Fig. 4. Fluorescence emission spectra (A) and histogram (B) of the fluorescence intensity of the supernatant of PS-PEG-Pep after cleavage by trypsin (2 mg mL⁻¹, 1 h) under different pH environments; (C) fluorescence emission spectra of PS-PEG-Pep after cleavage by trypsin (2 mg mL⁻¹, pH = 7.4) at different times and (D) relationship between the fluorescence intensity and cleavage time.