| The overuse or abuse of tetracyclines?TCs?in animal-derived food has been caused devastating effects on the environment and vital biological processes involved with the decoding of genetic information and protein synthesis and induce undesirable influences on human health by increasing the risk of certain infections.Most of traditional methods for TCs detection are time-consuming,expensive,sophisticate and skilled personnel needed,and these disadvantages limit their applications in routine analysis.Therefore,it is indispensable to establish a simple,efficient,sensitive and universal method for the detection of TCs.Fluorescent analysis method is considered as a simple,sensitive,easy-to-operate and low-cost method.Metal-organic frameworks?MOFs?are widely explored owing to their intriguing spectral characteristics e.g.,large surface area,tunable pore size,excellent thermal stability,availability of in-pore functionality and outer-surface modification,which has great potential for TCs detection.However,the application of MOFs for TCs detection has some merits of lack of specificity,low sensitivity and narrow application ranges.The paper focused on the typical TCs?TET,DOX,OTC and CTC?residues in animal-drived foods,designing a series of functional MOFs fluorescence sensors according to the characteristics of TCs to sensitively detect TCs.And the specific mechanism between TCs and MOFs was investigated,aiming to provide technical and theoretical basis for the establishment and improvement of food safety supervision system.The main research contents and results are as follows:?1?3D functional Zr-MOF fluorescence sensor for TCs detectionFive functional Zr-MOF of Ui O-66-X?X=NH2,OH,COOH,Br and NO2?were synthesized by solvothermal method.The best fluorescent MOFs-Ui O-66-NH2 was selected as a probe based on the fluorescence signal.Constructing detection methods,exploring detection mechanisms and evaluating the feasibility of Ui O-66-NH2 nanoprobes for the detection of TCs in animal-derived foods.The results showed that:the order of the FL intensities of five functionalized MOFs with different functional groups is:Ui O-66-NH2>Ui O-66-COOH>Ui O-66-OH>Ui O-66-NO2>Ui O-66-Br.Ui O-66-NH2 has a regular octahedron structure with an average particle size of 260 nm.Ui O-66-NH2 has a stable fluorescence signal under acidic conditions and has a strong resistance to photobleaching.The–NH2 of Ui O-66-NH2 could transfer electrons to TCs and cooperated with inner-filter effect?IFE?,resulting in fluorescence quenching.The optimal detection conditions were as follows:the probe concentration was 40.0 mg/L,p H was 6.0,the incubation time was 10 min and the temperature was room temperature.The detection limits?LODs?for TCs?TET,DOX and OTC?are 68.6,78.4 and 124.9 nmol/L,respectively,which were much lower than those of the maximum residue limits published by international criteria.TCs could be selectively detected in the presence of common interfering substances.The detection of TCs residues in animal-derived foods?fish,chicken,pork,eggs,and milk?with this sensor had acceptable recoveries?95.24-100.46%?,indicating that the Ui O-66-NH2 sensor has potential applicability to TCs Detection in animal-derived foods.This method has the advantages of easy synthesis of materials,low cost and simple operation,but it still lacks specificity and sensitivity.?2?2D amino functionalized Al-MOF fluorescence sensor for TCs detectionFive different metal ions?Zr4+,Al3+,Cr3+,Ti4+ and Fe3+?were selected as the metal source and the 2-aminoterephthalic acid?NH2-BDC?as organic ligand to synthesize MOFs by one step hydrothermal/solvent methods.The best fluorescent MOFs-NH2-MIL-53?Al?was selected based on the fluorescence signal and fluorescence lifetime indicators.The detection performence and mechanism of the NH2-MIL-53?Al?nanoprobe were investigated.NH2-MIL-53?Al?nanoprobe was used to evaluate the feasibility of detecting TCs in animal-derived foods.The results showed that:The FL intensity of five MOFs was sorted as follows:NH2-MIL-53?Al?>NH2-MIL-53?Ti?>Ui O-66?Zr?-NH2>NH2-MIL-101?Cr?>NH2-MIL-88B?Fe?.NH2-MIL-53?Al?has a shortest average fluorescence lifetime,indicating its lowest ligand-to-metal charge transfer efficiency and thus leads to a highest FL intensity.Compared with Ui O-66-NH2,NH2-MIL-53?Al?had a wider p H range?6.0-10.0?,faster response?25 s?and great anti-interference.LODs of TCs?DOX:40.36 nmol/L;TET:26.16nmol/L;OTC:62.05 nmol/L?is lower than Ui O-66-NH2.NH2-MIL-53?Al?nanosensor can quantitatively detect TCs in raw milk samples with satisfactory recoveries?85.15-112.13%?,which showed potential advantages in comparison with HPLC?P>0.05?.The present work may provide a novel and practical method for determination of TCs in food matrix.This method still lacks of sensitivity.?3?Interface engineering of zeolite imidazolate framework-8 on 2D Al-MOF nanoplates for sensing TCs nanoplates for sensing TCsOn the basis of two-dimensional NH2-MIL-53?Al?research,zeolite imidazolate framework-8?ZIF-8?was anchored on two-dimensional?2D?amino-functionalized Al-metal organic framework?NH2-MIL-53?Al??nanoplates to construct a dual metal-organic frameworks smart platform?ZIF-8/NH2-MIL-53?Al??so as to realize the pre-concentration of TCs and improve the detection sensitivity.The pre-concentration effect of the resultant ZIF-8/NH2-MIL-53?Al?nanohybrid toward TCs was studied by batch experiment,as well as detection performances were systematically investigated by FL titration experiments.ZIF-8/NH2-MIL-53?Al?nanosensor was used to evaluate the feasibility of detecting TCs in animal-derived foods.The results showed that:ZIF-8 nanoparticles anchored on 2D nanoplates having a smaller size and larger specific surface area boosted the adsorption capabilities(561,533,526 and 578 mg g-1 for doxycycline?DOX?,tetracycline?TET?,oxytetracycline?OTC?and chlortetracycline?CTC?,respectively).Notably,the pyridine N of ZIF-8 cooperated with the abundant–NH2 on the surface of NH2-MIL-53?Al?exhibited high affinity toward TCs,remarkably enhancing the sensitivity by facilitating the photo-induced electron transfer and the inner-filter effect.The LOD values(1.2?g L-1 for TET,DOX,OTC and 2.2?g L-1 for CTC,respectively)were at least 10-fold lower than those of NH2-MIL-53?Al?and were comparable or superior to those of reported sensors.The detection of TCs in animal-derived foods?pork,fish and milk?using the ZIF-8/NH2-MIL-53?Al?sensor presented satisfactory reliabilities?92.84-103.22%?.In addition,ZIF-8/NH2-MIL-53?Al?nanocomposite had good stability,wide p H?4.0-10.0?adaptability,strong anti-interference ability and good reusability,making it an ideal fluorescence nanosensor for detecting TCs.?4?3D hierarchical dual-metal-organic framework heterostructure for sensing TCsOn the basis of ZIF-8/NH2-MIL-53?Al?,the structure of the MOF-on-MOF composite material is regulated,so as to further improve the enrichment and preconcentration of the target TCs,thus realize the ultra-sensitive detection of TCs.3D hierarchical dual-metal-organic framework heterostructure,Al-MOF@Mo/Zn-MOF,was developed by integrating amino-functionalized Al-metal-organic framework?Al-MOF?with bimetallic imidazolate framework?Mo/Zn-MOF?via an internal extended growth method.The pre-concentration effect of the materials was explored through batch experiment,and the fluorescence detection performance and detection mechanism of the materials were systematically investigated by FL titration experiments.Al-MOF@Mo/Zn-MOF nanosensor was used to evaluate the feasibility of detecting TCs in animal-derived foods.The results showed that:the functional Al-MOF@Mo/Zn-MOF heterostructure exhibited a flower-like hierarchical structure with an average size of?1?m and was covered with 2D nanosheets.Al-MOF@Mo/Zn-MOF displayed a typically reversible type-I adsorption isotherm.A surface area of about 1830 m2 g-1,the total volume of pores of 0.650 cm3 g-1 and narrow pore diameter distribution of 1.61 nm were verified as well.The as-prepared Al-MOF@Mo/Zn-MOF nanohybrid exhibited extraordinary adsorption capabilities of1673.02,1629.07,1564.94 and 1782.99 mg g-1 for DOX,TET,OTC and CTC.The superior adsorption ability significantly enhanced the pre-concentration of Al-MOF@Mo/Zn-MOF,making the detection of TCs more sensitive.In detail,the solubility partition coefficients of TCs in MOF/water system(KMOF/water)were calculated to be 8822,8612,5691 and 13504 for DOX,TET,OTC and CTC.The large KMOF/water values evidenced the TCs tending to preferentially access the pores of Al-MOF@Mo/Zn-MOF,validating the preconcentration effect.Therefore,the superior adsorption ability of the 3D hierarchical Al-MOF@Mo/Zn-MOF heterostructure nanoflower could significantly enhance the pre-concentration effect and further highlight the sensitivity for TCs detection.The Al-MOF@Mo/Zn-MOF revealed excellent anti-interference performances and ultra-low LODs of 0.56,0.53,0.58 and 0.86 n M for DOX,TET,OTC and CTC.These acquisition LOD values were two orders of magnitude lower than that of pristine amino-functionalized Al-MOF,and comparable or even superior to previous fluorescence-based sensors.Satisfactory recoveries of 87.07-116.44%and RSDs of 0.22-2.30%were achieved to detect TCs in real water and food samples.These excellent sensing properties render the 3D hierarchical Al-MOF@Mo/Zn-MOF heterostructure promising for ultrasensitive detection of TCs in practical applications. |
PDF Full Text Request