Electrochromic platform for the visual detection of the neuroblastoma biomarkers vanillylmandelic acid and homovanillic acid

Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are biomarkers for the diagnosis and course-of-disease monitoring of malignant tumor neuroblastomas, which endanger infants and children. Herein, we demonstrated a proof-of-concept visual detection of VMA and HVA on an electrochromic basis, in which the viologen 1,1'-dibenzyl-4,4'-bipyridinium dichloride was used as a coloration chromophore. It was found that VMA and HVA can be used as effective electron mediators to improve the electrochromic performance of devices. It is interesting to note that VMA and HVA reduce the driving voltage of electrochromic devices (ECDs) down to -1.0 V, which is lower than that (-2.1 V) achieved without these additives, and the coloration of ECDs is undoubtedly dependent on the concentration of VMA and HVA from 0.8 to 10^-6 mol L^-1. Thus, this study presents an ECD platform as a breakthrough strategy for the facile, routine and portable visual detection of the neuroblastoma biomarkers VMA and HVA with obvious advantages over other detection techniques such as HPLC/MS used in clinical diagnosis.