Highly stable Ni-MOF comprising triphenylamine moieties as a high-performance redox indicator for sensitive aptasensor construction.

Electroactive metal-organic frameworks (MOFs) with large surface area and manipulatable structural properties show promise as a new type of signal probe for electrochemical biosensing application. In this work, an electroactive Ni-MOF, assembled by the redox-active ligands 4,4',4″-Tricarboxytriphenylamine (HTCA), a triphenylamine derivatives, as the electroactive source and magnetic ordered NiO clusters as electronic transport nodes, is first designed and applied for electrochemical aptasensing of thrombin (Tb). The designed Ni-MOF probe realizes a stable and sensitive electrochemical signal output based on simple sandwich-type aptasensing because the high-content TCA active sites and good magnetic ordered intermediate of NiO clusters are periodically arranged in well-defined porous structure of the MOF. The Ni-MOF probe assembled by redox-active ligand presents the high stability and can be directly applied in electrochemical aptasensor, avoiding any post-modification and the addition of redox mediators. As a result, the constructed electrochemical aptasensor shows a wide linear relationship for Tb from 0.05 pM to 50 nM and a detection limit of 0.016 pM (S/N = 3). Furthermore, the proposed aptasensor is successfully applied to analysis of target Tb in real serum sample with satisfactory results. The present work indicates that fabricating a redox-active organic molecule in functionalized MOFs offer a feasible strategy to design high-stable electroactive MOFs for construction of electrochemical biosensors with simplicity, high selectivity and sensitivity.