TABLE 3.

Different types of metal-oxides nAbts and their associated functions.

Metal-Oxides NPs (MO-NPs)		Size/shape	Conjugated antibiotic	Conjugate’s chemistry	Targeted bacteria	Target site	Mechanism of action	Reference
CeO2		5–20 nm, spherical	β-lactam (cefotaxime, imipenem, amoxicillin, clavulanate, ampicillin)	CeO2 NP or nanoceria possess defect sites on its surface and oxygen vacancies that can load high antibiotic molecules to be functionalized.	Klebsiella pneumoniae carbapenemase KPC (KP1/11), Escherichia coli HB101	Outer cell membrane	Increases the outer cell membrane permeability by passive diffusion of antibiotics; oxidative stress by Ce3+ or Ce4+ ions to the cell membrane.	Bellio et al. (2018)
Superparamagnetic NPs (Iron-oxide)	MnFe2O4	25 nm, spherical	Vancomycin (Van)	MnFe2O4 NPs were coated with chitosan (Ch) and PEGylated. Mn-O bond has multiple oxidation states, and Mn-O-Fe interacts as a metalloenzyme with the amide-amide hydrogen bonding of Van to form Van-PEG-Ch- MnFe2O4 NPs	Staphylococcus aureus (ATCC25923), Staphylococcus epidermitis (ATCC12228), Bacillus subtilis (ATCC1720), Escherichia coli (ATCC1399), Pseudomonas aeruginosa (ATCC1430), MRSA (ATCC33591)	Outer cell membrane	Intracellular proteins and Lactatedehydrogenase leakage from the cell membrane, oxygen-free radical generation, and disruption of mitochondrial functions. Slow, sustained release of Van-PEG-Ch-MnFe2O4 NPs require a lower concentration of Van to achieve the antibacterial activity, thus reduces the scope of antibiotic resistance development.	Esmaeili and Ghobadianpour (2016)
	Fe3O4	15–45 nm, oblong, rounded-rectangular	Tobramycin	Functional groups of alginate-coated Fe3O4 NPs conjugated with the primary amines (-NH2) group of tobramycin.	Pseudomonas aeruginosa	Outer layer of the biofilm	Unusually high negative surface charge of alginate coated Fe3O4 NPs undergo a diffusion process crossing the outer layer of biofilm, which is also negatively charged. Alginate (polymer) coating on iron-oxide NPs provides rapid bio-uptake by biofilm barrier and delivers tobramycin at the target site.	Armijo et al. (2020)