Point-of-care biosensors for uric acid based on target-induced changes in the photothermal effect of gold nanostars using a thermometer as a readout device

Abstract

To meet the requirements of point-of-care testing (POCT), the development of miniaturized and user-friendly readout strategies has become increasingly valuable and significant. Gold nanostars (AuNSs) have a stronger photothermal effect than spherical gold nanoparticles due to the multiple pointed protrusions on their surface. In this study, a simple POCT biosensor for uric acid (UA, chosen as a model target) was developed based on the photothermal effect of AuNSs using a simple thermometer as a readout device. In the presence of urate oxidase (UAO), different amounts of UA react with dissolved oxygen to generate different amounts of H₂O₂. The generated H₂O₂ molecules etch the surface of AuNSs with the help of Fe²⁺, leading to the gradual weakening of the spiky features of the star-shaped nanoparticles until their morphology stabilizes to an approximately spherical shape. The change in the morphology and particle size of AuNSs causes a blue shift of the localized surface plasmon resonance (LSPR) peak, leading to a decrease in the system temperature under laser irradiation. The change in temperature exhibits a linear relationship with the UA concentrations in the range of 5.0–500.0 μM, with a limit of detection (LOD) of 1.6 μM. Through this simple strategy, the detection of UA can be completed within 14 minutes using only a regular thermometer. This method was successfully validated for the detection of UA in serum and urine samples. Since various enzymatic reactions can produce H₂O₂, this proposed method can be adapted to detect different analytes by simply replacing the enzyme used.