Electrochemical Biosensor Composed of Silver Ion-Mediated dsDNA on Au-Encapsulated Bi Se Nanoparticles for the Detection of H O Released from Breast Cancer Cells.

A newly developed electrochemical biosensor composed of a topological insulator (TI) and metallic DNA (mDNA) is fabricated. The bismuth selenide nanoparticle (Bi Se NP) is synthesized and sandwiched between the gold electrode and another Au-deposited thin layer (Bi Se @Au). Then, eight-silver-ion mediated double-stranded DNA (mDNA) is immobilized onto the substrate (Bi Se @Au-mDNA) for the further detection of hydrogen peroxide. The Bi Se NP acts as the electrochemical-signal booster, while unprecedentedly its encapsulation by the Au thin layer keeps the TI surface states protected, improves its electrochemical-signal stability and provides an excellent platform for the subsequent covalent immobilization of the mDNA through Au-thiol interaction. Electrochemical results show that the fabricated biosensor represents much higher Ag redox current (≈10 times) than those electrodes prepared without Bi Se @Au. The characterization of the Bi Se @Au-mDNA film is confirmed by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetry. The proposed biosensor shows a dynamic range of 00.10 × 10 m to 27.30 × 10 m, very low detection limit (10 × 10 m), unique current response (1.6 s), sound H O recovery in serum, and substantial capability to classify two breast cancer subtypes (MCF-7 and MDA-MB-231) based on their difference in the H O generation, offering potential applications in the biomedicine and pharmacology fields.