COMPUTER-ASSISTED LASER IRRADIATION UNIT FOR THE INVESTIGATION OF LIGHT-INDUCED PROCESSES IN CELL-CULTURES

For the photodynamic treatment of tumours, synergistic effects of phot osensitizing substances and light (today usually laser light) are used . With the aim of optimizing photosensitizing drugs and therapy, the e ffects of light and drug dose were studied in cell experiments. To aut omate and standardize such in vitro experiments, a laser irradiation c hamber was developed. Cells cultured from tumour cell lines are placed on micro-titre plates or in petri dishes, together with the photosens itizer, and subsequently irradiated in the irradiation chamber with a well-defined dose of laser light of a wavelength corresponding to the absorbance of the photosensitizing agent. The plates or dishes are irr adiated from below. In this way, light dose errors due to refraction f rom the meniscus of the cell suspension as occurs with irradiation fro m above, are avoided. During irradiation, speckle effects on the under side of the plates or petri dishes lead to variation in irradiation. A vibrator keeps the light transmission fibre and thus speckle pattern in motion, guaranteeing a homogeneous irradiation of the cells.