Copper-Based Metal–Organic Frameworks Loaded with Silver Nanoparticles as Electrochemical Immunosensors for Diethylstilbestrol

An ultrasensitive competitive electrochemical immunosensor for the quantitative detection of diethylstilbestrol (DES) was constructed by linear-sweep voltammetry. In this work, copper-based metal–organic frameworks [Cu3(BTC)2] loaded with silver nanoparticles (Ag NPs) served as the matrix, which causes an strong electrochemical signal of Ag/Ag+ for the detection of DES. Nevertheless, the signal was reduced by virtue of antibodies and antigens with depression of electron transfer and obstruction of signal transmission. To further decrease of the electrochemical signal, amino-functionalized hematite (α-Fe2O3–NH2), an n-type semiconductor with large steric hindrance, served as the marker. In the devised immunosensor, DES can compete with the bovine serum albumin–diethylstilbestrol-marked α-Fe2O3–NH2 (α-Fe2O3–BSA–DES) to combine antibody-specific sites. Owing to the small molecular weight of DES, it was easier to combine antibodies than α-Fe2O3–BSA–DES. Therefore, the current signal will augment with an increase of the DES concentration. This immunosensor offered an outstanding analytical performance for the quantitative detection for DES with a broad range from 0.005 to 500 ng/mL and a limit detection of about 1.67 pg/mL (S/N = 3). This biosensing system provides a straightforward and reliable platform, which has great potential application for the quantitative detection of a biomarker.