In vitro and in vivo activation of hypericin with the incoherent light source PDT 1200 SOA (520-750 nm) and with solar simulated radiation (290-2500 nm)

The photodynamic active plant pigment hypericin is a possible new photosensitizer for photodynamic therapy. Hypericin shows absorption maxima in the ultraviolet (330 nm) and visible light range (550 and 588 nm). The present study compared the photoactivation of hypericin with the incoherent light source PDT 1200 SOA (520-750 nm) to that with a 1000 watt solar simulator (290-2500 nm). Hypericin displayed dose and time dependent phototoxic effects in the keratinocyte cell line HaCaT in vitro and after intracutaneous in vivo application with both light sources. In vivo, delayed (48 h) photosensitivity in hypericin-sensitized skin was observed. With intracutaneous application of 100 ng/ml hypericin, no phototoxic reaction could be produced. The PDT 1300 SOA was about four times more effective in vitro and about ten times more effective in vivo when compared to the solar simulator. Since the PDT 1200 SOA allows homogenous irradiation of large areas, we conclude that the PDT 1200 SOA is an effective and convenient light source for in vitro and in vivo studies using hypericin.