Lanthanide Coordination Polymer Nanoparticles as an Excellent Artificial Peroxidase for Hydrogen Peroxide Detection

Lanthanide coordination polymer nanoparticles (Ln-CPNs) have been recently demonstrated as excellent platforms for biomolecule detection. In this work, we synthesized novel cerium coordination polymer nanoparticles ATP-Ce-Tris CPNs in a simple and quick way using ATP molecules as the biocompatible ligands to Ce³⁺ ions in tris­(hydroxymethyl)­aminomethane hydrochloric (Tris-HCl) solution. In view of the excellent free radical scavenging property of cerium compounds, which is ascribed to the mixed valence state (Ce³⁺, Ce⁴⁺) and the reversible switch from Ce³⁺ to Ce⁴⁺, the synthesized ATP-Ce-Tris CPNs was used as artificial peroxidase to selectively and sensitively detect H₂O₂. The sensing mechanism depends on the oxidation of the fluorescent ATP-Ce­(III)-Tris CPNs to nonfluorescent ATP-Ce­(IV)-Tris CPNs by H₂O₂. Compared with those inorganic cerium oxide sensors, this kind of fluoresence ATP-Ce-Tris CPNs sensor needs no additional organic redox dye, such as ABTS (2,20-azino-bis­(3-ethylbenzthiazoline-6-sulfonic acid), TMB (3,3,5,5-tetramethylbenzidine), or fluorescein as signal molecules. Moreover, such ATP-Ce-Tris CPNs sensor exhibited a more sensitive response to H₂O₂ with a detection limit down to 0.6 nM, which is 2 orders of magnitude lower than those of cerium oxide sensors. This sensing platform was further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase (GOx) for the oxidation of glucose and formation of H₂O₂.