A sandwich-type electrochemiluminescence biosensor based on Ni₃(HAB)₂/Au@ZnNiAl-LDH/Ru@MIL-53(Al)-NH₂ for ultra-sensitive detection of microRNA-155

A novel electrochemiluminescence (ECL) biosensor was developed for the ultrasensitive detection of miRNA-155, based on the synergistic combination of multifunctional nanomaterials. The biosensor employed a conductive metal–organic framework (MOF), Ni₃(HAB)₂ (HAB = hexaaminobenzene), as the substrate material. The unique π-electron conjugated structure of Ni₃(HAB)₂ endowed the biosensor with excellent electron transport properties, significantly enhancing its sensitivity. Furthermore, the innovative preparation of Au@ZnNiAl-LDH nanocomposites, characterized by a high specific surface area was employed to synergistically enhance the catalytic performance of the biosensor in conjunction with Ni₃(HAB)₂. The Au@ZnNiAl-LDH also provided stable anchoring sites for the capture unit, comprised of a DNA tetrahedron hairpin composite structure (DT-HP). Additionally, a porous aluminum-based metal–organic framework (MIL-53(Al)-NH₂) was utilized to encapsulate Ru(bpy)₃²⁺, constructing a Ru@MIL-53(Al)-NH₂ signal unit that effectively improved the stability of the ECL signal. Under optimal conditions, the ECL intensity of the biosensor exhibited a robust linear relationship with the logarithm of miRNA-155 concentration over a range 3 fM to 1 nM, achieving a detection limit as low as 0.9 fM. Moreover, the biosensor demonstrated exceptional specificity, selectivity, and stability, highlighting its significant potential for applications in bioanalysis and clinical diagnosis, particularly for the early diagnosis of tumor.