Phototransformations of 5-aminolevulinic acid-induced protoporphyrin IX invitro: A spectroscopic study

Human adenocarcinoma cells of the line WiDr were incubated with 5-aminolevu linic acid to induce protoporphyrin yi (PpIX) and then exposed to laser lig ht of wavelength 635 nm, The PpIX fluorescence decreased with increasing ex posure, The decay rate was slightly dependent on the initial PpIX concentra tion, The PpIX fluorescence was halved by a fluence of about 40 J/cm(2), Se veral fluorescing photoproducts were formed, The main one, supposedly the c hlorin-type photoprotoporphyrin (Ppp), had a fluorescence excitation spectr um stretching out to about 680 nm with a maximum at around 668 nm, The form ation kinetics of this product was dependent on the initial PpIX concentrat ion. Moreover, it was selectively bleached by exposure to light at 670 nm, A photoproduct with an emission maximum at 652 nm, different from Ppp, rema ined after this exposure. Traces of a photoproduct(s) with fluorescence emi ssion slightly blueshifted compared with that of PpIX, supposedly water-sol uble porphyrins, were also detected after light exposure.