Development Of A Fiber Optic Biomolecular Probe Instrument Using Near-Infrared Dyes And Semiconductor-Laser Diodes

The development of a near-infrared fiber optic biomolecular probe (FOBP) for the detection of biological molecules will be discussed. The utility of the system is demonstrated using an immunochemical samples. The FOBP consists of a semiconductor laser diode (lambda(max) = 780 nm), a modified fiber tip binding site, an NIR dye and a detector. The common distal end of two optical plastic fibers, connected with poly(methyl methacrylate), serves as the binding site (about < 2mm(x) in diameter). Activation of the binding site with different inorganic acids is discussed. Preparation of the FOBP involved in the immobilization anti-IgG antibody followed by coating with IgG for a sandwich type probe. Immobilization of anti-IgG antibody was achieved by reacting the Fc fragment of the antibody molecule to the activated binding site of the fiber. The instrument was tested by labeling the antibody with a commercially available near infrared (NIR) dye IR-144). Excitation of the antigen-antibody sandwich complex was induced with a semiconductor laser diode at 780 nm. The emission intensity signal was collected at 820 nm by using small bandwidth filters. The response time for 95% of the signal was less than 5 seconds. The low background signal of the detector allowed the detection of 2.72 ng/ml IgG in a probe coated with 10 ng/ml antibody. The general procedure used for the attachment of the biological molecule to the distal end of the probe can be used to construct more specific antigen-antibody systems. Use of smaller components shown here will allow for the manufacturing of portable instruments for applications in medicine and clinical analysis.