Gold Nanorods as Plasmonic-based Optical Biosensor for Creatinine Detection

This work aims to develop a label-free and high-sensitivity biosensing platform for creatinine detection to enable early diagnosis of chronic kidney disease. We investigated the optical response of gold nanorods' localized surface plasmon resonance (LSPR) towards low-concentration creatinine biomarker. The unique optical properties of metallic nanorods with two plasmonic modes assert nanorods as a more robust platform than metallic nanospheres with sensing sensitivity improved at an increased aspect ratio. Utilizing the electrostatic adsorption from piranha substrate treatment, an adequate interparticle separation and uniform distribution of immobilized gold nanorods is obtained, allowing plasmon localization to be preserved for analyte sensing. The electrostatic interaction between the carbonyl group in creatinine molecules and the cationic headgroup capping the gold nanorods serves the adsorbate-induced sensing principle. The longitudinal LSPR mode shift yielded a linear relationship with increasing creatinine concentration, with sensitivity as high as 9.064 µm dL g<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> is recorded. The limit of detection (LOD) and the limit of quantification (LOQ) are determined to be 0.645 mg/dl and 0.712 mg/dl, respectively.