Highly Emissive Metal-Organic Frameworks for Sensitive and Selective Detection of Nitrofuran and Quinolone Antibiotics

The overuse of antibiotics makes its detection very significant for human health. New facile methods and high-performance sensory materials will be urgently needed for detection of antibiotics. Unfortunately, there are few reports on fluorescence enhancement of antibiotics detection. Herein, based on the modulability of the coordination mode, we proposed two MOFs with different coordination modes based on different metal ions: Zn-MOF ( 1 ) and Cd-MOF ( 2 ). The fluorescence of 1 and 2 can be efficiently and selectively quenched by nitrofuran antibiotics (nitrofurazone, NFZ and furazolidone, FZD) and chloramphenicol (CAP), respectively. Particularly, the matched energy levels between 2 and enrofloxacin (ENR) enables 2 with turn-on sensing for ENR. Moreover, apart from the sensitivity and selectivity, 1 and 2 also have strong recyclable ability, fast response time and anti-interference ability, which make them great potential sensory materials to detect antibiotics.     

基于整体材料搅拌棒固相萃取高效液相色谱联用测定饲料和水样中硝基呋喃类药物残留

利用自制的以聚(乙烯基咪唑-二乙烯基苯)(VIDB)整体材料为涂层的固相萃取搅拌棒(VIDB-SBSE)萃取3种硝基呋喃类药物,然后与高效液相色谱-二极管阵列检测器联用建立了测定饲料和水样品中硝基呋喃类药物残留的方法。详细考察了萃取过程中萃取和解吸时间、样品基质的pH值以及离子强度等实验条件对萃取效率的影响。在最佳条件下,呋喃唑酮的线性范围为0.5~200μg/L,呋喃妥因和呋喃西林的线性范围为0.25~200μg/L,3种目标物的检出限(LO D)(S/N=3)在0.068~0.11μg/L之间,所建方法具有理想的日内和日间重现性(R SD值均小于6%)。在对饲料和实际水样的测定中,不同加标浓度呋喃唑酮、呋喃妥因和呋喃西林的回收率在80.6%~108%之间。研究表明,所建立的方法具有简便、灵敏、环境友好等特点。     

2D Cd-MOF and its mixed-matrix membranes for luminescence sensing antibiotics in various aqueous systems and visible fingerprint identifying

The abuse of antibiotics has brought great harm to the human living environment and health, so it is extremely significant to develop an efficient and simple method to detect trace antibiotic residues in various wastewaters. Herein, a new two-dimensional (2D) Cd-based metal−organic framework (Cd-MOF, namely LCU-111) and its mixed matrix membranes (MMMs) is sifted as luminescence sensors for efficient monitoring antibiotic nitrofurazone (NFZ) in various aqueous systems and applied as visible fingerprint identifying. The LCU-111 has good selectivity, sensibility, reproducibility and anti-interference for luminescent quenching NFZ with low detection limits (LODs) of 0.4567, 0.3649 and 0.8071 ppm in aqueous solution, HEPES biological buffer, and real urban Tuhai River water, respectively. Interestingly, the luminescent test papers and MMMs allow the NFZ sensing easier and more rapid by naked eyes, only with a low LOD of 0.8117 ppm for MMMs sensor. Notably, by combining multiple experiments with density functional theory (DFT) calculations, the photo-induced electron transfer (PET) quenching mechanism is further elucidated. More importantly, potential practical applications of LCU-111 for latent fingerprint visualization provide lifelike evidences for effective identification of individuals, which can be applied in criminal investigation.     

Screening method for the detection of a range of nitrofurans in avian eyes by optical biosensor

An immunobiosensor assay was developed for the multi-residue screening of a range of nitrofuran compounds in avian eyes. A polyclonal antibody which binds at least 5 of the major parent nitrofurans was raised in a rabbit after inoculation with a nitrofuran mimic-protein conjugate. Sample homogenates were extracted into 0.1M hydrochloric acid and subjected to clean-up by solid phase extraction and micro-centrifugation prior to biosensor analysis. Validation data obtained from the analysis of 21 fortified samples has shown that the method has a detection capability (CCβ) of less than 1 ng eye(-1) for nitrofurazone (NFZ). In addition, cross-reactivity data and the analysis of a smaller number of fortified samples have shown that the method will also detect a range of other major parent nitrofurans including furazolidone (FZD), furaltadone (FTD), nitrofurantoin (NFA) and nifursol (NFS). Intra-assay variation (n=10) was calculated at 12.9% and 10.1% at concentrations of 1 ng eye(-1) and 2 ng eye(-1) NFZ respectively. Inter-assay variation (n=3) was determined to be 10.8% and 4.7% at the same NFZ concentrations respectively. The cross-reactivity profile and validation data for the detection of these nitrofurans are presented together with the results obtained following the analysis of a small number of incurred samples using the developed method.     

Determination of β-Agonists in Porcine Urine by Molecularly Imprinted Polymer Based Chemiluminescence

Isoprenaline was used as the template to synthesize a molecularly imprinted polymer that was able to simultaneously recognize ten β-agonists. The simulation showed that the three-dimensional conformation of the template was the main factor responsible for the polymer’s recognition. The polymer particles were coated in the wells of a conventional microplate as the recognition reagent to prepare a chemiluminescence sensor. The light signal was initiated with a highly effective bis(2,4,6-trichlorophenyl) oxalate-H₂O₂-imidazole system. The assay contained only one sample-loading step followed by immediate data acquisition, so one measurement was complete within 12?min. The sensor was used to determine the ten analytes in porcine urine. The results showed that the senor achieved ultrahigh sensitivity, with limits of detection from 2.0 to 7.0?pg/mL, high recoveries from 78.6% to 99.4%, and satisfactory recycle performance up to seven times. This is the first study reporting a molecularly imprinted polymer based microtiter chemiluminescence sensor for the determination of β-agonists.     

Toluene chemiresistor sensor based on nano-porous toluene-imprinted polymer

In this work, the application of molecularly imprinted polymer (MIP) as the recognition element of a chemiresistor sensor was introduced. Toluene-imprinted polymer and non-imprinted polymer (NIP) were synthesized and then mixed with carbon black powder in the presence of melted n-eicosane as the binder agent. The obtained composites were applied for the construction of chemiresistor sensors. The sensor, fabricated with toluene-imprinted polymer, showed a significant response towards toluene. Moreover, the response of the NIP-based (polymer synthesized without solvent) chemiresistor sensor was very small and negligible. The components of the MIP-based sensing composite were found to strongly influence the sensor sensitivity. Response surface experimental design methodology was applied to optimize the important parameters of the proposed sensor. Cross-sensitivity of the MIP-based chemiresistor sensor for different vapours was investigated and a satisfactory result was found for toluene vapour recognition. It was shown that the sensor response to toluene concentration in air was linear in the concentration range of 3.8 to 46.4?ppm. The detection limit and relative standard deviation (for five separate determinations) of the designed sensor were calculated equal to 0.8?ppm and 5.6%, respectively.     

Fabrication of the Enzyme‐less Voltammetric Bilirubin Sensor Based on Sol‐gel Imprinted Polymer

Measuring the serum bilirubin (BR) level is part of the common test for newborns, since high concentrations of bilirubin in the blood can cause brain damage and even death for them. Therefore, achieving a fast, accurate and cost effective method for bilirubin assay in medical diagnosis and Medical management of patients with jaundice, especially neonates, is very important. In this study, an electrochemical sensor was developed to detect low amounts of bilirubin in serum samples. The basis of the work is the BR imprinted polymer synthesis and the use of this polymer as a recognition element in the production of the bilirubin voltammetric sensor. For this purpose, bilirubin imprinted polymer was synthesized using the simple sol gel method and the prepared polymer is characterized by SEM and FT‐IR. In the next step, this polymer was applied to modify the carbon paste electrode and provide a sensitive and selective sensor for the BR molecule. The proposed sensor was able to measure the bilirubin in the concentration range of 1 to 100 μM after optimizing the operating conditions. The limit of detection (LOD) and limit of quantification (LOQ) was calculated 0.75 μM and 2.5 μM respectively. It is also applicable to bilirubin assay in serum samples.     

Surface-enhanced Raman scattering sensor for theophylline determination by molecular imprinting on silver nanoparticles

A surface-enhanced Raman scattering (SERS)-based sensor for the determination of theophylline (THO) has been developed by imprinting the target molecules on the surface of silver nanoparticles. The desired recognition sites are generated after template removal and homogeneous distribution on the silver nanoparticles that have been incorporated within polymer matrix by the in situ reduction of theophylline-silver complexes, providing molecular recognition ability and SERS active surfaces. The theophylline molecules, complementary to the shape, size, and functionality of the recognition cavities, can selectively bind to the recognition sites at the surface of silver nanoparticles driven by the formation of hydrogen bonding and surface coordination. It has been demonstrated that the SERS signals of the theophylline molecules captured on the surface of the silver nanoparticles have a good reproducibility and a dose-response relationship to the target analytes, showing the potential for reliable identification and quantification of the bioactive compound. The molecular imprinting-based SERS sensor, like antibodies or enzymes, also possesses the ability to distinguish theophylline from the closely related structure caffeine due to the variations of molecular size and shape as well as the different affinity to silver ions.     

Fluorescence Ratiometric Antibiotic Detection with a Single Lanthanide Metal-Organic Framework

Antibiotic residues are currently an increasing threat for human health and the ecosystem, and specific and rapid real-time sensing of antibiotics is a big challenge. To realize specific sensing by rapid fluorescent sensors, a lanthanide metal-organic framework (MOF) containing dual emissive centers has been developed with high sensing selectivity and sensitivity. Owing to the self-calibration ability, the dual-center Tb-MOF exhibits higher selectivity towards furazolidone (FZD) and nitrofural (NZF) among the reported MOF sensors. Additionally, the corresponding ratiometric detection mode also realized specific sensing of other tested antibiotics. Besides, the single-Tb³⁺-based dual-emission MOF in this work is expected to support the development of fluorescent sensors with high sensitivity and selectivity for environmental safety purposes.     

Determination of nitrofurans in animal feeds by liquid chromatography-UV photodiode array detection and liquid chromatography-ionspray tandem mass spectrometry

Within the EU, the use of nitrofurans is prohibited in food production animals. For this reason detection of these compounds in feedingstuffs, at whatever limit, constitutes an offence under EU legislation. This detection generally involves the use of analytical methods with limits of quantification lowers than 1 mg kg(-1). These procedures are unsuitable for the detection and confirmation of trace amounts of nitrofurans in feedingstuffs due to contamination. It is well known that very low concentrations of these compounds can be the source of residues of nitrofuran metabolites in meat and other edible products obtained from animals consuming the contaminated feed. The present multi-compound method was capable of measuring very low concentrations of nitrofurantoin (NFT), nitrofurazone (NFZ), furazolidone (FZD) and furaltadone (FTD) in animal feed using nifuroxazide (NXZ) as internal standard. Following ethyl acetate extraction at mild alkaline conditions and purification on NH2 column, the nitrofurans are determined using liquid chromatography with photodiode-array detection (LC-DAD). It was observed a CCalpha ranged from 50 to 100 microg kg(-1). The liquid chromatography-tandem mass spectrometric (LC-MS/MS) procedure was used to confirm the identity of the suspected presence of any of the nitrofuran compounds.     

High Selective Parathion Voltammetric Sensor Development by Using an Acrylic Based Molecularly Imprinted Polymer‐Carbon Paste Electrode

The design and construction of an extra high selective voltammetric sensor for parathion by using a molecularly imprinted polymer (MIP) as recognition element was introduced. A parathion selective MIP and a nonimprinted polymer (NIP) were synthesized and then incorporated in the carbon paste electrode. The MIP‐CP electrode showed very high recognition ability in comparison to NIP‐CP. It was shown that electrode washing after parathion extraction, led to enhanced selectivity. Some parameters affecting the sensor response were optimized and then the calibration curve was plotted. A dynamic linear range of 1.7–900 nM was obtained. The detection limit of the sensor was calculated as 0.5 nM. This sensor was used successfully for parathion determination in real samples such as ground water and vegetables.     

A piezoelectric biomimetic sensor for aminopyrine with a molecularly imprinted polymer coating

A molecularly imprinted polymer for aminopyrine was synthesized using methacrylic acid as functional monomer. The polymer was employed as the recognition element of a piezoelectric bulk acoustic wave biomimetic sensor for aminopyrine. Influencing factors were investigated in detail and optimized. This sensor exhibited high selectivity and sensitivity to aminopyrine. The response range of the sensor was between 5.0 x 10(-8) and 1.0 x 10(-4) M with a detection limit of 2.5 x 10(-8) M in the aqueous system. Scatchard analysis with UV spectrophotometry showed that the same class of binding sites was formed in the molecularly imprinted polymer in the studied concentration range, and the dissociation constant and the apparent maximum number of these binding sites were estimated to be 2.29 mM and 165.0 mumol g-1 dry polymer, respectively. Impedance analysis was employed to verify the imprinting effect and lack of variation in the viscoelasticity of the polymer coating during detection.     

Chemiluminescent flow-through sensor for 1,10-phenanthroline based on the combination of molecular imprinting and chemiluminescence.

A functional polymer for the catalysis of the chemiluminescent reaction and molecular recognition ability of 1,10-phenanthroline was prepared based on the molecular imprinting method. The structural and catalytic roles of transition metal ion interactions were applied in the material design. A ternary complex, 4-vinylpyridine-Cu(II)-1,10-phenanthroline (2:1:1), was synthesized and used as a functional monomer. The ligand 1,10-phenanthroline in the ternary complex was the template used to form the molecularly imprinted polymer. Another monomer, styrene, and the cross-linking reagent divinylbenzene were copolymerized with the ternary complex. The polymer containing the ternary complex is an efficient catalyst for the decomposition of hydrogen peroxide. During the hydrogen peroxide decomposition, superoxide radical ion is formed, which reacts with 1,10-phenanthroline and gives a chemiluminescent emission. The 1,10-phenanthroline was destroyed during the chemiluminescent reaction, leaving a cavity and copper binding sites for another 1,10-phenanthroline molecule. The prepared polymer particles were packed into a glass tube and developed as a molecular recognition chemiluminescent flow-through sensor for 1,10-phenanthroline. The sensitivity and selectivity of the sensor were tested.     

A linear supramolecular polymer based on host-guest recognition and metal-ligand coordination

A linear main-chain supramolecular polymer was constructed in aqueous solution via γ-CD host recognition with coumarin unit as well as metalligand coordination between terpyridine unit and Zn²⁺. Besides, the self-assembly behavior and morphological property of this supramolecular polymer system were characterized by DLS and TEM experiments.     

Enantioselective sensor based on microgravimetric quartz crystal microbalance with molecularly imprinted polymer film

We report a novel quartz crystal microbalance sensor that provides enantioselectivity to dansylphenylalanine enantiomers by using a molecularly imprinted polymer film as a recognition element. The polymeric recognition thin film, imprinted with chiral dansyl-L-phenylalanine, was immobilised on a gold electrode modified with a photoactive precursor monolayer via a self-assembly process using photopolymerization. The fabricated sensor was able to discriminate between L- and D-dansylphenylalanine enantiomers in solution owing to the enantioselectivity of the imprinted sites. The enantiomeric composition of L- and D-enantiomeric mixtures could be quantitatively determined by the fabricated sensor. The detection limit is 5 micrograms mL-1 with a response range of 5-500 micrograms mL-1 at pH 10.0. The influence of the template concentration on the sensitivity and selectivity of the synthesised polymer membranes was investigated and optimised. The surface characteristics of the polymer coating were studied by varying the pH value of the buffer solution, and a convenient regeneration process was proposed to increase the reproducibility and reusability of the sensor by flushing with pH 2.0 buffer. The selectivity and recognition mechanism of the imprinted polymer film were studied with compounds that are structurally related to the template. The method presented in this work provides a novel means of preparing highly selective and sensitive chemical sensors via self-assembly and molecularly imprinting techniques.     

酰腙键聚合物凝胶的制备及其在硝基呋喃类药物分析中的应用

以1,3,5-苯三甲酰肼和间苯二甲醛为有机单体,利用席夫碱反应原理和酰腙共价键为交联点,通过一步交联聚合法研制了一种新型酰腙键聚合物凝胶。采用扫描电子显微镜、红外光谱、固体核磁和热重分析对所制备的聚合物凝胶进行结构和形貌表征,结果表明材料具有良好的物化性能。将其作为固相萃取吸附剂,结合高效液相色谱-二极管阵列检测器检测,建立了饲料中4种硝基呋喃类药物的分析方法。通过单因素实验,系统考察了吸附剂用量、上样体积、洗脱溶剂和洗脱体积对方法回收率的影响。在最优实验条件下,呋喃它酮（FTD）、呋喃西林（NFZ）、呋喃妥因（NFT）和呋喃唑酮（FZD）在1.0～200μg/L范围内线性关系良好,相关系数（r）均大于0.9990,方法的检出限以信噪比（S/N=3）计算为0.1～0.5μg/L,定量限（S/N=10）为1.0～5.0μg/L,在3个浓度水平（10、50和100μg/L）加标下样品的回收率在78.5%～96.8%之间,相对标准偏差（RSD）为2.1%～9.3%。该方法的检出限低、灵敏高,可用于饲料样品中硝基呋喃类药物的灵敏准确分析。     

基于金属离子交换的有机金属凝胶用于检测抗生素与硝基芳香族化合物

废水中有机化合物的快速检测一直是一个重要的问题。采用离子交换法制备了具有荧光特性的铽基金属有机凝胶MOG（Tb）。研究表明,即使存在其他有机化合物,微量的呋喃唑酮（FZD）、甲硝唑（MDZ）、2,4-二硝基甲苯（2,4-DNT）和4-硝基苯酚（4-NP）也能有效猝灭MOG（Tb）的荧光发射,证明MOG（Tb）干凝胶作为一种化学传感器可以有效检测抗生素（FZD、MDZ）和硝基芳香族化合物（2,4-DNT、4-NP）。有趣的是,青霉素钾（PCLP）却能增强MOG（Tb）的荧光。此外,还进行了MOG（Tb）干凝胶的可回收性和水稳定性试验,并得到了较为满意的结果。     

基于分子印迹技术的丙溴磷压电石英晶体微天平研制

介绍了一种用于检测丙溴磷农药的分子印迹压电生物传感器的构建方法。采用沉淀聚合法合成了农药丙溴磷的分子印迹聚合物,将其固定于石英晶体微天平电极表面构建传感器;采用环境扫描电镜以及原子力显微镜对聚合物形貌、传感器电极表面形貌特征进行分析,并利用传感器对丙溴磷农药进行检测分析,其质量浓度在10~1000 ng/mL范围内,传感器频率改变与丙溴磷浓度之间的响应呈线性关系,线性方程为y=0.139ρ+2.26(r=0.9984)。结果表明,构建的分子印迹压电生物传感器能够对农药进行初步检测,具有较高的灵敏性和较好的特异识别能力。     

Development of trichloroacetic acid sensor based on molecularly imprinted polymer membrane for the screening of complex mixture of haloacetic acids in drinking water

This work shows developing conductometric sensor based on molecularly imprinted polymer (MIP) for the screening of complex mixture of haloacetic acids (HAAs) in drinking water. The recognition of the HAAs was achieved by trichloroacetic acid (TCAA)-imprinted polymers synthesised from the copolymerization of 4-vinylpyridine (4-VPD) and ethylene glycol dimethacrylate (EDMA) in the presence of the TCAA template in acetonitrile, either by bulk polymerization (BP) method or by a multi-step swelling polymerization (MSP) method. TCAA-imprinted polymer of both methods was tested for re-binding with the template and its analogs. It was found that these polymers could bind selectively to the template molecule and HAA derivatives. HAA measurements were carried out by the application of the polyvinyl chloride membrane fabricated with TCAA-imprinted polymer on conductometric sensors. The technological parameters (operating frequency, membrane composition, ionic strength and medium pH) for the sensors were identified and optimised in respect to the response to TCAA, using sensor fabricating with BP-based MIP as a model. The selectivity of the sensors constructed with MIPs made by either that of the two imprinting methods was also investigated, which the influence of the method of imprinting on the binding strength and selectivity of the recognition element embedded in sensor was observed. The sensors showed high sensitivity and selectivity for the response toward TCAA, the sensor modified with MSP-based MIP being better. In addition, the sensors, particularly when was constructed with MSP-based MIP exhibited good cross-reactivities with a wide range of HAAs, which is useful for the screening of the group of HAA usually present in chlorinated water in complex mixtures. Thus, the sensor modified with MSP-based MIP was chosen for analytical application. The calibration of this sensor was determined, showing the good linear graphs (R²>0.970) for HAAs over the concentration range of 25-1000 μg/l and the detection limit of each HAA in the range 0.2-5.0 μg/l. Moreover, the results in real analysis of the sensor indicate the simplicity and reliability of the method. The present work demonstrated that the sensor based on TCAA-imprinted polymer is a fast and sensitive screening method of HAAs in drinking water.     

A Water-Gated Organic Thin-Film Transistor for Glyphosate Detection: A Comparative Study with Fluorescence Sensing

This work reports the design of a highly sensitive solid-state sensor device based on a water-gated organic thin-film transistor (WG-OTFT) for the selective detection of herbicide glyphosate (GlyP) in water. A competitive assay among carboxylate-functionalized polythiophene, Cu²⁺, and GlyP was employed as a sensing mechanism. Molecular recognition phenomena and electrical double layer (EDL) (at the polymer/water interface) originated from the field-effect worked cooperatively to amplify the sensitivity for GlyP. The limit of detection of WG-OTFT (0.26 ppm) was lower than that of a fluorescence sensor chip (0.95 ppm) which is the conventional sensing method. In contrast to the previously reported insulated molecular wires to block interchain interactions, molecular aggregates under the field-effect has shown to be effective for amplification of sensitivity through “intra”- and “inter”-molecular wire effects. The opposite strategy in this study could pave the way for fully utilizing the sensing properties of polymer-based solid-state sensor devices.