Development of an “Electroptode” Immunosensor:  Indium Tin Oxide-Coated Optical Fiber Tips Conjugated with an Electropolymerized Thin Film with Conjugated Cholera Toxin B Subunit

Abstract

We demonstrate that it is possible to create surface-conductive fiber optics, upon which may be electropolymerized a biotinylated polypyrrole thin film, which may then be used to affinity coat the fiber with molecular recognition probes. This fiber-optic electroconductive surface modification is done by the deposition of a thin layer of indium tin oxide. Thereafter, biotin-pyrrole monomers are electropolymerized onto the conductive metal oxide surface and then exposed to avidin. Avidin-biotin interactions were used to modify the fiber optics with biotin-conjugated cholera toxin B subunit molecules, for the construction of an immunosensor to detect cholera antitoxin antibodies. The biosensor was tested for sensitivity, nonspecificity, and overall practicality.

Preparation of Nanostructured Film Arrays for Transmission Localized Surface Plasmon Sensing

“…Preparation of various nanoisland films using different metal nanoparticles such as Ag, Cu, and Pd nanoparticles can also be attempted. In addition, an ability to coat curved or enveloped surfaces with metal nanoisland arrays using our self-assembly/ thermolysis approach can be another potentially important advancement in fiber optics [64,65].…”

Immobilization of Biomolecules by Electropolymerized Films

“…[47][48][49] The binding of compact and active biological macromolecules was thus achieved using avidin-biotin interactions between biotinylated polypyrroles and biotinylated enzymes, antibodies, oligonucleotides, and even biotinylated bacteria. 25,[50][51][52] In contrast to the linear structure of biotinylated polypyrrole films, the synthesis of biotin derivatives bearing several electropolymerizable units allowed the emergence of biotinylated films with a cross-linked skeleton. For instance, the electropolymerization of a chiral biotin substituted by two carbazole groups led to a cross-linked film exhibiting stereoselective properties toward the permeation of chiral compounds.…”

A strategy for signal amplification using an amperometric enzyme immunosensor based on HRP modified platinum nanoparticles

“…The aim of this study is to develop a sensitive electrochemical enzyme immunosensor with an amplified signal by using a combination of HRP-Pt nanoparticle hybrid systems and avidin-biotin interactions. The avidin-biotin immobilization technique offers various advantages over other immobilization techniques such as (a) avidin has four binding sites for biotin per avidin molecule [13], and the extremely specific and high affinity interaction of avidin-biotin [14] leads to strong associations similar to the formation of a covalent bond [15]; (b) avidin provides a passivation layer over the substrate surface, which subsequently helps prevent nonspecific adsorption of biomolecules to the surface; (c) the avidin-coated substrate can be homogeneously linked with biotinylated antibodies, antigen, or enzymes; (d) the avidin-biotin-based immobilization method can be carried out under very mild conditions and maintains the biological activity of the immobilized biomolecules more successfully than other commonly used methods [16]. These advantages prompted us to prepare novel avidin-labeled HRP-functionalized PtNPs.…”