SIZE AND CHARGE-DISTRIBUTIONS OF RADIOCOLLOID PARTICLES

We describe a new method to determine the size and charge distributions of radiocolloid particles. The method combines band electrophoresis in a stabilizing sucrose density gradient with light scattering intensity measurement of the relative particle concentration at each point in the gradient. Quasi-elastic laser light scattering is then used to determine the translational diffusion coefficients, and thus the hydrodynamic radii of the colloidal particles, which are assumed to be spherical. Determination of the electrophoretic mobility and radius enables calculation of the particle charge and surface charge density. The heterogeneity of electgophoretic mobility in the particle population causes the initially narrow band to spread out, so that size and charge distributions can be determined. We have applied the technique to 2 radiocolloids commonly used in nuclear medicine: human serum albumin minispheres and 99mTc-sulfur colloid. Agreement with sizes previously determined by other methods is reasonable. © 1979.