NPPA and hepatocellular carcinoma: Excised liver tissues from four HCC patients were incubated with F12+-ANP-Gal in PBS buffer (pH 7.4) for 3 h to allow efficient internalization and activation by H2S. After being washed with PBS buffer, whole specimens were irradiated with the 808-nm laser (1 W cm−2, 1 min); the resulting afterglow and fluorescence images were acquired immediately (Fig. 7a).