| At present,veterinary drugs remaining in animal-derived food have seriously endangered human health.Therefore,it is crucial to develop a high-precision detection technology that integrates separation,enrichment,and identification for monitoring veterinary drugs remaining in food.Fluorescence analysis holds the merits of simplicity,low-cost,ultra-fast responses,high sensitivity and easy implementation of visualization monitoring capabilities,which enables it to be an efficient and sensitive means of detecting typical hazardous substances in food.In addition,with the development of nanotechnology,some innovative fluorescent biomimetic sensing nanoprobes continue to emerge,resulting in unprecedented development of the selectivity,stability,reproducibility,and sensitivity of fluorescence detection.Four novel fluorescent biomimetic sensing probes based on the unique optical properties of carbon dots and lanthanide metal-organic frameworks combined with "biomimetic antibodies" were constructed for highly selective and highly sensitive fluorescent detection of antibiotic drugs(oxytetracycline)and antiviral drugs(ribavirin).This work further explored the interaction mechanism between target molecules and probes,and solves the problem of matrix interference in complex samples,thereby realizing the highly selective identification and accurate detection of veterinary drugs remaining in food.1.Fluorescence detection of oxytetracycline based on Mg,N-CDs functionalized biomimetic sensing probeA novel fluorescent biomimetic sensing probe(Mg,N-CDs@MIP)based on the encapsulation of magnesium and nitrogen co-doped carbon dots(Mg,N-CDs)into molecularly imprinted polymer was prepared.The developed probe can be utilized for the efficient and sensitive fluorescence detection of oxytetracycline(OTC)based on the inner filter effect(IFE).The fluorescence enhancement strategy of magnesium and nitrogen co-doping enabled the constructed Mg,N-CDs@MIP composite probe to exhibit sensitive fluorescence response to OTC.Meanwhile,the introduction of imprinted sites endowed Mg,N-CDs@MIP with good specific recognition ability,thus avoiding the tedious sample preparation process.Compared with non-imprinted polymer(Mg,N-CDs@NIP),the resulting Mg,N-CDs@MIP displayed higher binding efficiency and affinity to OTC because of the integration of fluorescence selectivity of Mg,N-CDs and high specific recognition ability of MIP.Additionally,the probe was applied for determination of OTC,and its fluorescence intensity was linearly quenched with the increasing concentration of OTC from 0.125 μg mL-1 to 40 μg mL-1 with a detection limit of 41.3 ng mL-1.Finally,Mg,N-CDs@MIP was successfully utilized for OTC detection in milk samples,and the results obtained were consistent with those obtained by HPLC.Therefore,Mg,N-CDs@MIP has great potential for OTC quantitative analysis.2.Fluorescence detection of oxytetracycline based on Mg,N-CDs@MIL-101 functionalized biomimetic sensing probeA novel Mg,N-CDs@MIL-101 composite was first prepared by room temperature stirring method based on encapsulation of Mg,N-CDs(guest)in metal-organic framework MIL-101(host)with high porosity and large surface area.Afterward,a novel fluorescent biomimetic sensing probe(Mg,N-CDs@MIL-101@MIP)was fabricated through the sol-gel technology in mixed solutions containing OTC(template),3-aminopropyl triethoxysilane(functional monomer)and tetraethyl orthosilicate(cross-linker).MIL-101 as the protective shell of Mg,N-CDs and supporter not only improved the mass transfer rate and adsorption capacity of the probe,but also further enhanced the stability of the probe.The ultra-small size of Mg,N-CDs facilitated its efficient encapsulation,avoiding the multi-step modification of the probe.Moreover,the unique fluorescence properties of Mg,N-CDs enabled Mg,N-CDs@MIL-101@MIP to exhibit a sensitive fluorescence response towards OTC.The modification of the imprinted layer endowed Mg,N-CDs@MIL-101@MIP with the outstanding anti-interference ability.Under optimal detection conditions,Mg,N-CDs@MIL-101@MIP realized the fast and efficient quantitative determination for OTC based on IFE,and its fluorescence intensity was linearly quenched with the increasing concentration of OTC from 0.05 μg mL-1 to 40 μg mL-1 with a detection limit of 16.8 ng mL-1.The probe was finally applied to OTC determination in milk samples,and the results obtained were consistent with those obtained by HPLC.Therefore,Mg,N-CDs@MIL-101@MIP provides a satisfactory detection platform for OTC monitoring in complex samples.3.Ratiometric fluorescence detection of oxytetracycline based on Mg,N-CDs/Eu-MOFs functionalized biomimetic sensing probeA facile and efficient dual-channel ratiometric fluorescent biomimetic sensing probe(Mg,N-CDs/Eu-MOFs@MIP)was constructed based on carbon dot-functionalized europium metal-organic framework and incorporating molecularly imprinted polymer,which can realize the specific recognition and sensitive detection of trace OTC.In the presence of OTC,the blue fluorescent of Mg,N-CDs(445 nm)was validly quenched thanks to IFE,while red fluorescence of Eu3+(620 nm)was significantly increased because of the"antenna effect"(AE).Herein,the efficient dual-channel strategy based on the synergistic effect of IFE and AE endowed ratiometric fluorescent sensor(Mg,N-CDs/Eu-MOFs@MIP)with more prominent advantages than the single emission fluorescent probe(Eu-MOFs@MIP),such as a wider linear range(0.02-50 μg mL-1),lower detection limit(6.6 ng mL-1),as well as remarkable fluorescent color evolution(blue-to-red).Meanwhile,the high porosity and large surface area of the metal-organic framework enabled the sensing system to reach adsorption equilibrium within 2 min,shortening the sample analysis time.More importantly,with the decoration of imprinting layer,Mg,N-CDs/Eu-MOFs@MIP-based ratiometric fluorescence sensor exhibited superior binding efficiency and satisfactory specificity for OTC in real sample detection.Additionally,taking account of the requirements of onsite quantification in practical applications,a portable intelligent sensing platform was devised by integrating Mg,N-CDs/Eu-MOFs@MIP and smartphone-assisted optical detection device,providing a novel strategy for the point-of-care testing(POCT)of trace OTC in real samples.4.Ratiometric fluorescence detection of ribavirin based on BA-LMOFs functionalized biomimetic sensing probeA novel ratiometric fluorescence biomimetic sensing probe(BA-LMOFs@MIP)with dual recognition sites based on boric acid-functionalized lanthanide metal-organic framework(supporter and fluorescent core)coupled with molecularly imprinted polymer was constructed via a facile boronate affinity-based controllable oriented surface imprinting strategy.The developed probe achieved efficient and sensitive ratiometric fluorescence detection for trace ribavirin through the antenna effect.In this work,the simple yet efficient imprinting strategy enabled BA-LMOFs@MIP composites to enjoy the significant advantages including high specificity,strong affinity and excellent binding efficiency,which was attributed to the combination of covalent boronate affinity-based recognition sites and non-covalent imprinting sites.Simultaneously,with the introduction of BA-LMOFs as supporter and fluorescent core,BA-LMOFs@MIP demonstrated desirable large surface area,dual fluorescence signal output and superior hydrophilicity.Under optimal detection conditions,BA-LMOFs@MIP-based probe displayed a wide linear range for RBV from 25 ng mL-1 to 1200 ng mL-1 with a detection limit down to 7.6 ng mL-1.The probe was finally applied to RBV determination in egg samples,and the results obtained were consistent with those obtained by HPLC.Therefore,the proposed strategy enriches the construction approach of ratiometric fluorescence probes possessed high sensitivity and selectivity.And the developed probe is expected to provide an efficient,sensitive and specific analysis platform for the monitoring of RBV in complex samples. |
