A dual-recognition UCNPs sensor for sensitive detection of tetracycline in food using computer-designed silica-grafted paper microfluidic strategy

The growing concern over elevated tetracycline (TC) residues in food has become a significant issue for public health. Herein, we propose an upconversion sensor integrated with a computer-designed, silica-grafted paper microfluidic device (SiO₂@μPAD) that utilizes a dual-recognition strategy. Both Cu²⁺ ions and an aptamer on the MIL-53(Fe) surface specifically recognize TC. Initially, upconversion nanoparticles (UCNPs) were coated with complementary DNA (cDNA) to create signal probes, designated as UCNPs-cDNA. Then, the aptamer and Cu²⁺ were assembled onto the outer layer of MIL-53(Fe), resulting in the formation of capture probes, Apt-MIL-53(Fe)@Cu²⁺. By leveraging the principle of base complementarity, dual-recognition sensing probes, UCNPs-MIL-53(Fe)@Cu²⁺, were synthesized. SiO₂@μPAD, designed and fabricated using computer-aided techniques and a printer, served as an ideal sensor carrier, with UCNPs-MIL-53(Fe)@Cu²⁺ deposited on its surface for in-situ TC detection. In the presence of TC, the aptamer recognition and TC-Cu²⁺ chelation induced a TC-bridged strategy, enhancing electrostatic repulsion between UCNPs-cDNA and Apt-MIL-53(Fe)@Cu²⁺. This disruption of Förster resonance energy transfer (FRET) triggered a strong "signal-on" effect from the UCNPs. Under optimized conditions, the sensor exhibited a linear detection range of 20–10,000 μg/L ( R ² = 0.997), with a limit of detection (LOD) of 1.18 μg/L. Furthermore, the sensor's precision and accuracy were validated against high-performance liquid chromatography (HPLC) results, showing satisfactory outcomes in detecting TC in fish, tap water, milk, and pork, with a relative standard deviation (RSD) of less than 5.71 %. • A computer-designed UCNPs-MIL-53(Fe)@Cu 2 + /SiO 2 @μPAD sensor was proposed to detect TC. • A dual-recognition strategy was presented to improve the sensitivity of UCNPs sensor. • MIL-(53)Fe@Cu 2+ can effectively quench the fluorescence of UCNPs. • Computer was utilized to design μPAD with desired pattern for in-situ detection. • Silica was coated onto μPAD to enhance its hydrophobicity.