Multiplexed Microfluidic-Based Sensor Using Photopolymerized Molecularly Imprinted Polymer Structures for the Detection of Estrogens in Wastewater

Trace estrogens in water sources pose growing environmental and public health concerns due to their endocrine-disrupting properties. In this work, we propose a versatile approach using a molecularly imprinted polymer (MIP)-based highly selective and sensitive multiplexed microfluidic-based sensor for the detection of three key estrogens: estrone (E1), 17β-estradiol (E2), and estriol (E3), employing electrochemical impedance spectroscopy (EIS) as a read-out technique. The MIP sensors used to detect the different estrogens were in situ photopolymerized on the functionalized nanocrystalline diamond-coated substrates, employing N,O-bismethacryloyl ethanolamine (NOBE) as a bifunctional monomer/cross-linker. The versatility also arises from the minimal variation in the formulations used for MIP sensors to detect a family of estrogens, where the variation is related only to the target molecule of interest in the composition. The MIP sensors were able to detect the respective analyte with a detection limit of 0.5 nM in the buffer and in wastewater samples with high selectivity. The impedance signal after analyte addition (100 nM) reached a steady state in a short time (10 min). EIS results were also validated using complementary techniques, such as UV–vis spectroscopy for a selected high concentration (500 nM) and gas chromatography–mass spectrometry (GC–MS) for a lower concentration range (5–50 nM). The selectivity of each MIP sensor for a specific target molecule was verified by using its respective structural analogues. Additionally, the selectivity of the E2 MIP sensor was also verified by GC–MS analysis by using a solution containing a mixture of estrogens. This work highlights the synergistic advantage of combining microfluidic-assisted MIP synthesis with multiplexed impedimetric sensing, offering a robust platform for the environmental monitoring of a class of molecules in complex water matrices.