Uricase biofunctionalized plasmonic sensor featuring Aptes-modified Gold-GQD multilayer film for uric acid detection

Imbalances in uric acid (UA) levels, if neglected, can potentially lead to life￾threatening health issues, underscoring the importance of regular monitoring. However, detecting UA is challenging due to its low concentration and small molecular weight. This study introduces surface plasmon resonance (SPR)-based sensors designed to accurately measure UA levels within relevant physiological ranges, addressing these challenges. The research begins by optimizing gold film thickness and incorporating gold–graphene quantum dots (GQD) into a multilayer film for enhanced precision. Surface functionalization with 3- aminopropyltriethoxysilane (APTES) ensues, forming self-assembled monolayers (SAM) for better adhesion, followed by biofunctionalization with uricase enzyme to improve selectivity. The multilayer film sensor probe significantly outperforms the gold sensor probe, with a higher sensitivity of 3.77%/(mg/dL) versus 0.23%/(mg/dL), a better correlation coefficient (0.825 vs. 0.0318), and a lower limit of detection (LOD) at 4.74 mg/dL compared to 32.85 mg/dL. Surface functionalization increased sensor probe sensitivity by 60.64% with values of 0.0221°/(mg/dL) for the multilayer probe and 0.0355°/(mg/dL) for the surface-functionalized probe. It is accompanied by linear correlation coefficients of 0.8249 and 0.8509, and LODs of 5.16 mg/dL and 0.2 mg/dL, respectively. Biofunctionalization with uricase enzyme increased sensitivity to 0.0755°/(mg/dL), exhibiting a strong linearity coefficient of 0.8313 and a low LOD of 0.095 mg/dL. Notably, the biofunctionalized probe demonstrated exceptional selectivity, showing higher resonance angle shifts for UA— 1.1135° compared to minimal shifts— 0.1853° for interferents like glucose, ascorbic acid, urea, D-cystine, and creatinine, at equivalent concentrations. Overall, incorporating a multilayer film coating and surface functionalization significantly enhances the sensor probe's performance by increasing functional group density and binding site availability. The uricase enzyme further ensures highly specific and selective interactions with UA. These results affirm the developed sensor probe's efficiency and suitability as a point-of-care testing (POCT) alternative, offering a major improvement over traditional invasive and time-consuming laboratory methods for UA detection and monitoring.

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