Modeling reaction-transport processes in a microcapillary biosensor for detection of human IgG

Mathematical modeling of electrokinetic transport processes and antigen-antibody interactions in a microfluidic biosensor for heterogeneous immunoassay is described. Two mathematical models of externally controlled electroosmotic transport are constructed - the slip model based on Helmholtz-Smoluchowski approximation and the non-slip model based on the use of Poisson equation. It was found that the use of the slip model is restricted by concentration of the carrier electrolyte and dimensions of the system. The antigen-antibody interaction cannot be described by the slip model. Dynamics of the heterogeneous immunoassay in the proposed biosensor was also studied. Human-IgG-Protein A was used as model system. Parametric studies revealed strong sensitivity of the biosensor to the antibody charge number and to the character of surface heterogeneity in the position of immobilized antigen. This sensitivity can be one of the reasons why the practical applications of heterogeneous protein chips are still rare. (c) 2006 Elsevier B.V. All rights reserved.