IN-VIVO PHOTODYNAMIC THERAPY WITH THE NEW NEAR-IR ABSORBING WATER-SOLUBLE PHOTOSENSITIZER LUTETIUM TEXAPHYRIN AND A HIGH-INTENSITY PULSED-LIGHT DELIVERY SYSTEM

An in vivo fluorescence monitoring and photodynamic therapy (PDT) stud y was performed using the new photosensitizer lutetium texaphyrin (Lu- Tex). This photosensitizer is water soluble and has the additional adv antage of strong absorption near 730 nm. C26 colon carcinoma was trans planted in the foot of BALB/c mice. In vivo fluorescence spectroscopy was applied to study Lu-Tex tissue distribution kinetics. For this pur pose, fluorescence intensity both in the foot with the tumor and in th e normal foot was measured in vivo by the laser-induced fluorescence ( LIF) system. For PDT, both feet of the mice were irradiated simultaneo usly with the use of a new high intensity pulsed light delivery system , the Photodyne. The results of the LIF measurements showed that the m aximal fluorescence intensity ratio between the normal and tumor beari ng foot (FIR) was observed 24-48 h after the agent injection. Photoirr adiation with doses from 90 to 240 J cm(-2) (0.6 J cm(-2) per 2 ms pul se, 1 Hz) 24 h after injection of Lu-Tex at a dose of 10 mg kg(-1) cau sed significant tumor necrosis and delay in the tumor growth rate. The antitumor effect was enhanced with increasing light doses. Normal tis sue response to PDT with Lu-Tex was determined as the damage index of the normal foot, which was irradiated simultaneously with the tumor be aring foot, The normal tissue response after PDT with Lu-Tex was compa red with 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PP), c hlorin ed (Chi) and Photofrin (PII) at the same values of antitumor ef fect. The results showed that at 50, 80 and 100% inhibition of tumor g rowth the orders of the values of normal foot damage indexes were as f ollows: ALA > Lu-Tex greater than or equal to PII > Chi, PII > ALA > L u-Tex > Chi and PII > Lu-Tex > ALA > Chl respectively. (C) Elsevier Sc ience S.A.