K. Taga et al., IN-SITU ATTENUATED TOTAL REFLECTANCE FT-IR ANALYSIS OF AN ENZYME-MODIFIED MIDINFRARED FIBER SURFACE USING CRYSTALLINE BACTERIAL SURFACE-PROTEINS, Analytical chemistry, 66(1), 1994, pp. 35-39
This paper presents a new method for chemically modifying the surface
of a chalcogenide glass optical fiber under permanent control by in si
tu IR-ATR spectroscopy. In order to immobilize glucose oxidase on the
surface of such an IR-transparent wave guide, crystalline bacterial ce
ll surface layers (S-layers) were used as a carrier, instead of using
silanes as an enzyme coupler as frequently described in the literature
. S-layer proteins which have the capability for self-assembling on su
itable surfaces, were cross-linked and further activated with glutaral
dehyde before the immobilization procedure. The reactive enzyme layer
coating the core of the fiber serves to catalyze chemical reactions sp
ecifically when the fiber is used as chemical sensor. The chalcogenide
fiber was coupled to a Fourier transform infrared (FT-IR) spectromete
r which yielded spectra at various stages of the chemical processes as
well as developments of signal bands as a function of time. The fiber
was used as ATR element and could provide evanescent-field IR spectra
in the range of 4000-800 cm-1 of the covering surface film thickness
estimated at approximately 40 nm. All experimental surface modificatio
ns were carried out in situ in a 12-cm-long flow cell into which the f
iber was positioned initially.