Ultrasensitive Biosensor Based on Efficient Antifouling Interface and Dual Signal Amplification Strategy for Trace Detection of Thrombin in Serum

The presence of a large number of interfering substances in complex biological samples can affect the detection sensitivity and accuracy of the sensors. To address the aforementioned issues, an ultrasensitive electrochemiluminescence (ECL) biosensor based on an efficient antifouling interface and dual signal amplification strategy was developed for thrombin (TB) detection in serum samples. Specifically, poly-tannic acid doped polyaniline (PTA-PANI) was modified on the sensing interface as an antifouling film to resist nonspecific adsorption of interfering biomolecules in serum. Second, EuTb-MOF with high ECL efficiency was prepared as the luminophore, in which Tb³⁺ transferred the energy from itself and ligand to Eu³⁺, achieving effective signal self-enhancement. At the same time, Ag/CoFe-LDH@GO was introduced to promote the reduction of S₂O₈^2- due to the valence state cycling of Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺, as well as the synergistic catalysis of Ag NPs, thus further improving ECL emissions. Based on these sensing strategies, the proposed biosensor showed long service life and high detection sensitivity and accuracy, with a wide linear range of 10 fM to 100 nM and a low detection limit of 3.62 fM (S/N = 3). This study provides a positive reference for trace detection of TB in a complex serum medium.