Aggregation rate measurements by zero-angle time-resolved multiangle laser light scattering

Abstract

A new method for determining second-order aggregation rate constants via time-resolved multiangle laser light scattering is introduced. A major advantage of this approach is that second-order aggregation rate constants are determined without any assumptions regarding the dimer intraparticle interference or form factor. The second-order aggregation rate constants are calculated from the temporal variation of the zero-angle excess Rayleigh ratio within the context of von Smoluchowski's well-established model of colloidal aggregation. The new method is illustrated with two systems: (1) GM1-bearing liposomes aggregated in the presence of the cholera toxin B subunit and (2) sulfonated polystyrene latex aggregated in the presence of CaCl2. Whereas the method is demonstrated to be particularly well-suited for investigating slow aggregation processes, rapid aggregation processes are also accessible if proper precautions are taken.