Figure 6: Fluorescence calibration curve of NPs-FS-Rh-Folate-NMC (back), NPs-OG-FS-Rh-NMC (red), and NPs-OG-FS-Rh-Folate-NMC (blue) at different pH values. The fluorescence intensity ratio of FS/Rh or (OG+FS)/Rh is plotted against pH.