The effect of three variables on adsorption of rabbit IgG to colloidal gold

The purpose of this investigation was to (a) begin to evaluate the coagulation curve as a means of selecting the minimal quantity of IgG required to stabilize colloidal gold (Au); (b) determine the effect of the quantity of IgG added, the pH of adsorption, and the isoelectric point (pI) range of the IgG on the quantity of IgG bound and the stability of the IgG-Au complex with respect to desorption; and (c) discuss these results with respect to current theory on the effect of pH on adsorption of IgG to surfaces. No absolute minimal value required to prevent coagulation could be determined despite the high reproducibility of the values obtained; approximate values were selected. Each variable had an effect on the quantity of IgG bound: as the quantity of IgG added increased, the quantity bound increased; as the pH of adsorption became more alkaline, the quantity bound decreased; and as the pI range of the IgG became more alkaline, the quantity bound increased. IgG-Au complexes with a variable number of bound IgG molecules, depending on the three variables selected, can be produced. Production of IgG-Au composed of uniform numbers of IgG is discussed. A modification of the current theory on the effect of pH on adsorption of IgG is proposed.