Table 1. Antimicrobial activity and potential mechanism of chemically synthesized IONPs^a.

NPs	Particle size (nm)	Shape	Precursor	Synthesis method	Coating Material	Con. (μg/mL)	Organism	ZOI (mm)	MIC (μg/mL)	MBC (μg/mL)	IC50 (μg/mL)	Mechanism	ref.
Fe3O4	∼254	Spherical	FeCl3·6H2O, FeCl2·4H2O, NaOH, DW & HCl	COP	RHL	NR	Escherichia coli (O157: H7)	∼9	64	128	NR	The RHL coated-Fe3O4@PVA@p-CoA/GA biosurfactant mediated the structural and confirmational changes on the cell surface. Moreover, the coating material intercalated with the DNA, inhibited the replication, transcription and translation process by generating ROS. The ROS induced oxidative stress that led to apoptosis of bacterial cells.	(87)
							Escherichia coli (O26: H11)	∼10	4	8
							Escherichia coli (O78: H10)	∼12	32	64
							Staphylococcus aureus (MSSA)	∼12	16	32
							Staphylococcus aureus (MRSA)	∼10	32	64
							Staphylococcus aureus (VRSA)	∼8	64	128
					RHL, PVA, GA, p-CoA	NR	Escherichia coli (O157: H7)	35	32	64
							Escherichia coli (O26: H11)	45	1	2
							Escherichia coli (O78: H10)	40	16	32
							MSSA	40	4	8
							MRSA	30	16	32
							VRSA	25	32	64
Fe2O3	36.1	Spherical	FeCl3·6H2O, TiCl4·2H2O, CTAB & NaOH	COP	PR	5000	Bacillus subtilis	13	NR	NR	NR	The Fe2O3 and TiO2 polyester nanocomposite enhanced the interaction with bacterial cell membranes. It created an ionic imbalance in the bacterial cell, resulting in cell apoptosis.	(88)
							Staphylococcus aureus	18
							Escherichia coli	13
							Pseudomonas aeruginosa	12
							Candida albicans	29
							Aspergillus niger	26
Fe3O4	48	Spherical	FeSO4, FeCl3, DW, NH4OH & HNO3,	COP	RHL	NR	Pseudomonas aeruginosa	NR	1000	NR	NR	Fe3O4 induced oxidative stress in the bacterial cell by producing ROS which caused cell death. Again, the Rhamnolipid-coated Fe3O4 interacted with extracellular polymeric substances (EPS), which could affect the hydrophobicity of bacterial cell surface and hinder biofilm generation.	(89)
							Staphylococcus aureus	NR	1000	NR
IO QDNPs	<80	Spherical	Fe (NO3)3.9H2O, argon gas, DW, ethanol & NaOH	COP and HDT.	NR	NR	Escherichia coli PTCC 1330	NR	1	NR	NR	The IO-QDNPs changed membrane potential and damaged the biological mechanism by interacting with the cell membranes and subunit of the ribosome. Again, ROS-mediated structural and confirmational changes in DNA were responsible for bacterial cell death.	(90)
							Staphylococcus aureus PTCC 1053	NR	0.5
							Serratia marcescens PTCC1621	NR	0.5
							Pseudomonas aeruginosa PTCC1074	NR	0.5
							Staphylococcus aureus PTCC. 1112	NR	1
							Micrococcus luteus PTCC. 1110	NR	4
							Bacillus subtilis PTCC. 1023	NR	0.5
							Staphylococcus epidermidis PTCC 1114	NR	0.5
Fe3O4	∼39.56	Spherical	FeCl2·4H2O, FeCl3·6H2O & NH4OH	COP	TiO2	NR	Escherichia coli	NR	150	NR	NR	TiO2-coated IONPs had potent toxicity against bacterial cells, so they exhibited antibacterial activity when they interacted with the cell membranes.	(91)
							Klebsiella pneumonia	NR	150
							Bacillus subtilis	NR	150
							Staphylococcus aureus	NR	150
							Escherichia coli	NR	150
							Klebsiella pneumonia	NR	150
							Bacillus subtilis	NR	150
							Staphylococcus aureus	NR	150
SPION	23.32 ± 1.17	NR	Iron salt and dimercaptosuccinic acid	Two-step COP process.	NR	NR	MARS	NR	530.796 ± 15.241	NR	NR	SPION mediated the conformational and structural changes on the proteins of the cell surface and disrupted the cell membrane.	(92)
									495.993 ± 3.909	NR
									581.353 ± 10.26	NR
									457.871 ± 21.064	NR
Fe3O4	31.09	Spherical	FeCl2·2H2O, FeCl3·6H2O, N2, DW & NH4OH.	COP	NR	NR	Staphylococcus epidermidis	17.33 ± 0.57	25	50	NR	Generally, photolytic generation of ROS induces oxidative stress in the cell. Also, due to the vibration of magnetic fields, IONPs lead bacterial cells to death.	(93)
							Proteus mirabilis	17.51 ± 0.57	50	100
							Acinetobacter baumannii	17.66 ± 0.57	50	100
					PEG	NR	Staphylococcus epidermidis	19.66 ± 0.57	25	50
							Proteus mirabilis	21.66 ± 0.57	50	100
							Acinetobacter baumannii	22.00 ± 0.46	50	100
					GEN	NR	Staphylococcus epidermidis	21.33 ± 1.15	50	100
							Proteus mirabilis	23.66 ± 0.57	25	50
							Acinetobacter baumannii	23.66 ± 0.57	50	100
					PEG+ GEN	NR	Staphylococcus epidermidis	23.66 ± 0.057	50	100
							Proteus mirabilis	25.66 ± 0.57	25	50
							Acinetobacter baumannii	26.33 ± 0.57	50	100
Fe2O3	14.2 ± 0.5	Spherical	FeCl2·4H2O, FeCl3·6H2O, DW, NH4OH, HNO3, HCl & Fe (NO3)3·9H2O	COP	Teicoplanin	NR	Bacillus subtilis (ATCC 6633)	NR	2	>128	NR	Fe2O3 NPs induced ROS, which induced oxidative stress and led to programmed cell death as well as autophagic activity.	(94)
							Staphylococcus aureus (ATCC 6538Pb (MSSA))	NR	2	128
							Staphylococcus aureus (ATCC 43300 (MRSA)	NR	2	>128
							Enterococcus. faecalis (ATCC 29212)	NR	1	32
							Enterococcus. faecalis (ATCC 51299 (VanB)	NR	2	>128
							Enterococcus. faecalis (9160188401-EF-34 (VanA)	NR	>128	>128
							Escherichia coli (ATCC 35218)	NR	>128	>128
Fe2O3	25.34	Hexagonal	FeSO4·7H2O, Co (NO3)2·6H2O, NaOH & DW	COP	NR	400	Bacillus subtilis	11	Escherichia coli			Fe2O3 NPs induced ROS, which triggered oxidative stress and led to cell death.	(59)
							Staphylococcus aureus	12	900	NR
							Escherichia coli	19
							Salmonella typhi	12
						600	Bacillus subtilis	15
							Staphylococcus aureus	13
							Escherichia coli	20
							Salmonella typhi	13
						800	Bacillus subtilis	17
							Staphylococcus aureus	15
							Escherichia coli	21
							Salmonella typhi	16
Fe3O4	10.64 ± 4.73	Spherical	FeSO4·7H2O, FeCl3·6 H2O, DW & NaOH	COP	Oleic acid	NR	Escherichia coli	NR	NR	NR	NR	The antibacterial activity of Fe3O4 NPs was mediated by electrostatic interaction between NPs and the cell membranes. Also, the ROS played a vital role in cell apoptosis.	(95)
							Enterococcus hirae	NR
Fe3O4	10–30	Spherical	NR	COP	NR	12.5	Escherichia coli	7	NR	NR	NR	Fe3O4 mediated antibacterial activity by causing damaged to the proteins and DNA in the bacterial cell by generating ROS.	(96)
							Proteus mirabilis	7
							Bacillus subtills	7
						25	Escherichia coli	7
							Proteus mirabilis	7
							Bacillus subtills	7
						50	Escherichia coli	8
							Proteus mirabilis	8
							Bacillus subtills	8
						Fe3O4 + Plant extract
						12.5	Escherichia coli	11	NR	NR	NR
							Proteus mirabilis	16
							Bacillus subtills	7
						25	Escherichia coli	12
							Proteus mirabilis	17
							Bacillus subtills	8
						50	Escherichia coli	13
							Proteus mirabilis	18
							Bacillus subtills	10
Fe3O4	6–9	Spherical	FeCl3, FeSO4, DW, NH4OH, PEG & ethyl alcohol	COP	NR	NR	Serratia marcescens	NR	32	NR	NR	ROS produced by IONPs moderated physical damage or chemical damage by interacting with the cell membranes, leading to bacterial cell death.	(97)
							Escherichia coli	NR	64
							Pseudomonas aeruginosa	NR	128
							Listeria monocytogenes	NR	32
Fe3O4	24	NR	FeCl3, FeCl2, DW, Argon gas & NaOH	COP	NR	40	Bacillus cereus	13	5	80	NR	IONPs could interact with DNA and proteins and mediate their conformational changes.	(66)
							Klebsiella pneumoniae	15
						80	Bacillus cereus	22
							Klebsiella pneumoniae	26
Fe3O4	10–14	Spherical	FeCl3, FeCl2, DW, & NaOH	COP	NR	500	Staphylococcus aureus	<10	Staphylococcus aureus		NR	The IONPs damaged the cell membrane by inducing ROS. When IONPs are conjugated with gentamicin, bacterial growth is constrained by both mechanisms. By inhibiting the protein synthesis and damaging the cell membrane.	(98)
							Escherichia coli	<10	25,000	30,000
							Bacillus subtills	<10
							Pseudomonas aeruginosa	<10
						1000	Staphylococcus aureus	<10	Escherichia coli		NR
							Escherichia coli	<10	28,000	35,000
							Bacillus subtills	<10
							Pseudomonas aeruginosa	<10
						3000	Staphylococcus aureus	<10	Bacillus subtills		NR
							Escherichia coli	<10	20,000	25,000
							Bacillus subtills	<10
							Pseudomonas aeruginosa	<10
						5000	Staphylococcus aureus	<10	Pseudomonas aeruginosa		NR
							Escherichia coli	<10	30,000	35,000
							Bacillus subtills	<10
							Pseudomonas aeruginosa	<10
					GEN	500	Staphylococcus aureus	<10	Staphylococcus aureus		NR
							Escherichia coli	<10	2000	3000
							Bacillus subtills	12.5
							Pseudomonas aeruginosa	<10
						1000	Staphylococcus aureus	10	Escherichia coli		NR
							Escherichia coli	<10	2500	3000
							Bacillus subtills	13
							Pseudomonas aeruginosa	<10
						3000	Staphylococcus aureus	13	Bacillus subtills		NR
							Escherichia coli	<10	1500	2500
							Bacillus subtills	25
							Pseudomonas aeruginosa	<10
						5000	Staphylococcus aureus	16	Pseudomonas aeruginosa		NR
							Escherichia coli	11	3000	4000
							Bacillus subtills	33
							Pseudomonas aeruginosa	<10
Fe3O4	∼100	Spherical	Oleic amine, ethylene glycol, FeCl3·6H2O, & sodium acetate	HDT	NR	200	Klebsiella pneumoniae	22 ± 1.0	Klebsiella pneumoniae		NR	IONPs generate ROS molecules that interact with the ion transportation channel and the DNA and induce oxidative stress to eliminate bacterial cells.	(68)
							Staphylococcus aureus	28 ± 0.5	50	100
							Enterococcus faecalis	25 ± 0.0
							Pseudomonas aureginosa	18 ± 1.0
						100	Klebsiella pneumoniae	20. ± 0.0	Staphylococcus aureus
							Staphylococcus aureus	25 ± 0.0	6.25	12.5
							Enterococcus faecalis	20 ± 1.0
							Pseudomonas aureginosa	16 ± 0.0
						50	Klebsiella pneumoniae	18 ± 1.0	Enterococcus faecalis
							Staphylococcus aureus	22 ± 2.0	6.25	12.5
							Enterococcus faecalis	17 ± 0.5
							Pseudomonas aureginosa	15 ± 0.5
						25	Klebsiella pneumoniae	15 ± 0	Pseudomonas aureginosa
							Staphylococcus aureus	20 ± 1.0	50	50
							Enterococcus faecalis	11 ± 0.0
							Pseudomonas aureginosa	12 ± 0.0
Fe3O4	35	Spherical	Fe (NO3)3·9H2O, DW, & NH3	CC	NR	25	Escherichia coli	15	NR	NR	NR	Fe3O4 generated ROS that disrupted membrane protein and penetrated the bacterial membrane. It induced oxidative stress, which led to cell death.	(99)
							Proteus vulgaris	11
							Staphylococcus aureus	9
							Xanthomonas	10
						30	Escherichia coli	16
							Proteus vulgaris	12
							Staphylococcus aureus	12
							Xanthomonas	12
						40	Escherichia coli	17
							Proteus vulgaris	15
							Staphylococcus aureus	14
							Xanthomonas	14
						50	Escherichia coli	17
							Proteus vulgaris	20
							Staphylococcus aureus	15
							Xanthomonas	15
						60	Escherichia coli	15
							Proteus vulgaris	20
							Staphylococcus aureus	11
							Xanthomonas	8
						80	Escherichia coli	15
							Proteus vulgaris	12
							Staphylococcus aureus	12
							Xanthomonas	14
						100	Escherichia coli	21
							Proteus vulgaris	21
							Staphylococcus aureus	15
							Xanthomonas	15
IO	14–23	Hexagonal	FeSO4·7H2O, β-Cyclodextrin, N2 & sodium borohydride	CS	Beta-cyclodextrin	NR	Staphylococcus aureus	43.83 ± 0.75	100	NR	NR	IONPs interacted with the cell wall and facilitated cell permeability, hindering cellular activity and resulting in the disruption of bacterial cells.	(100)
							Klebsiella pneumonia	39.83 ± 1.33	300
							Salmonella typhi	20 ± 0.63	200
Fe3O4	∼25	NR	Fe (NO3)3, DW, Ethylene glycol.	SG	NR	5	Bacillus spp.	23	NR	NR	NR	The addition of citric acid increased the ROS generation and the electro-hole pair generation, leading to the decay of the bacterial surface.	(101)
							Escherichia coli	19
						10	Bacillus spp.	25
							Escherichia coli	20
						15	Bacillus spp.	26
							Escherichia coli	21
						20	Bacillus spp.	27
							Escherichia coli	22
					Citric acid	5	Bacillus spp.	32
							Escherichia coli	29
						10	Bacillus spp.	31
							Escherichia coli	22
						15	Bacillus spp.	33
							Escherichia coli	23
						20	Bacillus spp.	36
							Escherichia coli	26
Fe3O4	NR	NR	Fe (NO3)3·9H2O, ethanol	SG	NR	50	Enterobacter aerogenes	NR	NR	NR	NR	Fe3+ ions interact with the negatively charged membrane, decreasing the membrane integrity. By entering the cell, IONPs produce ROS, which disrupts the cell organelles and eradicates the cell.	(102)
						100
						150	Staphylococcus aureus
						200
Fe2O3	50–110	Spherical	SDS, DMF & iron pressed pellet.	PLA	NR	Fe2O3 + DMF						The electrons in the photocatalytic process were absorbed by free radicals and produced OH– radicals. These radicals inhibited the growth of bacteria by induced oxidative stress generated by ROS.	(103)
						4250 (20 mJ)	Escherichia coli	19	NR	NR	NR
							Pseudomonas aeruginosa	17
							Serritia marcescens	20
							Staphylococcus aureus	21
						4250 (40 mJ)	Escherichia coli	22
							Pseudomonas aeruginosa	16
							Serritia marcescens	24
							Staphylococcus aureus	18
						4250 (60 mJ)	Escherichia coli	18
							Pseudomonas aeruginosa	27
							Serritia marcescens	17
							Staphylococcus aureus	22
						4250 (80 mJ)	Escherichia coli	17
							Pseudomonas aeruginosa	27
							Serritia marcescens	20
							Staphylococcus aureus	23
						Fe2O3 + SDS
						4250 (20 mJ)	Escherichia coli	25
							Pseudomonas aeruginosa	13
							Serritia marcescens	27
							Staphylococcus aureus	30
						4250 (40 mJ)	Escherichia coli	27
							Pseudomonas aeruginosa	27
							Serritia marcescens	30
							Staphylococcus aureus	35
						4250 (60 mJ)	Escherichia coli	23
							Pseudomonas aeruginosa	22
							Serritia marcescens	15
							Staphylococcus aureus	28
						4250 (80 mJ)	Escherichia coli	20
							Pseudomonas aeruginosa	19
							Serritia marcescens	18
							Staphylococcus aureus	30

^aNPs: Nanoparticles; Con.: Concentration; ZOI: zone of inhibition; ref: References; ROS: Reactive oxygen species; NR: Not reported; MIC: Minimum inhibitory concentration; MBC: Minimum bactericidal concentration; IC₅₀: Half maximal inhibitory concentration; COP: Coprecipitation; HDT: Hydrothermal; CS: Chemical synthesis; SG: Sol–gel; TDP: Thermal decomposition; PLA: Pulsed laser ablation; FeCl₃·6H₂O: Ferric chloride hexahydrate; FeCl₂·4H₂O: Ferrous chloride tetrahydrate; FeSO₄: Ferrous sulfate; TiCl₄·2H₂O: Titanium tetrachloride; FeSO₄·7H₂O: Ferrous sulfate; Fe (NO₃)₃·9H₂O: Ferric nitrate nonahydrate; DW: Deionized water; CTAB: Trimethylammonium bromide; PR: polyester resin; RHL: Rhamnolipid; DMF: Dimethylformamide; GEN: Gentamicin; kan: Kanamycin; CC: Chemical combustion; PEG: Poly(ethylene glycol); IO: Iron oxide; QNDPs: Quantum dots nanoparticles; SPION: Superparamagnetic Iron oxide nanoparticles; PVA: Poly(vinyl alcohol) polymer; GA: Gallic acid; p-CoA: p-Coumaric acid; RHL coated-Fe₃O₄@PVA@p-CoA/GA: Rhamnolipid coated Iron oxide with Poly(vinyl alcohol) polymer; Gallic acid & p-Coumaric acid; MSSA: Methicillin-sensitive Staphylococcus aureus; MRSA: Methicillin-resistant Staphylococcus aureus; VRSA: Vancomycin-resistant Staphylococcus aureus.