The single mode tapered optical fibre loop immunosensor: II. Assay of anti-cholera toxin immunoglobulins

An evanescent wave immunoassay for cholera antitoxin immunoglobulins was performed using a single mode tapered optical fibre loop sensor. The transducer was silanised with 3-glycidoxypropyltrimethoxysilane and chemically modified to link covalently either cholera toxin B subunit or a synthetic peptide derived from it, CTP3. The sensor was exposed to semI fluids, obtained from human volunteers having been exposed to live virulent Vibrio cholerae 01 and shown to produce rice-water stools. Other toxins of interest, such as Clostridium botulinum toxin A, have been tested on similar systems [19]. The bound unlabelled immunoglobulins were then exposed to a mixture of FJTC-anti-IgG and TRITC-anti-IgA, without requirement for a separation step. The emanating fluorescent emissions of fluorescein and rhodamine, excited by the input laser light, were coupled back into the guided mode of the tapered fibre, and used to determine the concentrations of the complementary antigens.