Prussian Blue/Carbon Nanotube Sensor Spread with Gelatin/Zein Glaze: A User-Friendly Modification for Stable Interference-Free HO Amperometry.

We report the production and characterization of effective amperometric sensors for cathodic hydrogen peroxide (HO) detection. The proposed electrodes involve a combination of a HO-signaling Prussian Blue (PB)/carbon nanotube (CNT) layer with a glaze of the biopolymers gelatin (top) and zein (beneath) for protection against PB leakage. The sandwich-type sensor was constructed through simple "drop and dry" steps with (1) suspensions of the CNTs in a soluble PB solution, (2) zein in ethanol, and (3) gelatin in water, applied sequentially to the carbon working electrode disk of a screen-printed carbon electrode (SPCE) platform. The PB in the signaling layer acted as the electrocatalyst for HO reduction at -150 mV vs Ag/AgCl/3 M KCl, enabling cathodic HO amperometry with good target proportionality. Calibration trials confirmed the linearity of the response up to 700 μM ( > 0.998), with a sensitivity of 0.425 μA μM cm and a practical detection limit of 1 μM. Quantification of HO in model and real samples with gelatin-zein-PB/CNT-SPCEs had a recovery of close to 100% of the true value. Since they are easily and cheaply made and yield accurate target assessments, gelatin-zein-PB/CNT-SPCEs are an ideal tool for electrochemical HO analyses in human body fluids, health care products, and samples from industries that use HO as a bleach and germicide. Workers with little experience in sensor fabrication and limited funding will particularly benefit from utilization of the proposed HO probes, which as well as being used in HO testing also have a potential application as the transducer unit of oxidase-based biosensors with amperometric HO readout.