New sensing materials of molecularly-imprinted polymers for the selective recognition of Chlortetracycline

Tetracycline antibiotics and NH4+ detection by Zn-organic framework fluorescent probe

A fluorescent probe based on single metal-organic framework material without additional fluorophores and active sites can significantly improve the stability of the probe for detection, and has very important application value in environmental analysis and detection. In this paper, a simple and rapid fluorescence detection method was established with Zn-MOF, which realized the highly sensitive detection of tetracycline antibiotics and NH₄⁺ in water. The prepared Zn-MOF has abundant pores and can exist stably in water. When tetracycline antibiotics are present in Zn-MOF aqueous solution, based on the unique coordination ability between Zn and N, tetracycline antibiotics rich in N will be adsorbed into the pore canals of MOF, and aggregation-induced luminescence will occur. The original non-fluorescent Zn-MOF will immediately produce yellow fluorescence, realizing the detection of tetracycline antibiotics in water, with the limit of detection reaching 0.017 μM in a linear range of 0.02-13 μM. Zn-MOF is further used for the detection of tetracycline antibiotics in actual samples of milk and honey. Oxytetracycline (OTC) with the best fluorescence response of tetracycline antibiotics was coated on Zn-MOF to synthesize OTC@Zn-MOF fluorescent probe. NH₄⁺ will replace the original ligand of Zn-MOF, which will disintegrate MOF and release OTC, resulting in a fluorescence decrease. Therefore, NH₄⁺ can be detected with low limit of detection (0.038 μM) in a linear range of 0 to 3 mM. The probe is expected to be able to detect ammonia in the environment.

Recent application of molecular imprinting technique in food safety

Due to the extensive use of chemical substances such as pesticides, antibiotics and food additives, food safety issues have gradually attracted people's attention. The extensive use of these chemicals seriously damages human health. In order to detect trace chemical residues in food, researchers have to find several simple, economical and effective tools for qualitative and quantitative analysis. As a kind of material that specifically and selectively recognize template molecules from real samples, molecular imprinting technique (MIT) has widely applied in food samples analysis. This article mainly reviews the application of molecularly imprinted polymer (MIP) in the detection of chemical residues from food in the past five years. Some recent and novel methods for fabrication of MIP are reviewed. Their application of sample pretreatment, sensors, etc. in food analysis is reviewed. The application of molecular imprinting in chromatographic stationary phase is referred. Additionally, the challenges faced by MIP are discussed.

Recent Progress of Imprinted Nanomaterials in Analytical Chemistry

Molecularly imprinted polymers (MIPs) are a type of tailor-made materials that have ability to selectively recognize the target compound/s. MIPs have gained significant research interest in solid-phase extraction, catalysis, and sensor applications due to their unique properties such as low cost, robustness, and high selectivity. In addition, MIPs can be prepared as composite nanomaterials using nanoparticles, multiwalled carbon nanotubes (MWCNTs), nanorods, quantum dots (QDs), graphene, and clays. This review paper aims to demonstrate and highlight the recent progress of the applications of imprinted nanocomposite materials in analytical chemistry.

Enhanced photocatalytic degradation of doxycycline using a magnetic polymer-ZnO composite

A novel magnetic polymer-ZnO composite was prepared by incorporating Fe₃O₄ and ZnO nano-particles in the structure of an adsorbent polymer. Precipitation polymerization was used for synthesizing the adsorbent polymer and its efficiency for extracting doxycycline from aqueous solution was optimized according to several parameters including time, pH and amount of polymer. Results showed the highest extraction efficiency at neutral pH of the doxycycline solution in 20 min, and the capacity of the polymer was about 20 mg/g. The magnetic property of a material is important for fast and facile separation of composite particles after each use. Magnetic polymer-ZnO composite was synthesized by adding Fe₃O₄ and ZnO nano-particles to the polymerization mixture in order to take advantage of both sorption and photocatalytic degradation mechanisms. The obtained composite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy equipped with wavelength dispersive X-ray spectroscopy and used for enhanced photocatalytic degradation of doxycycline in aqueous solution. Results showed 76.5% degradation of doxycycline in 6 hours which was significantly higher than the degradation observed by an equivalent amount of ZnO nano-particles. Photocatalytic degradation of doxycycline fitted the pseudo first order kinetic model with a rate constant of 4 × 10^-3 μg mL^-1 min^-1.

Highly luminescent nitrogen-doped carbon dots for simultaneous determination of chlortetracycline and sulfasalazine

Here, we have presented a green and facile strategy to fabricate nitrogen-doped carbon dots (N-CDs) and their applications for determination of chlortetracycline (CTC) and sulfasalazine (SSZ). The fluorescent N-CDs, prepared by one-step hydrothermal reaction of citric acid and l-arginine, manifested numerous excellent features containing strong blue fluorescence, good water-solubility, narrow size distribution, and a high fluorescence quantum yield (QY) of 38.8%. Based on the fluorescence quenching effects, the as-synthesized N-CDs as a fluorescent nanosensor exhibited superior analytical performances for quantifying CTC and SSZ. The linear range for CTC was calculated to be from 0.85 to 20.38 μg ml^-1 with a low detection limit of 0.078 μg ml^-1 . Meanwhile, the linear range for SSZ was estimated to be from 0.34 to 6.76 μg ml^-1 with a low detection limit of 0.032 μg ml^-1 . Therefore, the N-CDs hold admirable application potential for constructing a fluorescent sensor for pharmaceutical analysis.

Novel potentiometric sensors for the determination of the dinotefuran insecticide residue levels in cucumber and soil samples

Five new potentiometric membrane sensors for the determination of the dinotefuran levels in cucumber and soil samples have been developed. Four of these sensors were based on a newly designed molecularly imprinted polymer (MIP) material consisting of acrylamide or methacrylic acid as a functional monomer in a plasticized PVC (polyvinyl chloride) membrane before and after elution of the template. A fifth sensor, a carboxylated PVC-based sensor plasticized with dioctyl phthalate, was also prepared and tested. Sensor 1 (acrylamide washed) and sensor 3 (methacrylic acid washed) exhibited significantly enhanced responses towards dinotefuran over the concentration range of 10^-7-10^-2molL^-1. The limit of detection (LOD) for both sensors was 0.35µgL^-1. The response was near-Nernstian, with average slopes of 66.3 and 50.8mV/decade for sensors 1 and 3 respectively. Sensors 2 (acrylamide non-washed), 4 (methacrylic acid non-washed) and 5 (carboxylated-PVC) exhibited non-Nernstian responses over the concentration range of 10^-7-10^-3molL^-1, with LODs of 10.07, 6.90, and 4.30µgL^-1, respectively, as well as average slopes of 39.1, 27.2 and 33mV/decade, respectively. The application of the proposed sensors to the determination of the dinotefuran levels in spiked soil and cucumber samples was demonstrated. The average recoveries from the cucumber samples were from 7.93% to 106.43%, with a standard deviation of less than 13.73%, and recoveries from soil samples were from 97.46% to 108.71%, with a standard deviation of less than 10.66%. The sensors were applied successfully to the determination of the dinotefuran residue, its rate of disappearance and its half-life in cucumbers in soil in which a safety pre-harvest interval for dinotefuran was suggested.

Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers

Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Bio-mimetic sensors based on molecularly imprinted membranes

An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. By means of this technology, selective molecular recognition sites are introduced in a polymer, thus conferring it bio-mimetic properties. The potential applications of these systems include affinity separations, medical diagnostics, drug delivery, catalysis, etc. Recently, bio-sensing systems using molecularly imprinted membranes, a special form of imprinted polymers, have received the attention of scientists in various fields. In these systems imprinted membranes are used as bio-mimetic recognition elements which are integrated with a transducer component. The direct and rapid determination of an interaction between the recognition element and the target analyte (template) was an encouraging factor for the development of such systems as alternatives to traditional bio-assay methods. Due to their high stability, sensitivity and specificity, bio-mimetic sensors-based membranes are used for environmental, food, and clinical uses. This review deals with the development of molecularly imprinted polymers and their different preparation methods. Referring to the last decades, the application of these membranes as bio-mimetic sensor devices will be also reported.

Host-Tailored Sensors for Leucomalachite Green Potentiometric Measurements

A new biomimetic sensor for leucomalachite green host-guest interactions and potentiometric transduction is presented. The artificial host was imprinted in methacrylic acid or acrylamido-2-methyl-1-propanesulfonic acid-based polymers. Molecularly imprinted particles were dispersed in 2-nitrophenyloctyl ether and trapped in poly(vinyl chloride). The potentiometric sensors exhibited a near-Nernstianresponse in steady state evaluations, with slopes and detection limits ranging from 45.8 to 81.2 mVdecade-1and 0.28 to 1.01 μg mL-1, respectively. They were independent from the pH of test solutions within 3 to 5. Good selectivity was observed towards drugs that may contaminate water near fish cultures, such as oxycycline, doxycycline, enrofloxacin, trimethoprim, creatinine, chloramphenicol, and dopamine. The sensors were successfully applied to field monitoring of leucomalachite green in river samples. The method offered the advantages of simplicity, accuracy, applicability to colored and turbid samples, and automation feasibility.

Molecularly imprinted membranes

Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40-50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that molecular imprinted membranes (i.e., polymer thin films) that show recognition properties at molecular level of the template molecule are used in their formation. Different procedures and potential application in separation processes and catalysis are reported. The influences of different parameters on the discrimination abilities are also discussed.

Application of molecularly imprinted polymers in food analysis: clean-up and chromatographic improvements

Several natural and synthetic substances have been monitored in analytical laboratories worldwide to ensure food safety. Multiple residue detection (i.e., detection of multiple analytes in a single sample or matrix) is a main weakness of existing analytical methods, when fast and reliable results are required. Multianalyte approaches may save time and money in the food industry, and more importantly, they allow the quick release of food products into the marketplace. In addition, multianalyte approaches notably decrease the time required between sampling and analysis to meet legal requirements. However, to achieve analytical success, it is necessary to develop thorough clean-up procedures to extract analytes from the matrix. In addition, good chromatographic separation methods are also necessary to distinguish closely related analytes. Molecular imprinting technology (MIT) is an emerging, powerful tool for sample extraction and chromatography. First used for solid-phase extraction, molecularly imprinted polymers (MIPs) are also effective chromatographic phases for the separation of isomers and structurally related molecules. In recent years, a number of analytical methods utilising MIT have been applied for the analysis of residues in food, and existing methodologies have been improved. This review article describes the latest applications of MIT in the development of methodologies to monitor the presence of residues of veterinary products in foodstuff.