An antibody-free and signal-on type electrochemiluminescence sensor for diethylstilbestrol detection based on magnetic molecularly imprinted polymers-quantum dots labeled aptamer conjugated probes

An antibody free and signal-on type electrochemiluminescence(ECL) sensor was developed for diethylstilbestrol (DES) detection using magnetic surface magnetic molecular imprinting polymers (MMIPs) - aptamer labeled CdS quantum dots (CdS QDs) conjugated probes. Firstly, the MMIPs were synthesized through employing 4″-hydroxypropiophenone as mimicking template to form imprint sites on the poly-dopamine coating covering core-shell Fe3O4@SiO2 (MMIPs). Secondly, the aptamer which epitope is phenol group of 17β-estradiol (E2), was chosen to label on CdS QDs to form CdS-Apt signal tag and recognize phenol group of DES. When the target, MMIPs and CdS-Apt was incubated together, a sandwich MMIPs-DES-CdS-Apt composite was constructed. It was then adsorbed on the interface of a screen printed carbon electrode (SPCE) by external magnetic field, then emit electrochemical luminescence signal at potential − 1.1 V. The signal intensity was in proportion to the logarithm of DES' concentration from 0.3 to 1.0 × 105 pg ml− 1, with the detection limit (LOD) of 0.1 pg ml− 1 (S/N = 3). Several fish samples were tested by the sensor which showed high selectivity and good recoveries between 80% and 120% with consistent results as that of conventional ELISA. Since there have been no reports of aptamer for DES, we use E2 aptamer to recognize phenol epitope of DES, then MMIPs towards another epitope to form a sandwich complex. Thus a signal-on and sandwich sensor was fabricated. Moreover, no expensive antibody was employed for fabricating the sensor. Its selectivity and sensitivity were higher than the same type of sensor based on sole aptamer or MIPs probe. The assay can be explored to detect other analytes while changing the corresponding aptamer and imprinting template.