Fabrication of Metal and Metal Oxide Nanoparticles by Algae and their Toxic Effects

Table 3 Categorization of nanoparticles based on the toxicity values (EC50 or MBC, mg compound l⁻¹) to bacteria, protozoa and algae. All nanoparticles were tested in nominal concentrations from 0.01 up to 100 mg l⁻¹ [65]

EC₅₀ or MBC, mg compound l⁻¹	72 h EC₅₀	24 h EC₅₀	30 min EC₅₀	24 h MBC	24 h MBC
Organisms	Algae	Protozoa	Bacteria	Bacteria	Bacteria
Species	Pseudokirchneriella subcapitata	Tetrahymena thermophila	Vibrio fischeri (G⁻)	Escherichia coli (G⁻)	Staphylococcus aureus (G⁺)
Exposure Medium	Mineral Medium	DI Water	2 % NaCl	DI Water	DI Water
0.1–1	CuO, ZnO, Pd	None	None	CuO	CuO
>1–10	Co₃O₄, Fe₃O₄, Mn₃O₄, TiO₂	CuO, ZnO	CuO	ZnO, Pd	ZnO
>10–100	Al₂O₃, SiO₂, _WO3	Fe₃O₄, TiO₂	ZnO, Pd, WO₃, Sb₂O₃	Co₃O₄, Fe₃O₄	Fe₃O₄, Mn₃O₄, Pd
>100	MgO, Sb₂O₃	Al₂O₃, Co₃O₄, MgO, Mn₃O₄, Pd, Sb₂O₃, SiO₂, WO₃	Al₂O₃, Co₃O₄, Fe₃O₄, MgO, Mn₃O₄, SiO₂, TiO₂	Al₂O₃, MgO, Mn₃O₄, Sb₂O₃, SiO₂, TiO₂, WO₃	Al₂O₃, Co₃O₄, MgO, Sb₂O₃, SiO₂, TiO₂, WO

EC ₅₀ half effective concentration, MBC minimal biocidal concentration, i.e., the lowest tested nominal concentration of nanoparticles which completely inhibited the formation of visible colonies after sub-culturing on toxicant-free agarised growth medium. Prior sub-culturing bacteria were incubated with nanoparticles for 24 h at 25 °C in deionized water