Tunable aptamer-MXene sensing interface for label-free and real-time detection of toxic pollutants in water samples

Stable and low-cost field-effect transistor (FET)-based biosensors are vital for the on-site detection of toxic pollutants in environmental monitoring applications. In this study, a tunable aptamer-MXene sensing interface was constructed to develop renewable FET biosensors. This was achieved through the reversible disulfide bond (-S-S-) reaction between the SH-Ti₃C₂T_x film and thiolated aptamer. Ti₃C₂T_x film was prepared using layer-by-layer assembly of Ti₃C₂T_x flakes and used as the conductance channel of this FET device. Then, dithiothreitol modification was carried out through the formation of Ti-S bonds. The reversible -S-S- bonds enabled the repeated regeneration of SH-Ti₃C₂T_x, which allowed deferent aptamers to be immobilized. Therefore, multiple targets could be detected with the same FET device, avoiding device-to-device variations. Three specific aptamers for microcystin-LR, β-lactam-resistant gene (β-ARG), and Hg²⁺ were adopted to demonstrate this characteristic. The prepared aptamer-MXene FET biosensor showed high sensitivity, repeatability and stability. Furthermore, a strong real-time response was observed upon exposure to the targets. This study demonstrated that constructing a tunable aptamer-MXene sensing interface is an efficient strategy for constructing cheap and renewable aptamer-MXene FET biosensors for the label-free and real-time detection of toxic pollutants.