Pyrophosphate functionalized silver nanoparticles for colorimetric determination of deferiprone via competitive binding to Fe(III)

The authors describe a colorimetric assay for the determination of the iron chelating drug deferiprone by using water dispersible silver nanoparticles functionalized with pyrophosphate groups (Pyro-AgNPs). The pyro-AgNPs are capable of cooperatively binding Fe 3+ ions, and this results in a color change from yellow (peaking at 402 nm) to red (peaking at 520 nm) due to aggregation. However, this binding is competitively overruled, and hence aggregation is prevented in the presence of increasing concentrations of deferiprone. Consequently, the color (which is due to localized surface plasmon resonance) gradually changes from red to yellow, and this can be correlated to the concentration of the drug. The relative amounts of silver nanodispersion and pyrophosphate anions, of the pH values of the medium, and reaction times were optimized. Under the best conditions, the method exhibits a consistent optical response in the 6.0 to 100 μM deferiprone concentration range, with a 280 nM detection limit. The assay is selective over several amino acids, saccharides, and inorganic ions. The method was applied to the determination of deferiprone in pharmaceuticals and in spiked human plasma samples. Graphical abstract Schematic of the colorimetric deferiprone assay using pyrophosphate functionalized silver nanoparticles via competitive binding to Fe(III) ions. The probe was used to determine deferiprone in pharmaceuticals and human plasma.