A signal-amplified ratiometric fluorescence biomimetic sensor based on the synergistic effect of IFE and AE for the visual smart monitoring of oxytetracycline

Exploring high-performance fluorescence strategies for onsite monitoring of oxytetracycline (OTC) is of great significance for protecting human health. Herein, an innovative ratiometric fluorescence biomimetic sensor featured with high sensitivity and selectivity was constructed based on magnesium and nitrogen co-doped carbon dots embedded europium metal–organic framework and incorporating molecularly imprinted polymer (Mg,N-CDs/[email protected]). In this protocol, MIP layer functioning as recognition units endowed Mg,N-CDs/[email protected] with satisfactory binding efficiency and anti-interference ability. Mg,N-CDs/Eu-MOFs as both supporter and signal tag enabled the sensor to not only demonstrate a fast fluorescence response, but also yield reverse response signals depending on the synergistic effect of inner filter effect (IFE) and antenna effect (AE), achieving signal amplification. Benefiting from the efficient dual-channel strategy, Mg,N-CDs/[email protected] exhibited a wide linear range (0.02–50 μg mL−1) with a sensitive detection limit (6.6 ng mL−1) and a marked color transformation (blue-to-red), which was highly desirable for monitoring of oxytetracycline. Simultaneously, aiming at attaining precise onsite analysis, a portable intelligent sensing platform was devised by integrating Mg,N-CDs/[email protected] and a smartphone-assisted device. The smartphone with an installed color recognizer application as signal reader and analyzer realized oxytetracycline visual sensing by capturing and digitizing fluorescence images. More significantly, the portable platform was successfully applied to the onsite monitoring of OTC in water samples and milk samples with acceptable results. Accordingly, the as-developed platform demonstrated low-cost, portability, easy implementation, desirable specificity and sensitivity, presenting great potential for point-of-care testing.