An immunosensor is described that is based on fluorescently labeled F(ab') anti-human serum albumin antibody fragments covalently immobilized to the distal end of a fiber-optic probe. When human serum albumin is present, it is bound to the sensor and shields the fluorescent label from the solvent water, and a significant increase in the label fluorescence results. The sensor can be regenerated by simply immersing the sensing tip in chaotropic media. Under these conditions the antigen-antibody complex is selectively disrupted without adversely affecting the sensor. In the present configuration, the same sensor can be recycled over 50 times before the immunosurface inactivates significantly. With proper storage the sensor can last for up to 4 months.
We describe and characterize a new instrument for the measurement of: (1) steady-state excitation, emission, and absorbance spectra; (2) fluorescence lifetimes; and (3) phase-resolved fluorescence spectra in supercritical fluid media. Time resolution is on the order 10–20 ps, spectral resolution is 1 nm from 225–700 nm, and pressure and temperature can be controlled accurately and safely from 1 to 300 ± 0.7 atm and 273.2 to 373.2 ± 0.1 K, respectively. The instrument shows great promise for the elucidation of complex solvation processes occurring in supercritical fluid media.
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