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Self-assembled monolayers for Uricase enzyme absorption immobilization on Screen-printed gold electrodes modified.
1 , 2 , * 1
1  Bioelectronics Section, Department of Electrical Engineering, CINVESTAV-IPN, 07360 Mexico City, Mexico.
2  CONACyT-CIMAV S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, 31136 Chihuahua, CHIH, Mexico.
Academic Editor: Oleh Smutok


Miniaturized and integrated devices for fast determination of clinical biomarkers is of high demand in the current healthcare environment. In this work, we present a functionalized self-assembled monolayer (SAM) on the gold surface of a screen-printed electrode (AuSPE). The device was applied for uric acid (UA) detection, a biomarker associated with arthritis, diabetes mellitus, and kidney function. Prior to SAM formation AuSPE was subjected to pretreatment with KOH and Au electrodeposition to provide additional roughness to the substrate. The SAM was formed in the AuSPE/KOH/AuNPs surface by cysteamine method, which was carried out when working surface dipping in cysteamine solution at 20 mM for 24 hours, and rinsed with ethanol and milli-Q water, then uricase enzyme was immobilized through physical absorption, at room temperature with an average humidity percentage recorded of 86%, the duration of this process was 1 hour and the AuSPE/KOH/AuNPs/SAM/Uox biosensor was rinsed with phosphate saline buffer (PBS) and milli-Q water prior to the UA detection process. The physical and electrochemical characterization of AuSPE modification was carried out by Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV). The calibrated data of the Au/KOH/AuNPs/SAM/Uox biosensor showed a linear relation in the range of 50 – 1000 µM, a sensibility of 0.1449 µA/[(µM)cm2], and a limit of detection (LOD) of 4.4669 µM. The Au/KOH/AuNPs/SAM/Uox also exhibited a good selectivity for UA in presence of ascorbic acid. Moreover, the methodology exhibited good reproducibility, stability, and sensitive detection of UA. This performance of the proposed biosensor is in good accordance with clinical needs, and can be compared with previous biosensors based on nanostructured surfaces of high fabrication complexity.

Keywords: AuNPs, AuSPE, Biosensor, CV, electrochemist, uric acid, uricase, SAM.