Label-free electrochemiluminescence aptasensing platform: Au-LDH-C3N4 nanocomposite for ultrasensitive carcinoembryonic antigen detection.

Carcinoembryonic antigen (CEA), a crucial non-specific tumor biomarker, exhibited a normal serum level of 2.5-5.0 ng/mL in healthy individuals. Elevations beyond this range signify increased tumor risk, underscoring the critical need for early biomarker detection. This study developed an inhibited electrochemiluminescence (ECL) aptasensor for ultrasensitive CEA detection, leveraging an Au-LDH-C3N4 composite as both the luminophore and sensing platform. The synthesis of Au-LDH- C3N4 involved the initial preparation of C3N4 by thermal pyrolysis of melamine, the subsequent in-situ growth of cobalt-iron layered double hydroxide (LDH) to form LDH-C3N4, and the final in-situ deposition of Au NPs. The resulting Au-LDH-C3N4 nanocomposite integrated the advantages of its components: the LDH-C3N4 heterojunction enhanced ECL stability and charge separation, oxygen vacancies promoted the generation of sulfate radicals (SO4·⁻), and Au NPs improved electron transfer. Leveraging these synergistic effects, a label-free ECL sensing platform was constructed. The design of the nucleic acid probes using a complementary single-stranded DNA as a stable anchor and a specific aptamer for target recognition-ensured effective surface immobilization and high recognition specificity. The fabricated aptasensor achieved remarkable performance for CEA detection, featuring an extensive linear range (0.001 to 20 ng/mL) and an exceptionally low detection limit (0.3 pg/mL based on 3σ/S). In addition, the prepared aptasensor was successfully applied to serum analysis resulting in satisfactory results. This work presented the development of Au-LDH-C3N4-based ECL aptasensors and established an effective strategy for early detection of CEA.