Structural and Electrochemical Analysis of Copper-Creatinine Complexes: Application in Creatinine Detection
Kamonwad Ngamchuea, Suttipong Wannapaiboon, Papawit Nongkhunsan, Pussana Hirunsit, Ittipon Fongkaew
Abstract
The formation of complexes between copper ions and biomolecules plays important roles in biological systems. In this work, the structures and electrochemical properties of copper-creatinine complexes were investigated by both experimental and computational approaches. DFT calculation revealed the possible structures of copper-creatinine complexes and provided the data of formation energies, bond lengths, and charge distribution. The properties of the complexes were further investigated by cyclic voltammetry, UV-visible spectrophotometry, X-ray absorption spectroscopy, and scanning electron microscopy. The combination of experimental and computational findings revealed that Cu II binds with creatinine via the endocyclic nitrogen. In aqueous environment, the [Cu(creatinine) 2 (H 2 O) 2 ] 2+ complex is formed. The reduction of [Cu(creatinine) 2 (H 2 O) 2 ] 2+ formed a stable 1:4 complex between Cu I and creatinine. Importantly, the understanding of the electrochemical behaviors of copper-creatinine complexes leads to the development of a novel sensor for the detection of creatinine, a biomarker for kidney diseases. Although creatinine itself is not electroactive, the complex formation with copper allows the species to be detected electrochemically with the sensitivity of 6.09 ± 0.13 μ A mM −1 and the limit of detection (3s B /m) of 35 μ M.