The effects of laser irradiation with 632.8 and 532 nm on rheological properties of blood were comparatively studied in vitro. Under the irradiation condition of 30 mW, laser irradiation of blood samples using a spot diameter of 5 mm with each laser, showed promising results in the modulation of hemorheological properties. When blood samples from patients with abnormally high values of erythrocyte sedimentation rate (ESR) were irradiated, the values of ESR were lowered statistically by either of the 632.8 or 532 nm lasers. The laser irradiation reduced blood viscosities at different shear rates (10-110 S-1) for the hyper-viscosity blood samples. Laser irradiation increased the electrophoretic mobility (EPM) of erythrocytes when the values of the sample's EPM were abnormally slow. The erythrocyte deformability was enhanced by laser irradiation when the deformability of the sample from the patients was originally poor. For verifying the improvement of laser irradiation on erythrocyte deformability, the typical erythrocyte samples with poor deformability were produced by the pre-treatment of the erythrocytes with Ca2+. The deformability of these erythrocyte samples was also improved after laser irradiation. These results suggest that membrane-bound hemoglobin (Hbm) might be the initial site of the interaction, since Hbm is the main cause of poor deformability when erythrocytes were treated with Ca2+. In all experiments including ESR, blood viscosity, EPM and erythrocyte deformability, the 532 nm laser demonstrated more efficient effects on modulating rheological properties than 632.8 nm laser. This wavelength effect is consistent with the absorption spectrum of hemoglobin, reflecting that hemoglobin may be one of the action targets under laser irradiation. (C) 2004 Elsevier B.V. All rights reserved.
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