Methotrexate as a photosensitiser.

The absorption, excitation and emission spectra of methotrexate (MTX) solutions in natural saline water and sodium hydroxide at 10(-4)-10(-5) MpH=8.4 were measured, while they were exposed to coherent and uncoherent visible and near ultraviolet (UV) light. Xe and Hg lamp and also a nitrogen pulsed laser radiation were used. The absorption spectra exhibited spectral bands between 225 nm and 450 nm. The 200 nm - 500 nm excitation spectra were measured with emission centred on 470 nm; fluorescence excitation was observed at 340 nm and 370 nm; emission fluorescence was detected between 400 nm and 600 nm, showing a maximum at 470 nm. Spectra modifications, non-linearly depending on exposure time (varying from 3 min to 180 min), indicated the photodissociation of MTX to the fluorescent compound 2,4 diamino-formylpteridine. In a preliminary in vivo experiment, rapid destruction of neovascularisation was observed in the MTX-impregnated conjunctive of the rabbit eye exposed to uncoherent UV and visible light.