The fluorescence images of different levels of tumor-related proteases in T24 cells. The treated and untreated T24 cells were incubated with the four-color nanoprobe for 12 h at 37 1C. T24 cells were treated with amiloride to decrease the expression of uPA, treated with antipain to decrease the CTB expression and treated with ilomastat to inhibit the expression of both MMP-2 and MMP-7.