Light-Scattering Characteristics of Biological Particles

Abstract

Measurements have been obtained of the light-scattering characteristics of 0.5 μ diameter polystyrene spheres, red blood cells, and hemoglobin free red cell “ghosts.” The information obtained consists of measurements of the magnitude of laser radiation scattered by dilute aqueous suspensions of the above particles as a function of the particle concentration and the angle of observation, measured from the direction of the incident beam. In addition, the results for the spheres are compared to analytical predictions calculated from the Mie theory.

The light source employed is a 75 mW He Ne laser operating continuously at 632.8 nm. The laser beam is spatially filtered and focused (large F no.) at the center of a 1.6 cm i.d. cylindrical glass scattering cell. Scattered intensity measurements are obtained with an S-20 multiplier phototube, mounted on a beam which rotates about the scattering cell as an axis.

The data for the polystyrene spheres are quite strongly forward directed with a relative minimum at about 70° and a secondary maximum at about 100°, in good agreement with the Mie theory prediction. The scattering distributions for red cells and ghosts are even more strongly forward directed than for the spheres; however, there are no apparent maxima or minima for either of the latter. Analytical predictions of scattering from red cells or ghosts are not attempted.