Multicolorimetric\nSensor Array Based on Silver Metallization\nof Gold Nanorods for Discriminating Dopaminergic Agents

Dopaminergic agents are compounds that modulate dopamine-related\nactivity in the brain and peripheral nerves within the pathways on\nboth sides of the blood-brain barrier. Atypical levels of them can\nprecipitate a multitude of neurological disorders, whose timely diagnosis\nsignifies not only stopping the advancement of the illness but also\nsurmounting it. A silver metallized gold nanorod (AuNRs) conditional\nsensor array, designed to detect dopaminergic agents for assessing\nnervous system disorders, yielded significant results in simultaneous\ndetection and discrimination of Benserazide (Benz), Levodopa (L-DOPA),\nand Carbidopa (Carb). The array was composed of two different concentrations\nof silver ions as sensor elements (SEs), which generated unique signatures\nindicative of the presence of reductive target analytes, triggered\nby the incongruent formation of the Au@Ag core–shell, causing\nvisual and fingerprint colorimetric patterns. Generating diverse responses\nis the key to the functionality of array-based sensing, which facilitated\nachieving spectral and color variation originating from the blue shift\nof AuNRs longitudinal localized surface plasmon resonance (LLSPR)\nin the extinction spectrum. Also, employing a smartphone camera enables\nclear visual discrimination across an extensive concentration span.\nPattern recognition through linear discriminant analysis (LDA) underscored\nthe robust discrimination accuracies of this sensor, along with quantification\nby means of partial least-squares regression (PLSR), affirming its\npotential for practical applications. Notably, the array demonstrated\nhigh sensitivity in detecting varied concentrations of target analytes,\neven in commercial drug samples. The sensor responses exhibited a\nlinear correlation with the concentrations of Benz, L-DOPA, and Carb\nranging from 1.59 to 100.0, 5.26 to 100.0, and 5.32 to 100.0 μmol\nL<sup>–1</sup>, respectively, and the minimum detectable concentrations\nfor Benz, L-DOPA, and Carb were measured at 0.53, 1.75, and 1.77 μmol\nL<sup>–1</sup>, respectively. The implemented machine-learning-empowered\narray-based sensor represents advancements in dopaminergic agent tracing\nand naked eye detection.