Early detection of hyperuricemia using hybrid Au– ZnO biosensor and Kretschmann-based SPR at visible optical wavelengths

Hyperuricemia is a form of disease that stems from excessive amount of uric acid due to excessive purine-rich food consumption or insufficient excretion in a human body hence the need for a reliable non-invasive sensor to detect it. This study explores Surface Plasmon Resonance based on Kretchman configuration (K-SPR) as a rapid, highly sensitive and impeccably accurate biosensor. K-SPR technique was proven as the best method as it offers label-free detection of biomarkers. Experimental work was executed using Bionavis K-SPR Navi™-200 utilizing gold-zinc oxide (Au-ZnO) hybrid thin films as the sensing layer for uric acid level measurements. The minimum reflectivity, R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</inf>, full-width-at-half-maximum (FWHM), sensitivity and Q-factor was calculated to determine the dependability of these layers as a sensing material. At 670 nm and 785 nm optical wavelength, respectively, the FWHM of Au-ZnO thin films produced in air was 1.271072° and 0.508751°, while their R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</inf> values were 0.08747 and 0.11343. For uric acid sensing of 0.6mM, 1.2mM, 1.8mM, 2.4mM and 3.0mM, Au-ZnO has an average sensitivity of 0.05193°/mM for 670 nm and 0.04150°/mM for 785 nm. Average Q-factor obtained was 0.04085 mM<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 0.04787 mM<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> under 670 nm and 785 nm respectively. Lower detection limit of 0.5 mM uric acid was tested resulting in the best sensitivity of 0.0511°/mM at 670 nm optical wavelength.