High-sensitivity cholesterol biosensor based on ChOx-decorated Au-Ag@Au/PB-PEDOT: Exploring serum-saliva relationship

Elevated cholesterol is a major cardiovascular risk factor, but current detection methods are resource-intensive. Non-invasive point-of-care testing is promising yet limited by sensitivity, and the blood-saliva cholesterol correlation requires further investigation. We developed an electrochemical biosensor featuring cholesterol oxidase immobilized on screen-printed carbon electrodes (SPCE) modified with conductive Au-Ag@Au core-shell nanoparticles and Prussian blue/poly-3,4-ethylenedioxythiophene (PB-PEDOT) nanocomposites. Morphological, spectroscopic, and electrochemical analyses (including impedance spectroscopy, heterogeneous electron transfer kinetics, and active surface area quantification) confirmed the biosensor superior conductivity. The biosensor achieved exceptional performance: a broad linear range (0.01–1.0 mM), low detection limit (3.3 μM amperometric LOD; 2.8 μM via EIS), and high sensitivity (57.3 μA/mM·cm 2 amperometric; 781 Ω/mM·cm 2 impedimetric). Clinical validation demonstrated excellent agreement with standard colorimetric methods in human serum and saliva for cholesterol tested in biological compounds and robust stability. A strong serum-saliva correlation (Pearson's correlation coefficient as 0.928) supports noninvasive monitoring feasibility. The anti-interference capability of the proposed biosensor was evaluated against common interferents, including glucose, lactic acid, uric acid, ascorbic acid, bovine serum albumin, cysteine, and their mixture. The results confirmed its high specificity against these typical biological matrix components. Particularly significant is its non-invasive detection capability, which eliminates the need for painful blood draws or invasive sample collection procedures. A key innovation lies in the synergistic integration of conductive Au-Ag@Au core-shell nanoparticles with PB-PEDOT nanocomposites on SPCEs, which significantly enhances electron transfer and catalytic activity, yielding an exceptionally sensitive and stable sensing platform. The biosensor sets itself apart by achieving superior analytical performance concurrently with robust clinical validation in both serum and saliva, firmly establishing its potential for reliable non-invasive cholesterol monitoring.