(A) Quenching properties and recovery of NIR fluorescence intensities in various concentrations of the NS with or without addition of activated MMP-2. MMP specificity of the NS in solution (B,C). (B) Fluorescence emission kinetic spectra of the NS in the presence of various stimuli (MMP-2, 3, 7, 9 and 13, 14 nmol/L) following a 80 min incubation at 37 °C. Top: fluorescence image sections of a 96-well microplate containing different combinations. (C) Fluorescence emission spectra of the NS in the presence of various concentrations of activated MMP-2 (0.7, 1.75, 3.5, 7, 14 nmol/L) and MMP-2 (14 nmol/L) with MMP-2 inhibitor (blue line) following a 80 min incubation at 37 °C. Inset: MMP-2 standard curve; top: corresponding fluorescence image sections of a 96-well microplate. (D) In vitro cellular toxicity of the NS estimated with the MTT assay in SCC7 cells.