Polymer immobilization chemistry for the preparation of fiber optic sensors

A new methodology for preparing fiber optic sensors with covalently attached transduction reagents is described. It is based on the copolymerization of indicator dyes and/or enzymes with hydrogels which are attached to the optical fiber surface. The chemistry is comprised of three fundamental unit operations: (1) surface chemistry to activate the glass fiber tip for inclusion in subsequent bonding chemistry, (2) derivatization or linking chemistry for incorporation of the transducer into multiple sites on the polymer, and (3) polymer chemistry to increase the surface area of the fiber tip and also serve as a support for attachment of sensor reagents.; The pH sensor was prepared by incorporation N-fluoresceinyl acrylamide into an acrylamide-methylenebis(acrylamide) copolymer that was attached covalently to a glass fiber activated for polymerization by either silane treatment or plasma deposition. The sensor exhibited very rapid response times and reversible measurements over the pH range of 4.0-7.5, with indicator properties similar to those of fluorescein. The optimization of the procedure delineated important factors in the sensor preparation, such as the pH of the initial monomer solution, the nature of the polymer initiation, and the concentration of dye.; The CO{dollar}sb2{dollar} sensor required the consecutive application of a CO{dollar}sb2{dollar} permeable membrane over the pH sensing layer, and was accomplished with a siloxane polymer treatment. Sensors were prepared which were based on different combinations of dye/polymer in the pH sensing region, and resulted in CO{dollar}sb2{dollar} sensors with different sensitivities.; The preparation of an enzyme-based penicillin sensor consisted of a polymer support covalently attached to the fiber tip, containing the enzyme penicillinase and a pH-sensitive fluorescent dye. A signal was produced when the enzyme catalyzed the cleavage of the {dollar}beta{dollar}-lactam ring of penicillin to produce penicilloic acid.; A study secondary to the fiber optic sensor preparation is also described, concerning the intramolecular self-quenching of fluoresceinamine. This fluorescein derivative has a quantum yield of 0.015 and exhibits none of fluorescein's indicator properties until the amine's electron lone pair is sequestered through covalent or electrostatic binding processes. (Abstract shortened with permission of author.)...