<title>Liquid chromatography combined with visible diode-laser-induced fluorescence detection for photosensitizers</title>

Abstract

A combination of conventional-size liquid chromatography and visible diode-laser induced fluorescence (DIO-L]F) detection has been developed and applied for the detection of a model photosensitizer, AJPcS2, in biological samples. Conventional fluorimetry was found to give unsatisfactory information. A detection limit of 2.1x1012 M (SIN = 3) was obtained for A1PcS2 in both rat urine and faeces exiracts using the DIO-LIF system, 20-fold lower than obtained with a conventional fluorescence detection system, when used in combination with chromatography. . INTRODUCTIONPhotodynamic therapy (PDT) is a treatment for neoplastic diseases based on selective cell injury. A photosensitizer is administered and after a certain period of time the tumor tissue is irradiated, what results in tumor necrosis [1]• Tumor destruction is thought to be based on the photochemical formation of cytotoxic oxygen species as a result of energy transfer from excited photosensitizers. Photosensitizers should show selective or prolonged retention in tumor tissue compared to nonnal tissue and afterwards be easily cleared from all tissues. Furthennore, they should have appropriate photophysical characteristics, be chemically and photochemically stable and non-toxic in the absence of light [2]• Their absorption maximum should preferably be at a long wavelength, where tissue transparency is high.The most widely used photosensitizer for PDT is Hematoporphyrin Derivative (HpD), a complex mixture of structurally related dicarboxylic porphyrins. In PDT, HpD is activated at a wavelength of 630 nm because tissue penetration is too low at 400 run, the maximum absorption band of the porphyrins present in HpD. A more suitable photosensitizer would have a better defined composition and a maximum absorption wavelength longer than 650 nm [1] A number of new photosensitizers has been developed with this requirement in mind [31141• We have developed a separation and detection system for so-called second generation photosensitizers and applied it to a model compound: disulfonated aluminum phthalocyanme (AIPcS2). The absorption maximum of this phthalocyanine is at a wavelength of 674 nm in methanol (E = 180,000 cm M1).It is well known that the number of sulfonate groups on the phthalocyanine is a major factor in the uptake and the disthbution of a mixture of AIPcSn (n = 1-4 sulfonate groups) in tumor cells [5] [6J• AJPcS2 can be obtained as a preparative chromatographic fraction from such an AIPcSn mixture [7]• However, several A1PcS2 isomers are possible and the isomeric SO3H distribution in the AIPcS2 fraction depends on the method of synthesis applied for the AIPcSn mixture [8][9][lO]• It is N expected that AIPcS2 isomers with sulfonates on adjacent rings are more lipophiic than those with sulfonates on opposite rings [1O]• Figure 1: Structure of a A1PcS2-isomer O-8194-1351-8/94/$6.OO SPIE Vol. 2084 1255 N Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx