Gold nanoparticles functionalized with Pluronic are viable optical probes for the determination of uric acid

The authors describe the preparation of gold nanoparticles (AuNPs) coated with poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic F-108) by reducing Au³⁺ to Au⁰ using curcumin, a natural and non-toxic food spice, in water of pH ~7 in the presence of F-108 and Ag⁺ ion. The coated AuNPs display strong resonance Rayleigh scattering (RRS) and fluorescence that results from the functionalization of the gold surface with curcumin and Pluronic F-108. The molar mass of Pluronic F-108 affects the particle size of the AuNPs formed, and small AuNPs are formed when using low molar weight F-108 that was purified by centrifugation or dialysis. The coated AuNPs were employed in an optical method for the determination of uric acid. The combination of uric acid with the AuNPs boosts both the RRS signal and the fluorescence of the AuNPs. However, higher concentrations of uric acid shift the fluorescence peak to shorter wavelengths. The method is simple, and fluorescence, best measured at excitation/emission wavelengths of 425/534 nm, increases linearly in the 50 μM to 50 mM uric acid concentration range, with a 0.14 μM detection limit which is lower than reported for other methods in the literature. Graphical abstract Pluronic F-108 capped gold nanoparticles prepared by reducing Au³⁺ to Au⁰ using curcumin can estimate uric acid in 50 μM to 50 mM concentration range.