Acidic etching coupled with coordination assembly for in situ synthesis of fishbone-shaped Cu(II)-phytic acid polymer for electrochemical biosensing of microRNA-let 7a

The construction of a facile and highly sensitive electrochemical biosensor for microRNA detection has significant implications for clinical diagnostics. In this study, an interface integrating a fishbone-shaped Cu@Cu(II)-phytic acid (Cu@Cu(II)-PA) polymer was developed through in situ acidic etching coupled with coordination assembly. After further modification of electrodeposited gold nanoparticles (AuNPs), this interface served as a multiple-nanocomposite for the construction of an electrochemical biosensor for miRNA-let 7a. First, a layer of metallic copper was prepared on a glassy carbon electrode (GCE) through electrodeposition. Followed by, the acidic PA solution was dropped on the electrode, from which the metallic copper was chemically etched and the generated Cu(II) ions were reacted with PA to form Cu@Cu(II)-PA polymer through the coordination assembly. Subsequently, a layer of AuNPs was electrosynthesized on the Cu@Cu(II)-PA, acting as the matrix for pDNA immobilization. Electrochemical assays indicate that the AuNP/Cu@Cu(II)-PA composite exhibits excellent electrocatalytic activity towards H₂O₂, mimicking peroxidase. The hybridization of pDNA immobilized on the electrode surface with the target miRNA-let 7a significantly inhibits the nanozyme activity of AuNP/Cu@Cu(II)-PA, thereby enabling the detection of miRNA-let 7a based on catalytic signal variation. The analytical assay demonstrates that the target miRNA-let 7a can be analyzed over a wide concentration range from 1.0 fM to 10 nM with a detection limit as low as 0.4 fM. Furthermore, the biosensor exhibits commendable performance in the detection of miRNA-let 7a in real serum samples, highlighting its potential for clinical applications in early disease diagnosis.