Lanthanide-Incorporated PIII–SbIII-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 PIII–SbIII-heteroatom-templated tetrahedral polyoxometalate cluster [H2N(CH3)2]20Na7H7{[Er6(H2O)6][W4O16][HPSbW15O54]4}·132H2O (1). The polyoxoanion of 1 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 1 exhibits the distinctive ({W4} ⊂ {Er6} ⊂ [{PSbW15}]4) three-shell structure. Considering the electron transfer characteristics of 1, it was coelectropolymerized with N-methylpyrrole (NMPy) to fabricate the 1–PNMPy film (PNMPy = polyNMPy). Notably, the incorporation of 1 improves the electron distribution within the PNMPy backbone, thereby narrowing the band gap of PNMPy and enhancing the conductive performance of the 1–PNMPy film. Therefore, the 1–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.