Evanescent wave long period fiber Bragg grating as an immobilized antibodybiosensor

An immunosensor using a long-period grating (LPG) was used for sensitive de tection of antibody-antigen reactions. Goat anti-human IgG (antibody) was i mmobilized on the surface of the LPG, and detection of specific antibody-an tigen binding was investigated. This sensor operates using total internal r eflection where an evanescent held interacts with bound antibody immobilize d over the grating region. The reaction between antibody and antigen altere d the LPG transmission spectrum and was monitored in real time as a change in refractive index, thereby eliminating the need for labeling antigen mole cules. Human IgG binding was observed to be concentration dependent over a range of 2-100 mu g mL(-1), and equilibrium bound antigen levels could be a ttained in similar to 5 min using an initial rate determination. Binding sp ecificity was confirmed using human interleukin-2 and bovine serum albumin as controls, and nonspecific adsorption of proteins did not significantly i nterfere with detection of binding. Antigen detection in a heterogeneous pr otein mixture and in crude cell lysate from Escherichia coli was also confi rmed, Moreover, regeneration of the LPG surface via diethlyamine treatment resulted in similar to 80% removal of bound antigen. Subsequently, fibers r eexposed to antigen retained greater than 85% of the initial signal after f ive consecutive regeneration cycles.