Table 2.

Advantages and limitations of MNPs for nucleic acid delivery

Types	Advantages	Limitations	References
Gold	▪ Ability to regulate their size ▪ Complementary biocompatibility ▪ Shape and surface functionalization on the nano and molecular level ▪ Safety	▪ Difficulty of control the size and morphology	[117, 128]
Silver	▪ Antibacterial	▪ Genotoxicity ▪ Non-specific biological toxicity	[66, 128–130]
Iron oxide	▪ Biodegradability	▪ Nonreproducibility of the synthesis ▪ Agglomeration of the colloidal suspension	[131, 135, 144]
Magnetic	▪ Possibility for selective target site treatment ▪ Simple monitoring ▪ Assistant drug or gene release	▪ Toxicity ▪ Agglomeration (pH 7) ▪ Difficulty of control the size and morphology	[136–139]
Silica	▪ Capable of conjugating with almost ▪ all types of functional groups ▪ Biocompatibility	▪ Hemolysis ▪ Toxicity ▪ Difficulty of synthesis	[133–137]
Zinc oxide	▪ Anticancer activity	▪ Cytotoxicity	[155–159]
Copper oxide	▪ Surface and superior quantum size effect ▪ Volume effect and macroscopic quantum tunneling have effects in magnetic and chemical activity ▪ Optical absorption ▪ Thermal resistance ▪ Catalysis and the melting point	▪ Chemical methods synthesize suffer from the adsorption of toxic chemicals	[160–165]
Titanium	▪ Cellular uptake profile and stimuli-responsive	▪ Cytotoxicity	[166, 167]
Selenium	▪ Antioxidant in human health ▪ Superior biocompatibility ▪ Degradability in vivo	▪ Toxicity ▪ Biocompatibility	[168–171]
Palladium	▪ High porosity ▪ Photocatalytic activity ▪ Thermal and chemical stability	▪ Toxicity	[172–175]
Platinum	▪ Anticancer activity	▪ Cytotoxicity ▪ Low biocompatibility	[149, 176–178]