Colloidal properties and protein adsorption of amphoteric microspheres

Polymer microspheres prepared with the soap-free emulsion polymerization in the presence of amphoteric azo-initiators exhibited amphoteric behavior that depended upon the pH. The residual density of initiator fragments at particle surfaces, the electrophoretic mobility and critical flocculation concentration of colloidal microspheres were determined. It was found that the behavior of pH dependences of the colloidal properties corresponded well with the dissociation behavior of amphoteric initiators, i.e. amphoteric initiator fragments at the surfaces. In addition, the adsorption behavior of two proteins onto amphoteric particles was investigated. The effects of pH and ionic strength on protein adsorption onto the microspheres were emphatically examined.