[Computer-controlled laser irradiation unit for studies of light-induced processes in cell cultures]

For the photodynamic treatment of tumours, synergistic effects of photosensitizing substances and light (today usually laser light) are used. With the aim of optimizing photosensitizing drugs and therapy, the effects of light and drug dose were studied in cell experiments. To automate and standardize such in vitro experiments, a laser irradiation chamber was developed. Cells cultured from tumour cell lines are placed on micro-titre plates or in petri dishes, together with the photosensitizer, 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 irradiated from below. In this way, light dose errors due to refraction from the meniscus of the cell suspension as occurs with irradiation from above, are avoided. During irradiation, speckle effects on the underside 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.