Enzyme mimetic electrochemical sensor for salivary nitrite detection using copper chlorophyllin and carbon nanotubes-functionalized screen printed electrodes

Abstract

Electrochemical detection of salivary nitrite (NO₂⁻) is gaining importance in establishing screening protocols for identifying people with oral diseases and other clinical conditions associated with nitric oxide biology. This work demonstrates smart sensing of salivary NO₂⁻ levels through a point-of-care (POC) electrochemical approach. The electrochemical sensor was prepared using copper chlorophyllin (CuCP) as an enzyme mimic and electrodeposited onto multi-walled carbon nanotubes (MWCNTs)-functionalized screen-printed carbon electrodes. The morphology and composition of the nanocomposite-modified printed sensors were evaluated using field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical techniques such as cyclic voltammetry and linear sweep voltammetry were used to characterize the electrochemical sensor and measure the nitrite levels. The modified CuCP-MWCNTs-SPCE allowed the electrochemical sensing of nitrite over a wide range of concentrations (10 μM to 10 mM) in standard and human saliva samples. The electrochemical activation of CuCP on MWCNTs enabled the sensitive detection of nitrite. The practical applicability of the enzyme mimic-based sensing platform was tested in real human saliva samples (n = 5) to enable POC measurement. The results of the electrochemical sensors are validated with a commercial Griess reagent test.