Magnetic molecular imprinting-restricted access materials combined with luminous boric acid carbon dots for fluorescence monitoring of Tetracycline

In biological samples, the accurate fluorescence detection of tetracycline (TC) affects by not only the interfering molecules but also the nonspecific adsorption of marcromolecules such as proteins. This study developed magnetic molecular imprinting–restricted access materials (MMIP–RAMs) for TC detection. The MMIP–RAMs was synthesized using magnetic poly(chloromethylstyrene-co-divinylbenzene) (Fe₃O₄@P_VBC/DVB) microspheres as the substrate, through two-step surface initiated-atom radical polymerization, TC-molecular imprinting polymers as the recognition sites and zwitterionic phosphorylcholine (MPC) polymers as the anti-protein sites were successively constructed onto Fe₃O₄@P_VBC/DVB surface. The resulting MMIP–RAMs of Fe₃O₄@P_VBC/DVB@MIP@poly(MPC) exhibited a high TC adsorption capacity (138.6 mg g⁻¹) and an anti-protein capacity (above 96.8 %). Meanwhile, boric acid-containing carbon dots (BA-CDs) were prepared by citric acid and 3-aminobenzeneboronic acid precursors through hydrothermal method. In fluorescence detection, MMIP–RAMs could specially recognize TC by its imprinted cavity, after adding luminous BA-CDs, the combined MMIP–RAMs/TC could further bond BA-CDs with aid of boron affinity forces between cis-diol in TC and the boric acid groups in BA-CDs, forming MMIP–RAMs/TC/BA-CDs sandwich particles. The changes of pristine and remaining fluorescence intensity of BA-CDs had a linear relationship to TC content, establishing a simple fluorescence detection method. The fluorescence detection of TC was in the range of 44 − 264 ng mL⁻¹ and low detection limit of 7.1 ng mL⁻¹. When applying this method in milk, the fluorescence interference of background protein was completely eliminated by MMIP–RAMs to guarantee the accuracy of fluorescence determination, the resulting recovery rates of TC in milk were 100.0 − 105.4 % with relative standard deviations of 4.8 − 7.9 %, highlight application potential.