HPPH (Photochlor) (Photochlor) is a second-generation photosensitizer. It is used as photodynamic therapy (PDT) agent.

Cells treated with GO-PEG-HHPH displays a stronger fluorescence signal than those treated with free HPPH. In fact, the fluorescence of HPPH is rather weak. After 24 h, Fluorescence image of 4T1 cells incubated with 0.49 μg/mL GO-PEG, 1 μM HPPH (free HPPH), or equivalent amount of GO-PEG-HPPH (1 μM HPPH and 0.49 μg/mL GO-PEG). The cellular uptake of GO-PEG-HPPH and HPPH is investigated with 4T1 murine mammary cancer cells. The cells are incubated with GO-PEG-HPPH and free HPPH at equivalent HPPH concentration (1 μM) for 24 h and then observed with a confocal microscope [1].

A combination treatment regimen is devised in which Colo26-HA tumor-bearing BALB/c mice are treated with an HPPH-PDT regimen known to lead to enhanced anti-tumor immunity (0.4 μmoles/kg HPPH followed 18 h later by illumination with 665 nm light for a total dose of 48 J/cm2). Tumors are treated with an immune-enhancing PDT regimen followed by a tumor-controlling PDT regimen that can leads to enhancement of anti-tumor immunity while retaining effective control of primary tumor growth. Following illumination, mice are rested for 9 days; on a ninth day, mice are injected with HPPH. On day 10 following the first treatment, tumors are treated with a tumor control treatment regimen (illumination with 665 nm light for a total dose of 132 J/cm2 given) [2].