An electrochemical biosensor for the detection of sodium ions in serum based on Ce13d DNAzyme

In this study, a Ce13d DNAzyme-based electrochemical biosensor for the detection of sodium ions (Na + ) in the serum was developed. The indium tin oxide (ITO) electrode was modified with Au gold nanoparticles (AuNPs), then immobilized with double-stranded DNA formed by thiol of substrate strand and enzyme strand bound via Au-S link. In the presence of Na + , the resulted Ce13d DNAzyme could preferentially bind Na + , and induced local folding of Ce13d to form a G-quadruplex-like structure, which enhanced binding ability to methylene blue (MB). By using the specificity of DNAzyme and change of its conformation, the quantitative detection of Na + could be achieved. Thus, the developed sensing platform could identify Na + with a linear response range of 10 nM-100 mM and a detection limit of 1.03 nM. The electrochemical biosensor also exhibited excellent selectivity for Na + in the presence of five interfering ions, including K + , Cu 2+ , Mg 2+ , Zn 2+ and Ca 2+ . Furthermore, the proposed biosensor showed satisfactory results for Na + in serum sample analysis, which highly correlated with the inductively coupled plasma atomic emission spectrometry method. This work demonstrated a simple and reliable method for Na + in serum, which opens the way for potential applications in disease diagnosis and environmental testing.