Fiber-Optic Immunosensor Based on an Etched SMS Structure

A novel and high sensitive IgG - anti-IgG biosensor based on multimode interference induced through a single-modemultimode-single-mode (SMS) optical fiber structure is developed in this contribution. First, an improvement of the performance of a basic 125-mu m-diameter SMS structure is carried out by etching the optical waveguide cladding to a diameter of 15 mu m. This leads to sensitivity values eight times higher than the original SMS structure. Then, 3-glycidopropyl-trimethoxysilane is used to attach the IgGs to the optical substrate. Finally, a phosphate buffer saline solution containing an increasing concentration of antigoat IgGs is used to detect biological interactions up to 104 mu g/ml. High-resolution mass spectrometry was used to corroborate the attachment of the biomolecules to the optic fiber. The analyzed bioprobe presents no cross sensitivity to other biomolecules immersed in the same detection solution.