Influence of surface chemistry on particle-particle aggregation as measured by a Coulter Counter in the low concentration regime

Abstract

The link between particle concentration, surface properties, and particle aggregation has been investigated for polystyrene latex in the low particle concentration regime, volume fractions less than 1 × 10-6. The particles used in this model study were 9.14-μm diameter polystyrene beads, approximately the same size as red blood cells, using a Coulter Counter with a 100-μm aperture as a gauge of clustering. The lower concentrations of beads displayed the same trend as reported in other publications. Albumin and fibrinogen were then attached to the beads and the effect of non-specific binding by the proteins on particle agglomeration was studied. Albumin showed little effect on the number of aggregates encountered whereas fibrinogen increased the number of aggregates, indicating that stronger particle interactions occurred between the fibrinogen coated particles. The addition of stearic acid had no marked effect on the aggregation properties of the beads, coated or uncoated. The addition of sodium stearate, however, increased the number of doublets, triplets, and multiplets formed. These results may be relevant to adhesion of cells. Our approach is a plausible way to consider the roles that proteins and fatty acid molecules have on the relative binding potential without the constraints of using live cells.