Spectral characterization of the benzoporphyrin derivative monoacid ring-A photoproduct formed in fetal calf solutions during irradiation with 694 nm continuous-wave radiation.
Benzoporphyrin derivative monoacid ring A (BPD-MA) is a second-generation photosensitizer for photodynamic therapy (PDT) that has shown good results in phase I clinical trials. Similar to other porphyrin derivatives, BPD-MA readily photobleaches during in-vivo PDT treatment. This study investigated the photodegradation of BPD-MA in fetal calf serum (FCS) solutions in vitro. Absorption and fluorescence spectra from dilute solutions of BPD-MA in 10% FCS were recorded before and immediately after irradiation with light at 694 nm. After irradiation, the appearance of a new fluorescence emission band at 650 nm and changes in the fluorescence excitation spectra indicate the formation of a photoproduct. Photoproduct formation was observed only when BPD-MA was bound to FCS and in oxygenated solutions. The spectroscopy of the photoproduct is consistent with the reaction of an oxygen species with the ring B vinyl group, forming a hydroxyaldehyde photoproduct. Monitoring the increase in photoproduct fluorescence during treatment may provide an in-vivo dosimeter to measure PDT efficacy.
Gillies
R
R
Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston, USA.
Kollias
N
N
Hasan
T
T
Diddens
H
H
D000818:Animals; D002417:Cattle; D006801:Humans; D007834:Lasers; D010777:Photochemistry; D010778:Photochemotherapy; D011166:Porphyrins / Q000737:chemistry* / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents / Q000737:chemistry* / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014407:Tumor Cells, Cultured
D011166:Porphyrins; D011838:Radiation-Sensitizing Agents; C504224:benzoporphyrin D