The driving force behind the complex system of metabolism is based on the efficient use of potential differences. An intact biological system has a dynamic equilibrium in which the cellular biochemical reactions are in a pseudo-stationary state. The equilibrium can be manipulated by external effects such as, temperature changes brought about radiation absorption. Hot spots can be induced by the absorption of photons in strongly absorbing areas within the tissue or the sub-cellular components. Simulation calculations were carried out and utilized for selective manipulation within a spatially limited target volume, using simplified parameters for observation of the model. A good correlation was established between the results of the simulation and the measuring data based on absorption and scattering values for fibroblasts and liver tissue. Relevant biochemical causes of the stimulation effects at cellular level are considered in the discussion. The effect of stimulation with a laser on tissue such as cartilage, using a simplified two-dimensional tissue model system which is mainly supplied by diffusion processes, is discussed here with a view to its use in medicine.

The course of arthrosis was investigated on an animal-experimental arthrosis model considering macroscopic aspects, and the proteoglycan and the glycosaminoglycan contents. Based on these parameters, the influence of a low-power diode laser of 692.6nm wavelength on the progress of arthrosis was investigated. Thirty days following joint instability surgery another operation was made during which the femoral condyles were irradiated using different energy densities. Seven days after the second operation, macroscopic findings were made and the proteoglycan content was established based on the quantitative determination according to Taylor and Jeffre. This method is based on various spectrophotometric absorption behaviours of different concentrations of sulphatized glycosaminoglycans in the presence of dimethylmethylene blue.

The influence of laser radiation on human osteoarthrotically changed chondrocytes was investigated using various wavelengths, power density and dependence on the exposure time in order to confirm the positive results obtained in an animal experiment. It was manifested that, if there was a specific parameter constellation (2W; 16W/cm2; 60s; 120J), an enhanced matrix synthesis (cartilage material from 36 patients) could be achieved. The proof succeeded by applying the radioisotope marking method (3H-proline).

A new type of applicator for interstitial laser coagulation is proposed in this paper. The new fiber optic applicator is made by removing the original fiber cladding and replacing it with a sol-gel coating. The sol-gel coating was prepared from the silicate precursor TEOS (tetraethylorthosilicate), mixed with ethanol in acid, which catalyzes hydrolysis. The material is produced with the factor R = 20, where R denotes the number of solvent moles to the number of TEOS moles. In these studies, optical fibers were used from Laser Components (core diameter 400 µm, HCS, low OH). The external jacket was mechanically removed, leaving a remaining 2-cm length of bare fiber. The modified dip-coating method was used to cover the bare fibers with sol-gel material. Two types of applicators were produced: pure sol-gel coated devices and applicators with sol-gel coating doped with photosensitive dyes. The photodynamic activity of chlorophyll-based Photolon and Protoporphyrin IX (PPIX) incorporated within the sol-gels was studied spectrophotometrically. It was demonstrated that sol-gel applicators are capable of performing laser interstitial coagulation using a semiconductor cw laser at 980 nm. It was also demonstrated that the incorporated photosensibilizers retain their photochemical activity.