4, 24 or 48 h 75, 15, 3, 0.6 and 0.12 µg/cm2	Iron oxide MNPS triggers cytotoxicity at lower doses and shorter exposure compared with silica NPs	[82]
CSO-INPs	6 ± 1.2 nm 8 ± 2.7 nm	HeLa, A549 and HeK293 cells	MTT assay	24, 48 and 72 h 0.5, 2, 4 μg/µL	INPs triggers toxic effects in Hek293, A549 and Hela cells in comparison to CSO-INPs	[83]
L14@Fe3O4 L4@Fe3O4 Gly@Fe3O4	11 ± 3 nm 7 ± 2 nm 9 ± 2 nm spherical	HeP G2 cells	MTT assay	24 and 48 h 1–500 μg/mL	Cytotoxicity of naked SPION increased in relation to increasing concentration	[84]
Fe2O3-NPs PEI-NPs PAA-NPs	28–30 nm	Male and female Crl:CD1(ICR) (CD-1) mice	Dams: gestation period of toxicity Cesarean: Histopathology analysis	Gestation day 8, 9, or 10 low dose:10 mg/kg high dose:100 mg/kg	A low dose of NPs, regardless of charge, did not induce toxicity; high exposure led to charge-dependent fetal loss	[85]
(HLC) Fe3O4 NPs	8.4 nm spherical	NIH3T3 cells	FluoStar Optima microplate reader	24 h 25 to 250 μg/mL	Reduced toxicity towards normal cells, enhancing the potential of magnetic hyperthermia in cancer treatment	[86]
DMSA-SPION	15 nm	MCF-7 cells	MTT assay Trypan blue exclusion test	1 h–72 h 0.4 mg/mL	MCF-7 accumulated NPs without effect on cell morphology, ROS generation and cell viability	[87]
Dox-gold coated MNPs MGNPs-DOX-M-group	MNP: 10 nm MGNPs: 22 nm spherical	Ehrlich ascites carcinoma cells injected intraperitoneally into female Balb/c mice	Histological examination Tumor size (AST, ALT, CK-MB, LDH)	20 mice group 10 mg/kg/group external application of neodymium–iron–boron magnetic disc (1.14 T) at tumor site for 3 h	Best therapeutic anti-cancer activity and lowest systemic toxicity compared to free DOX	[88]
PLGA NPs sorafenib SPION SRF/FA-PEG-PLGA NP	205 ± 3 nm spherical	BEL7402 cancer cells	MTT assay Apoptosis assay Anticancer efficacy	72 h 10 and 40 mg iron/mL	Concentration dependent cytotoxicity in BEL7402 cancer cells	[89]
Starch- Fe3O4 MNPs Dextran-Fe3O4 MNPs	100 nm	Rat PC 12 cells (ATCC)	Cell-viability assay	1 h–72 h 0.01–0.5 mg/mL	Uncoated- Fe3O4 MNPs maximum interaction and entered inside cell with no cytotoxic effect	[90]
Fe3O4/salicylic acid NPs	MNPs 33–277.9 nm Embryos injected: 60.3 nm and 79.9 nm MNPs	chick embryo chorioallantoic membrane model (CAM)	Morphological analysis	24 h Autopsied to harvest embryo viscera (heart, kidney, liver, and lung). 0.15 mL MNPs	50–100 nm diameter range MNPs had no embolic risk, on a safety intravenous administration. Tissue MNPs deposits were biocompatible with embryos and chicken	[91]
PEI-MNP	Not available	Human neuroblastoma SH-SY5Y cells (ATCC CRL-2266)	Quantitative/qualitative flow cytometry of apoptosis and necrosis	External hyperthermia (EHT), Magnetic hyperthermia (MHT)	A maximum difference in cytotoxicity approximately 45% was observed at T0 = 46 °C.	[92]
AA coated IONPs	3.98, 4.09, 3.41, 4.32, 2.35 nm globular	HFF2 cell lines	MTT assay	72 h 0.049, 0.073, 0.110, 0.165, 0.248 and 0.373 mg/mL	IONPs were biocompatible and nontoxic with the cell line HFF2	[93]
Multifunctional MNPs Anti-CD47 antibody Gemcitabine	109 ± 1 nm	CD47-positive pancreatic cancer cells	Resazurin dye	24 h Free Gem (0.1, 0.4 and 1 µM) MNP-Gem and MNP Gem-anti-CD47 (0.2 mg Fe/mL, 4.8 µM Gem, Ab 20 μg/mg Fe)	Cytotoxic activity of the multifunctional Nano formulation is not increased in the in vitro studies	[94]
Rosi-MNPs Al-MNPs Un-MNPs	21 ± 4 nm	Magnet and Sham mice	MTT assay	24 h 48 h 0.5, 5, 50, and 500 μg/mL	Al-MNPs only caused a significant reduction in cell viability at 500 μg/mL	[95]
MTX F-Lys-MTX NPs	43.72 ± 4.73 nm	MCF-7 cell lines	MTT assay	48 and 72 h 100 mL	MTX-conjugated NPs: reduction in cellular viability in human breast cancer (MCF-7) cells compared to free MTX over time	[96]
F@Tyr NPs F@Tyr@TMX NPs	22.19 ± 3.58 nm	HEK-293 MCF-7 cells	Hemolysis test and MTT assays	72 h F@Tyr NPs, Bare Fe3O4 0.025, 0.05, 0.1, 0.2, 0.4 and 0.8 mg/mL	Cytotoxicity study, F@Tyr@TMX NPs exhibited more cytotoxic effects than free TMX	[96]
IONPs-PEG IONPs-PEI SEI-10 SMG-10 SMG-30	10–30 nm	SKOV-3 RAW 264.7 Nude mice BALB/c mice	LDH assay, Hemolysis, ROS, MMP Cell cycle analysis, in vivo bio-distribution, toxicity	Hemolysis: 200 µL, 4 h. In vivo biodistribution: dose of 1.5 mg Fe/kg. In vivo toxicity: 1.5, 2.5, or 5 mg/kg	No obvious toxicity was found for PEGylated IONPs in BALB/c mice, whereas PEI-coated IONPs exhibited dose-dependent lethal toxicity	[97]
F@BSA@CURNPs	56 ± 11.43 nm, spherical	HFF2 MCF-7 cells	Cell viability by MTT assay	72 and 96 h Serial dilution 15–950 µM	F@BSA@CUR NPs had much higher cytotoxicity against MCF7 cells	[98]
CS-DX-SPIONs	55 nm round shape	In vitro: Rat C6 glioma, human U87 glioma, and human cervix carcinoma HeLa cells and Male Wistar rats	Histology analysis	24 h In vitro: 1, 10, 50, and 150 μg/mL 1, 3, 6, 12 intravenous injections of PBS via tail vein; DX-SPIONs (Fe concentration of 2.5 mg/kg); CS-DX-SPIONs (Fe at 2.5 mg/kg).	Increase in surface charge of the NPs due to the chitosan coating enhanced the intracellular uptake of particles and thus increased their cytotoxic activity.	[99]
Asparaginase enzyme-immobilized on APTES modified MNPs	50–100 nm	In vitro: Reduction of acrylamide in food model system	Deactivation rate constant (Kd) of free and immobilized enzyme	Five cycles of pretreatment	It was found to be more than three-fold increase their thermal stability from free enzyme and retained 90% activity after fifth cycle	[100]
MnFe2O4 MnFe1 MnFe2	3–20 nm	Mouse microglial cell line N13 and Zebrafish embryos Male Balb/c mice	Teratogenicity assay	In vitro: 0.1 to 100 μg/mL In vivo: 0.01, 0.1, 1, 10, 100 μg/mL In vivo: Fe 1, Fe 2. PEGylated Cubic (20 nm)	No significant cytotoxicity, till 24 h; No mortality or malformations were observed in the embryos exposed to different doses of particles at 48 hpf. At 100 μg/mL high percentage of mortality 6 dpf	[101]
n-octyltriethoxysilane coated-MNPs	17.9 ± 3.9 nm 18.7 ± 4.4 nm	PC12 and ReN cell VM	Cell Viability LIVE/DEAD Staining Prussian Blue and Nuclear Fast Red Staining	24 h 4, 8, 16, and 32 µg	Coated MNPs decreased cytotoxic effects; Significant differences in toxicological profiles in two mammalian cell lines	[102]
Carbon-coated MNPs	24 nm	Adult zebrafish	Multiple behavioral and biochemical tests	1 and 10 ppm exposure for 14 days	Carbon-coated MNPs can significantly enhance its biosafety by reducing neurobehavioral toxicities compared to the bare MNPs	[103]