Bioeffect Of Laser

With the development of laser technology, the bio-application of laser has made great progress in many fields.Laser irradiation therapy, especially intravascular low level laser (ILLLI) therapy has been applied in clinic for a long time and has been proved to be an effective method to various diseases. However, its mechanism still remains unclear. In this dissertation, animal test and spectrum analysis were employed to investigate the mechanism of ILLLI therapy. A viewpoint that laser irradiation can improve the capability of blood carrying oxygen was brought forward based on the results.The invention of optical tweezers is another important achievement. Because it can be used to manipulate living biological specimens without physical contact and invasion, the technology and applications attract more and more physicists and biologists' attentions. In this dissertation, the optical tweezers system, its key techniques and biological applications have been studied in detail.On construction of optical tweezers, a dual-optical tweezers system was set up using a Ti-Sapphire laser. The optical trap steering and sample micro-manipulation systems were constructed. The displacement and force measurement systems were incorporated, and displacements of nanometers and forces of picnewtons can be detected. The influence of illumination conditions on the detector and temperature in sample cell was investigated. And a method of calibrating laser trap stiffness using Brownian motion in the condition of low sampling frequency was studied. Furthermore, in order to study the mechanisms of polymerizaton and depolymerization of tubulin under different conditions such as PH, temperature, and biological factor, a flow sample cell with temperature-control system was designed and fabricated.In applications of optical tweezers, red blood cells, yeasts, coliforms, phagocytes, chloroplast, etc. were successfully manipulated. In force measurements, the static and dynamic tether forces of leukemia cell and mammary cancer cell membranes weredetected. The tether forces of mammary cancer membranes in different conditions were compared. And the mechanical properties in the process of tether formation were discussed. In the experiment of microtubule, the mechanics of depolymerization of tubulin after treatment is being studied using this system, and a phenomenon of microtubule breaking after being irradiated by exciting light was studied in detail.