Single-step printed graphene–Prussian blue analog ink for dopamine-modified electrochemical sensor: Application to simultaneous detection of HVA and VMA in urine samples

Abstract

This study presents, for the first time, the meticulous integration of lab-made Prussian blue analogs (PBAs) into graphene ink. The PBAs were methodically incorporated into graphene ink to produce a homogeneous and uniform composite material. Subsequently, the formulated ink was screen-printed onto a substrate, which resulted in a screen-printed graphene–PBAs incorporation electrode (SPG(PBAs)E). To further enhance surface functionalization, this design is modified with dopamine (DA). The DA-modified SPG(PBAs)E (DA/SPG(PBAs)E) enables the simultaneous electrochemical detection of homovanillic acid (HVA) and vanillylmandelic acid (VMA), two key neurotransmitter metabolites. The synergistic properties of graphene and PBAs provide a high surface area, conductivity, and electrocatalytic activity, while dopamine acts as a bioinspired linker, improving sensitivity for the detection. The developed sensor demonstrated excellent sensitivity, selectivity, and stability in complex matrices. After the systematic optimization of ink formulation and electrochemical parameters, the linear concentration ranges were 5–50 µM for HVA and 1–25 µM for VMA, with detection limits of 1.46 and 0.29 µM, respectively. In practical applications, the proposed electrode effectively analyzed HVA and VMA in human urine samples, yielding satisfactory results with recovery values falling within an acceptable range of 89.60 – 118.46 %. This integrated approach offers a promising strategy for developing compact, cost-effective, and point-of-care diagnostic tools for clinical neurochemical monitoring.