Self-enhanced electrochemiluminescence immunosensor based on carboxyl-functionalized CdIn2S4 emission and Au@MoS2 resonance energy transfer for sensitive quantification of heart-type fatty acid-binding protein

In conventional co-reactant electrochemiluminescence (ECL), the efficiency of converting co- reactant into active intermediates is the primary factor limiting luminescence intensity. To address this limitation, we synthesized carboxyl-functionalized CdIn 2 S 4 (Cf-CdIn 2 S 4 ), which served dual roles as both a luminescent material and a co-reactant accelerator. As an emitter, Cf-CdIn 2 S 4 , generated strong and stable ECL signals upon excitation at −1.3 V. Furthermore, Cf-CdIn 2 S 4 exhibited remarkable electrocatalytic activity for K 2 S 2 O 8 activation. Through the In 3+ /In 2+ valence state transition, Cf-CdIn 2 S 4 significantly facilitated the conversion of S 2 O 8 2− to SO 4 ·− , achieving self-enhanced ECL signals. The pronounced quenching effect of Au@MoS 2 on the Cf-CdIn 2 S 4 ECL signal was exploited to develop a highly sensitive quenching-type ECL sensing platform for H-FABP. The developed immunosensor exhibited a broad linear detection range (10 fg/mL–100 ng/mL) and a low limit of detection (3.2 fg/mL, S/N = 3). This novel approach provides a highly sensitive and reliable platform for the early diagnosis of acute myocardial infarction and can be effectively utilized for the early screening of cardiovascular diseases and clinical monitoring of critically ill patients.