Lanthanide-Incorporated P^III–Sb^III-Heteroatom-Templated Tetrahedral Heteropolyoxometalate Cluster for Detecting Early Tumor Marker MicroRNA-155

Heteropolyoxometalates have garnered widespread attention owing to their diverse structures and intriguing physicochemical properties. Herein, we successfully synthesized a unique lanthanide-incorporated P^III-Sb^III-heteroatom-templated tetrahedral polyoxometalate cluster [H₂N(CH₃)₂]₂₀Na₇H₇{[Er₆(H₂O)₆][W₄O₁₆][HPSbW₁₅O₅₄]₄}·132H₂O (<b>1</b>). The polyoxoanion of <b>1</b> can be perceived as four trilacunary Dawson [HPSbW₁₅O₅₄]^11- {PSbW₁₅} building blocks encapsulating a deca-nuclear heterometallic [Er₆(H₂O)₆W₄O₁₆]¹⁰⁺ cluster. This heterometallic cluster comprises an inner tetrahedral [W₄O₁₆]^8- ({W₄}) core surrounded by an octahedral [Er₆(H₂O)₆]¹⁸⁺ ({Er₆}) shell. Consequently, the polyoxoanion of <b>1</b> exhibits the distinctive ({W₄} ⊂ {Er₆} ⊂ [{PSbW₁₅}]₄) three-shell structure. Considering the electron transfer characteristics of <b>1</b>, it was coelectropolymerized with <i>N</i>-methylpyrrole (NMPy) to fabricate the <b>1</b>-PNMPy film (PNMPy = polyNMPy). Notably, the incorporation of <b>1</b> improves the electron distribution within the PNMPy backbone, thereby narrowing the band gap of PNMPy and enhancing the conductive performance of the <b>1</b>-PNMPy film. Therefore, the <b>1</b>-PNMPy film is utilized as the modified electrode material to construct an electrochemical biosensor for the sensitive detection of the tumor marker microRNA-155. This research not only provides a viable approach for the fabrication of multishell heteropolyoxometalates but also promotes the exploration and application of multicomposition polyoxometalates in electrochemical biosensing microRNA.