SCATTERING IN PLANAR SURFACE WAVE-GUIDE IMMUNOSENSORS

Ths signals obtained in a fluorescent sandwich immunoassay for human chorionic gonadotrophin, excited evanescently on an indium phosphate monomode surface waveguide, are analysed in terms of their fluorescent and scattering components. A waveguide surface-scattering theory is applied to these results, enabling a strategy of immunosensor optimization to be developed. A reduced sensitivity is found if 2 min transient responses are used instead of equilibrium-state responses. It is suggested that this reduction arises from the presence of a variable-scattering component in the early stage of the kinetics as a humectant layer dissolves.