High-performance disposable electrochemical sensors for creatinine derived from hollow CoNi-LDH@Creatinine-imprinted Poly(methacrylic acid) (i-PMA) composites.

Background: Layered double hydroxides (LDHs), featuring a 2D layered structure, are an emerging class of inorganic porous materials for electrochemical biosensors. Presently, they are primarily utilized in the electrochemical detection of oxygen-containing biomolecules. However, there are currently no reported LDH sensors, particularly CoNi-LDH ones, designed for the electrochemical detection of creatinine (Cre), a widely studied nitrogen-containing biomolecule. Here, to realize electrochemical detection of creatinine, a unique hollow CoNi-LDH/creatinine imprinted polymethacrylic acid (H-LDH@i-PMA) composite is developed through a pioneering combination of a hollow CoNi-LDH (H-LDH) structure and the molecular imprinting polymer (MIP) coating technique.

Results: The materials are comprehensively characterized using FT-IR, PXRD, XPS, TEM, CV, and EIS. Disposable Au-screen printed electrodes are fabricated with both H-LDH and H-LDH@i-PMA, and the sensing of Cre is subsequently investigated via cyclic voltammetry and differential pulse voltammetry methods. The H-LDH@i-PMA sensor exhibits superior porosity, a larger electroactive area, and enhanced electron-transfer kinetics in comparison to H-LDH sensor. The H-LDH@i-PMA sensor achieves a wide detection range of 0-1000 nM, accompanied by a low detection limit of 236 pM, and five-times more sensitivity for Cre than non-imprinted H-LDH sensor. Futhermore, it demonstrates robust selectivity against interferents such as ascorbic acid, uric acid, guanine, and glutamine. When tested with real salivary samples, it exhibits a recovery rate of 99.0 ± 1.80 %, and maintains excellent reusability over a period of four weeks.

Significance: These exceptional results are due to superior electroactive area, tailor-made recognition sites, and greater electron-transfer kinetics of H-LDH@i-PMA as compared to the non-imprinted LDH sensor. This is the first reported use of an LDH-based sensor for the detection of Cre, providing valuable insights into developing high-performance electrochemical sensors for various biomolecules.