Label-Free Ratiometric Electrochemiluminescence Aptasensor Based on Nanographene Oxide Wrapped Titanium Dioxide Nanoparticles with Potential-Resolved Electrochemiluminescence

A new "one-pot" hydrothermal method was developed for the preparation of electrochemiluminescence (ECL) nanoluminophores nanographene oxide wrapping titanium dioxide (nGO@TiO₂ NLPs). The characterization demonstrated that nGO@TiO₂ NLPs possessed a core-shell-like shape. The nGO@TiO₂ NLPs exhibited potential-resolved ECL property in neutral aqueous solution using K₂S₂O₈ as a coreactant. On this basis, a label-free ratiometric ECL aptasensor was designed. nGO@TiO₂ NLPs were used to fabricate the ECL interface for target recognition, potential-resolved ECL signal generation, and amplification. In the presence of cardiac troponin I (cTnI), the aptamer resides from the electrode surface owing to its rigidity, resulting in a reduction in charge transfer resistance of the modified working electrode and a ratio enhancement of two ECL signals of nGO@TiO₂ NLPs. According to the increased ECL ratio, cTnI could be determined by the ratiometric ECL aptasensor, with a linear dynamic range of 1.0 × 10⁻¹³-1.0 × 10⁻¹⁰ mol/L and a detection limit of 4.0 × 10⁻¹⁴ mol/L, which is superior to most reported electrochemical methods. This label-free ratiometric ECL strategy with self-calibrating ability and accurate, ultrasensitive, rapid, specific analytical performance showed great promise in biosensing and clinical diagnosis. The developed strategy might extend for the sensing of other protein biomarkers by using corresponding antibodies or aptamers as recognition elements.