Figure 2: Protein coronas modulate sulphide formation.

Proposed mechanism of protein corona-modulated nano-Ag₂S formation at Ag NPs, with hard corona proteins trapping Ag⁺ released from the nanoparticle surface and soft corona proteins transporting said ions away from the sulphide-formation centres in the long-lived corona (a); TEM images of silver nanocubes after 24 h in RPMI-1640 cell culture medium supplemented with 1% FBS (b), followed by 6 days incubation in RPMI-1640 with 0% FBS (inset cartoon showing only hard corona around Ag NPs) (c), 1% FBS (d) or 10% FBS (e; common inset cartoon showing hard and soft coronas, as well as free bulk proteins around Ag NPs); TEM images of silver nanocubes after 7 days incubation in RPMI-1640 with 0.4 mg ml⁻¹ BSA (f) or 4 mg ml⁻¹ BSA (g) (common inset cartoon showing hard corona and free bulk proteins around Ag NPs); Ultraviolet–visible spectra of cubic (h) and quasi-spherical (i) Ag NPs after 24 h incubation in RPMI-1640 cell culture medium supplemented with 1, 10 or 50% FBS; TEM images of silver nanocubes after 24 h in RPMI-1640 supplemented with 1% FBS (j), 10% FBS (k) and 50% FBS (l). Scale bars are 100 nm (b, j–l) or 50 nm (c–g).