Fluorescent optrode for proteins based on a diketopyrrolopyrrole
derivative: practical application to total protein determination in
urine
Abstract
A fluorescent sensor based on a diketopyrrolopyrrole (DPP) derivative
for protein detection was designed and tested in urine samples. The DPP
derivative emits visible light as a solid, making this molecule
particularly appealing as a recognition molecule for a sensing optical
fibre. In the presence of proteins, the sensor displayed a fluorescence
enhancement. The sensor linear dynamic range for protein ranges from 10
mg L-1 to 100 mg L-1. Detection limit (LOD) of this fluorescent optrode
was better than the one of the classical spectrophotometric Biuret
method and similar to the LOD of the spectrophotometric Ponceau-S/TCA
method. Economy of reagents and time is a clear advantage of the
analytical method based on the optrode we are now proposing, regarding
the Ponceau-S/TCA, thanks to the reversibility of recognition layer, and
to the needleless of treating the standards with trichloroacetic acid,
and consequently of centrifuging them. Besides, the most common
interferences in protein determination by classical spectrophotometric
methods, like sodium dodecyl sulfate, acetone, and glucose, do not
affect the optrode response, neither does fluoride ion. The new
fluorescent optrode was tested in the determination of total proteins in
urine from healthy individuals (low concentrations). Results were not
statistically different from the ones obtained with the Ponceau-S/TCA
spectrophotometric method.