Interaction of low level laser radiation with biological systems

Recently has appeared different articles that reported the use of microwaves and laser radiation to modify the behavior of biological systems. Laser radiation has been applied to stimulate the growth of E. Coli cultures, the DNA replication and division, the activation of some genes and the activation of the growth of some seeds between others. It is important to mention that each biological system requires different parameters of radiation for stimulation. There are three factors that are determinant to obtain an early response in a biological system; these parameters are the wavelength (nm), the intensity (W/m
²
) and the dose (J/m
²
). The wavelength determines the penetration of laser radiation into tissues while the intensity and the dose determine the stimulation effect and its magnitude. From the above mentioned if appropriate parameters of laser radiation are applied, activation of the biological system can occur. The present work investigated the behavior of three different biological systems when they were irradiated with different laser wavelengths. The three biological systems studied were cucumber seeds (Cucuminus sativus L), wheat seeds (Triticum aestivum L) and human fibroblasts. The cucumber seeds were irradiated with a laser wavelength λ=650 nm. The intensities of laser radiation were 2.5 mW/cm
²
, 5 mW/cm
²
, 10 mW/cm
²
and 20 mW/cm
²
and the exposition times were 60s, 120s and 300s.