Fabrication of Tris(bipyridine)ruthenium(II)-Functionalized Metal–Organic Framework Thin Films by Electrochemically Assisted Self-Assembly Technique for Electrochemiluminescent Immunoassay

A simple strategy for one-step fabrication of tris(bipyridine)ruthenium(II) (Ru(bpy)32+)-functionalized metal–organic framework (Ru-MOF) thin films using a self-assembly approach assisted by an electrochemical way was introduced. In this protocol, the electrochemically driven cooperative reaction of Ru(bpy)32+ as an electrochemiluminescent (ECL) probe and a structure-directing agent, trimesic acid (H3btc) as a ligand, and Zn(NO3)2 as the Zn2+ source leads to an one-step and simultaneous synthesis and deposition of the MOF onto the electrode surface. Characterization of the Ru-MOF thin films was performed with scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Scanning ion conductance microscopy was specially applied in situ to image the topography and thickness of the Ru-MOF thin films. The Ru-MOF thin films as a sensing platform show excellent ECL behavior because of plenty of Ru(bpy)32+ molecules encapsulated in the frameworks. On the basis of the Ru-MOF modified electrodes, an ultrasensitive label-free ECL immunosensing method for the human heart-type fatty-acid-binding protein has been developed with a wide linear response range (150 fg mL–1–150 ng mL–1) and a very low limit of detection (2.6 fg mL–1). The prepared immunosensor also displayed excellent stability and good specificity in the test of practical samples.