Upconversion particle@Fe3O4@molecularly imprinted polymer with controllable shell thickness as high-performance fluorescent probe for sensing quinolones

Cyclodextrin-based ternary supramolecular deep eutectic solvents for efficient extraction and analysis of trace quinolones and sulfonamides in wastewater by adjusting pH

BACKGROUND

Antibiotics residues can accelerate the growth of drug-resistant bacteria and harm the ecological environment. Under the effect of enrichment and biomagnification, the emergence of drug-resistant pathogenic bacteria may eventually lead to humans being ineffective to drugs in the face of bacterial or fungal disease infections in the future. It is urgent to develop an efficient separation medium and analytical method for simultaneous extraction and determination of antibiotics in the water environment.

RESULTS

This work doped 2,6-Di-O-methyl-β-cyclodextrin, randomly methyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin with thymol:fatty acid respectively to construct non-covalent interaction-dominated pH-responsive ternary supramolecular deep eutectic solvents (SUPRADESs), which can undergo a hydrophilic/hydrophobic transition with aqueous phase to achieve an efficient microextraction. Semi-empirical method illustrated that SUPRADESs have a wide range of hydrogen bond receptor sites. We developed a SUPRADES-based analytical method combined with liquid chromatography-triple quadrupole mass spectrometry for the extraction and determination of trace quinolones and sulfonamides in wastewater. The overall limits of detection of the method were 0.0021-0.0334 ng mL-1 and the limits of quantification were 0.0073-0.1114 ng mL-1. The linearity maintained good in the spiked level of 0.01-100 ng mL-1 (R2 > 0.99). The overall enrichment factors of the method were 157-201 with lower standard deviations (≤8.7).

SIGNIFICANCE

The method gave an extraction recovery of 70.1-115.3 % for 28 antibiotics in livestock farming wastewater samples from Zhejiang, China, at trace levels (minimum 0.5 ng mL-1). The results demonstrated that inducing the phase transition between SUPRADES and aqueous phase by adjusting pH for extraction is a novel and efficient pretreatment strategy. To our knowledge, this is the first application of cyclodextrin-based ternary SUPRADESs with pH-responsive reversible hydrophobicity-hydrophilicity transition behavior in wastewater analysis.

Recent advances in rare earth ion-doped upconversion nanomaterials: From design to their applications in food safety analysis

The misuse of chemicals in agricultural systems and food production leads to an increase in contaminants in food, which ultimately has adverse effects on human health. This situation has prompted a demand for sophisticated detection technologies with rapid and sensitive features, as concerns over food safety and quality have grown around the globe. The rare earth ion-doped upconversion nanoparticle (UCNP)-based sensor has emerged as an innovative and promising approach for detecting and analyzing food contaminants due to its superior photophysical properties, including low autofluorescence background, deep penetration of light, low toxicity, and minimal photodamage to the biological samples. The aim of this review was to discuss an outline of the applications of UCNPs to detect contaminants in food matrices, with particular attention on the determination of heavy metals, pesticides, pathogenic bacteria, mycotoxins, and antibiotics. The review briefly discusses the mechanism of upconversion (UC) luminescence, the synthesis, modification, functionality of UCNPs, as well as the detection principles for the design of UC biosensors. Furthermore, because current UCNP research on food safety detection is still at an early stage, this review identifies several bottlenecks that must be overcome in UCNPs and discusses the future prospects for its application in the field of food analysis.

Nanomaterial-based fluorescent biosensors for the detection of antibiotics in foodstuffs: A review

Antibiotics are widely used as bacteriostatic or bactericidal agents against various microbial infections in humans and animals. The excessive use of antibiotics has led to an accumulation of their residues in food products, which ultimately poses a threat to human health. In light of the shortcomings of conventional methods for antibiotic detection (primarily cost, proficiency, and time-consuming procedures), the development of robust, accurate, on-site, and sensitive technologies for antibiotic detection in foodstuffs is important. Nanomaterials with amazing optical properties are promising materials for developing the next generation of fluorescent sensors. In this article, advances in detecting antibiotics in food products are discussed with respect to their sensing applications, with a focus on fluorescent nanomaterials such as metallic nanoparticles, upconversion nanoparticles, quantum dots, carbon-based nanomaterials, and metal-organic frameworks. Furthermore, their performance is evaluated to promote the continuation of technical advances.

A Novel Sulfonamide, Molecularly Imprinted, Upconversion Fluorescence Probe Prepared by Pickering Emulsion Polymerization and Its Adsorption and Optical Sensing Performance

A novel, molecularly imprinted, upconversion fluorescence probe (UCNP@MIFP) for sulfonamide sensing was fabricated by Pickering emulsion polymerization using UCNP@SiO₂ particles as the stabilizer and sulfamethazine/sulfamerazine as the co-templates. The synthesis conditions of the UCNP@MIFP were optimized, and the synthesized probe was characterized by scanning electron microscopy, Fourier transform infrared spectrometer, thermogravimetric analyzer, and fluorescence spectrometer. The UCNP@MIFPs showed a good adsorption capacity and a fast kinetic feature for the template. The selectivity experiment revealed that the UCNP@MIFP has a broad-spectrum molecular recognition capability. Good linear relationships were obtained over the concentration range of 1-10 ng/mL for sulfamerazine, sulfamethazine, sulfathiazole, and sulfafurazole, with low limits of detection in the range of 1.37-2.35 ng/mL. The prepared UCNP@MIFP has the potential to detect four sulfonamide residues in food and environmental water.

A Comprehensive Review on Upconversion Nanomaterials-Based Fluorescent Sensor for Environment, Biology, Food and Medicine Applications

Near-infrared-excited upconversion nanoparticles (UCNPs) have multicolor emissions, a low auto-fluorescence background, a high chemical stability, and a long fluorescence lifetime. The fluorescent probes based on UCNPs have achieved great success in the analysis of different samples. Here, we presented the research results of UCNPs probes utilized in analytical applications including environment, biology, food and medicine in the last five years; we also introduced the design and construction of upconversion optical sensing platforms. Future trends and challenges of the UCNPs used in the analytical field have also been discussed with particular emphasis.

Nodules of wild legumes as unique natural hotspots of antibiotic resistance genes

Root nodules (RN) of legumes have distinct microenvironment from their symbiotic roots and surrounding soils. The rhizobia can withstand the host-produced phytoalexins and antimicrobial compounds. We thus hypothesize that the wild legume RN may develop unique natural resistome and be antibiotic resistance gene (ARG) hotspots. In this study, in comparison with rhizosphere soil (RS) and bulk soil (BS), we characterized the feature of antibiotic resistance in the RN of two wild legumes, Medicago polymorpha and Astragalus sinicus, by metagenomics. It was shown that the total relative abundance of ARGs followed the order of RN > RS > BS for both legumes. ARGs encoding antibiotic efflux pump predominated in all samples with increased proportion from BS to RN samples for both legumes. Totally 275 ARG subtypes were detected, and diversity of ARGs in RN was significantly lower than in BS samples for both legumes. 32 and 25 unique ARGs subtypes were detected in RN of both legumes. Bacterial community played a key role in shaping nodule-associated resistome because both ARG profiles and bacterial community differed greatly among BS, RS and RN. Rhizobia potentially hosted 10 and 15 ARGs subtypes for both legumes. The number and proportion of plasmid- and ARG-carrying contigs (ACCs) were higher in RN than in BS. Host tracking analysis of plasmid-ACCs suggests that proportion of rhizobial bacteria identified as their hosts decreased from BS to RN samples. No plasmid-ACCs with multiple ARGs were observed in BS samples, whereas they were detected in RN samples of both legumes. Our study showed that even wild legume nodules are unique natural ARG hotspots and enough attention should be paid to the dissemination risk of ARGs posed by globally produced legume crops.

An upconversion nanosensor for rapid and sensitive detection of tetracycline in food based on magnetic-field-assisted separation

Tetracycline, a broad-spectrum antibiotic, has been widely used in disease treatment and other fields. However, due to the unreasonable use, its residue remains in food which eventually harms human health. Here described an upconversion nanosensor for tetracycline detection based on magnetic separation and electrostatic adsorption. To identify tetracycline, tetracycline aptamer, and europium ions (Eu³⁺) were introduced in the system. According to the electrostatic adsorption principle, Eu³⁺ exposed core-shell UCNPs were bound to negative complex of magnetic nanoparticles (MNPs) and aptamer. In the presence of tetracycline, UCNPs separated with MNPs-aptamer and remained in the supernatant by an external magnetic field. Under optimal conditions, the linear detection range of tetracycline was 0.5-1000 ng·mL^-1, and the detection limit was 0.17 ng·mL^-1. It has been successfully applied to detect tetracycline in food samples. The constructed method provided broad prospects for tetracycline detection with the merits of simple operation, high sensitivity, excellent repeatability, and selectivity.

Dipeptide nanoparticle and aptamer-based hybrid fluorescence platform for enrofloxacin determination

A novel fluorescence platform was fabricated for enrofloxacin determination by using cDNA-modified dipeptide fluorescence nanoparticles (FDNP-cDNA) and aptamer-modified magnetic Fe₃O₄ nanoparticles (Fe₃O₄-Apt). The FDNP were prepared via tryptophan-phenylalanine self-assembling. When magnetic Fe₃O₄-Apt incubated with standard solution or sample extracts, the target enrofloxacin was selectively captured by the aptamer on the surface of the Fe₃O₄ nanoparticles. After removing interference by washing with phosphate-buffered saline, the FDNP-cDNA was added, which can bind to the aptamer on the surface of the Fe₃O₄ nanoparticles not occupied by the analyte. The higher the concentration of the target enrofloxacin in the standard or sample solution is, the less the FDNP-cDNA can be bound with the Fe₃O₄ nanoparticles, and the more the FDNP-cDNA can be observed in the supernatant. Fluorescence intensity (E_x/E_m = 310/380 nm) increased linearly in the enrofloxacin concentration range 0.70 to 10.0 ng/mL with a detection limit of 0.26 ng/mL (S/N = 3). Good recoveries (88.17-99.30%) were obtained in spiked lake water, chicken, and eel samples with relative standard deviation of 2.7-6.2% (n = 3).

Development of silica molecularly imprinted polymer on carbon dots as a fluorescence probe for selective and sensitive determination of cetirizine in saliva and urine

A fluorescence probe based on carbon dots (CDs) coated with silica molecularly imprinted polymer (MIPs) was synthesized for selective and sensitive determination of cetirizine (CTZ). Green source carbon dots were firstly derived from orange peels through a microwave method, and had the merits of eco-friendly and low toxicity. Then a thin silica film was formed on the surface of CDs by reverse microemulsion technique, and molecularly imprinted polymer coated on silica-carbon dots. In this scene, CTZ, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were employed as a template, a functional monomer and cross linker, respectively. The obtained CDs-MIPs can selectively bind CTZ through the specific interaction between recognition sites and template, and obey photoinduced electron transfer fluorescence quenching mechanism. Fluorescence dropped linearly in the range of 0.5-500 ng mL^-1, under the optimal conditions, with a detection limit of 0.41 ng mL^-1. Furthermore, the proposed method was successfully intended for the determination of trace CTZ in human saliva and urine samples without the interference of other molecules and ions. And recoveries ranged from 95.8% to 99.8% with relative standard deviation less than 3.0%.

Three-fold interpenetrated metal–organic framework as a multifunctional fluorescent probe for detecting 2,4,6-trinitrophenol, levofloxacin, and l-cystine

A robust Zn(ii) MOF with good chemical and thermal stability, was prepared as an effective fluorescent probe for 2,4,6-trinitrophenol (TNP), levofloxacin (LVX) and l-cystine (l-Cys) with recyclability.

Multi-templates surface molecularly imprinted polymer for simultaneous and rapid determination of sulfonamides and quinolones in water: effect of carbon-carbon double bond

In this work, the effect of a carrier modified with a carbon-carbon double bond (C=C) on preparing multi-templates surface molecularly imprinted polymer MIP (C=C@MIP) for simultaneous detection of sulfonamides and quinolones was investigated. The results showed that the adsorption capacities of the C=C@MIP were obviously higher than those of MIP, which is the carrier without modified C=C, suggesting that C=C played a key role in preparing MIP with higher adsorption capacities. Then, C=C@MIP was used as adsorbents for solid-phase extraction (SPE) and coupled with high-performance liquid chromatography (HPLC) for the simultaneous determination of sulfonamides and quinolones in water. The method showed excellent applicability, with the adsorption capacities of 19.92, 16.38, 12.92, 18.37, 14.49, 12.01, 16.98, 23.33, and 14.29 mg/g for SDZ, STZ, SMZ, SMX, SDM, ENRO, OFL, LOME, and GATI, respectively. The spiked recoveries and relative standard deviations (RSDs) of sulfonamides and quinolones using C=C@MIP were 81.59-100.7 % and 3.75-7.37 %, respectively. The limits of detection (LODs) for SDZ, STZ, SMZ, SMX, SDM, ENRO, OFL, LOME, and GATI were 0.013, 0.012, 0.012, 0.013, 0.014, 0.012, 0.013, 0.015, and 0.015 μg/L, respectively.

Dummy molecularly imprinted membranes based on an eco-friendly synthesis approach for recognition and extraction of enrofloxacin and ciprofloxacin in egg samples

In this work, novel dummy molecularly imprinted membranes (MIMs) were fabricated using the nylon-66 (NY-66) membranes as the subtracts based on an eco-friendly "sandwich" technology with less consumption of organic reagents at mild conditions for recognition and extraction of enrofloxacin (ENR) and ciprofloxacin (CIP) in egg samples. The prepared MIMs were characterized by SEM, ATR-FTIR and TGA, showing the successful construction of uniform and porous polymers on the surface of membranes. A series of adsorption affinity tests were investigated, indicating the prepared materials had specific recognition capacity and excellent stability as novel sorbents. Furthermore, Box-Benhnken design (BBD) and single factor investigations were applied to optimize pretreatment procedures, coupling with Ultra High Performance Liquid Chromatograph (UHPLC) detection. The method showed a good correlation (r²>0.9999) within the linear range of 5.0~5000.0 µg kg^-1, and limit of detection (LOD) of ENR and CIP were 0.3 and 0.7 µg kg^-1, respectively. The mean recovery ranged from 84.5% to 97.0% within relative standard deviations (RSDs) of 10.2%. Finally, ENR and CIP were not detected in 3 batches of egg samples. The current study developed the dummy MIMs as sorbents combined with UHPLC analysis for extraction and detection of target analytes in food matrices.

Lanthanide ion (Ln3+ )-based upconversion sensor for quantification of food contaminants: A review

The food safety issue has gradually become the focus of attention in modern society. The presence of food contaminants poses a threat to human health and there are a number of interesting researches on the detection of food contaminants. Upconversion nanoparticles (UCNPs) are superior to other fluorescence materials, considering the benefits of large anti-Stokes shifts, high chemical stability, non-autofluorescence, good light penetration ability, and low toxicity. These properties render UCNPs promising candidates as luminescent labels in biodetection, which provides opportunities as a sensitive, accurate, and rapid detection method. This paper intended to review the research progress of food contaminants detection by UCNPs-based sensors. We have proposed the key criteria for UCNPs in the detection of food contaminants. Additionally, it highlighted the construction process of the UCNPs-based sensors, which includes the synthesis and modification of UCNPs, selection of the recognition elements, and consideration of the detection principle. Moreover, six kinds of food contaminants detected by UCNPs technology in the past 5 years have been summarized and discussed fairly. Last but not least, it is outlined that UCNPs have great potential to be applied in food safety detection and threw new insight into the challenges ahead.

Biosensing based on upconversion nanoparticles for food quality and safety applications

Food safety and quality regulations inevitably call for sensitive and accurate analytical methods to detect harmful contaminants in food and to ensure safe food for the consumer. Both novel and well-established biorecognition elements, together with different transduction schemes, enable the simple and rapid analysis of various food contaminants. Upconversion nanoparticles (UCNPs) are inorganic nanocrystals that convert near-infrared light into shorter wavelength emission. This unique photophysical feature, along with narrow emission bandwidths and large anti-Stokes shift, render UCNPs excellent optical labels for biosensing because they can be detected without optical background interferences from the sample matrix. In this review, we show how this exciting technique has evolved into biosensing platforms for food quality and safety monitoring and highlight recent applications in the field.

Imprinted Polymers as Synthetic Receptors in Sensors for Food Safety

Foodborne illnesses represent high costs worldwide in terms of medical care and productivity. To ensure safety along the food chain, technologies that help to monitor and improve food preservation have emerged in a multidisciplinary context. These technologies focus on the detection and/or removal of either biological (e.g., bacteria, virus, etc.) or chemical (e.g., drugs and pesticides) safety hazards. Imprinted polymers are synthetic receptors able of recognizing both chemical and biological contaminants. While numerous reviews have focused on the use of these robust materials in extraction and separation applications, little bibliography summarizes the research that has been performed on their coupling to sensing platforms for food safety. The aim of this work is therefore to fill this gap and highlight the multidisciplinary aspects involved in the application of imprinting technology in the whole value chain ranging from IP preparation to integrated sensor systems for the specific recognition and quantification of chemical and microbiological contaminants in food samples.

Sensors/nanosensors based on upconversion materials for the determination of pharmaceuticals and biomolecules: An overview

Upconversion materials have been the focus of a large body of research in analytical and clinical fields in the last two decades owing to their ability to convert light between various spectral regions and their particular photophysical features. They emit efficient and sharp ultraviolet (UV) or visible luminescence after excitation with near-infrared (NIR) light. These features overcome some of the disadvantages reported for conventional fluorescent materials and provide opportunities for high sensitivity chemo-and bio-sensing. Here, we review studies that used upconversion materials as sensors for the determination of pharmaceuticals and biomolecules in the last two decades. The articles included in this review were retrieved from the SCOPUS database using the search phrases: "upconversion nanoparticles for determination of pharmaceutical compounds", and "upconversion nanoparticles for determination of biomolecules". Details of each developed upconversion nanoparticles based sensor along with their relevant analytical parameters are reported and carefully explained.

Interaction of LiYF4:Yb3+/Er3+/Ho3+/Tm3+@LiYF4:Yb3+ upconversion nanoparticles, molecularly imprinted polymers, and templates

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites. Three luminescent molecularly imprinted polymer (MIP) nanocomposites were prepared by in situ polymerization. The relationship between the functional monomers, templates, and upconversion nanoparticles was investigated. Two hydrophilic monomers (acrylic acid (AA) and acrylamide (AAm)) and one hydrophobic monomer (N-tert-butylacrylamide (TBAm)) were employed as functional monomers, while one amino acid (cysteine) and two proteins (albumin and hemoglobin) were employed as the templates to investigate the effect of their interaction with LiYF₄:Yb³⁺/Er³⁺/Ho³⁺/Tm³⁺@LiYF₄:Yb³⁺ core/shell UCNPs on the polymerization process, luminescence properties, and adsorption capacity. The results showed that the UCNPs were embedded in the polymeric matrix to form an irregular quasimicrospherical UCNPs@MIP with diameters ranging from several hundred nanometers to several micrometers depending on the functional monomer. The quenching effect was more pronounced for the adsorption of hemoglobin with UCNPs@MIP compared to cysteine and albumin. In addition, the adsorption capacities of the AA- and AAm-made UCNPs@MIP were greater than those of TBAm-made UCNPs@MIP. The rebinding of the templates onto UCNPs@MIP was very fast and approached equilibrium within 30 min, indicating that the synthesized UCNPs@MIP can be employed as fluorescent probes to offer rapid detection of molecules.

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites.

Novel Carbon-Based Magnetic Luminescent Nanocomposites for Multimodal Imaging

Multifunctional nanocomposites can combine multiple functions into a single nanosystem and thus have attracted extensive interest in various fields. The combination of magnetic and upconversion luminescent nanoparticles into one single nanoplatform, which have a good application in biomedical fields such as bio-magnetic separation, magnetic resonance imaging (MRI), and optical imaging, is highly desirable. Here we reported multifunctional nanocomposites by using hollow carbon sphere to integrate magnetic Fe₃O₄ and upconversion nanoparticles (UCNPs) into one nanosystem. The as-prepared UCNPs/Fe₃O₄@h-C have near-infrared (NIR) luminescence under 980 nm excitation and superparamagnetism. In addition, since the carbon layer can absorb NIR light and transfer it into heat with high efficiency, the nanocomposites can realize photo thermal (PT), upconversion luminescence (UCL) and MRI tri-mode imaging. The UCNPs/Fe₃O₄@h-C might be further utilized as a potential theranostic agent, including its in-depth monitoring through luminescent imaging and MRI diagnosis, as well as its direct use in tumors as a photothermal therapy (PTT) agent.

Preparation of a carboxylated single-walled carbon-nanotube-chitosan functional layer and its application to a molecularly imprinted electrochemical sensor to quantify semicarbazide

Semicarbazide (SEM) is a protein-bound nitrofurazone metabolite that is detrimental to human health. Therefore, to ensure food safety, it is necessary to detect SEM in food samples. To this end, we developed a novel electrochemical sensor to detect SEM by using a molecularly imprinted polymer (MIP) as the recognition element. Computer-aided molecular modelling was performed to guide the synthesis of the MIP, and subsequently, MIP/carboxylated single-walled carbon-nanotubes/chitosan (MIP/SWNTs-COOH/CS) was prepared as the sensing platform to develop the electrochemical sensor. The linear range of the sensor was 0.04-7.6 ng mL^-1, with a detection limit of 0.025 ng mL^-1. The sensor was successfully applied to detect SEM in four different real samples, with recoveries ranging from 83.16% to 93.40%. The results indicated that the fabricated electrochemical sensor can be widely applied to detect SEM in the environment and in agri-food products.

Extraction of activated epimedium glycosides in vivo and in vitro by using bifunctional-monomer chitosan magnetic molecularly imprinted polymers and identification by UPLC-Q-TOF-MS

In this work, efficient, sensitive bifunctional-monomer chitosan magnetic molecularly imprinted polymers (BCMMIPs) were fabricated and successfully applied to concentrate the metabolites of Epimedium flavonoids in rat testis and bone that were later analyzed using UPLC-Q-TOF-MS. Using chitosan and methacrylic acid as co-functional monomers, BCMMIPs exhibited a large adsorption capacity (7.60 mg/g), fast kinetics (60 min), and good selectivity. Chitosan is bio-compatible and non-toxic, and methacrylic acid provides multiple hydrogen bond donors. The BCMMIPs were injected into rat testis to specifically enrich the total flavonoid metabolites in vivo and were used to extract metabolites from bone in vitro. The results showed that the BCMMIPs coupled with UPLC-Q-TOF-MS successfully identified 28 compounds from testis and 18 compounds from bone, including 19 new compounds. This study provided a reliable protocol for the concentration of metabolites from complex biological samples, and several new metabolites of Epimedium flavonoids were found in vivo and in vitro.

Portable Smartphone-Based QDs for the Visual Onsite Monitoring of Fluoroquinolone Antibiotics in Actual Food and Environmental Samples

Accurate onsite profiling of fluoroquinolone antibiotics (FQs) is of vital significance for ensuring food safety and estimating environmental pollution. Here, we propose a smartphone-based QD ratiometric fluorescence-sensing system to precisely report the level of FQs. As a proof of concept, we chose gatifloxacin (GFLX, a typical member of FQs) as the model for the analytical target, which could effectively trigger the fluorescence color variation of QDs from bright yellow-green (∼557 nm) to blue (∼448 nm) through the photoinduced electron-transfer (PET) process, thus yielding an evident ratiometric response. Based on this, the level of GFLX can be reported within a wide linear range from 0.85 nM to 3.6 μM. Moreover, this assay owns a high sensitivity with a low detection limit of 0.26 nM for GFLX and a quick sample-to-answer monitoring time of 5.0 min, manifesting that this platform could be fully qualified for onsite requirements. Interestingly, this portable device has successfully been applied for the onsite detection of GFLX in real food (i.e., milk and drinking water) and environmental (i.e., fish-farming water) samples with acceptable results. This developed platform offers a great promise for the point-of-care detection of FQ residues in practical application with the merits of being label-free, low-cost, and rapid, thus opening a new pathway for the onsite evaluation of food safety and environmental health.

Multi-templates surface molecularly imprinted polymer for rapid separation and analysis of quinolones in water

Rapid separation and analysis of trace quinolones (fleroxacin (FLRX), enoxacin (EN), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENRO), and lomefloxacin hydrochloride (LOME)) in real water samples were achieved by using a multi-templates molecularly imprinted polymer (MIP) based solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography (HPLC). The MIP was prepared via surface molecular imprinting, using the selected quinolones as the templates and mesoporous silica modified magnetic graphene oxide as the carrier. The preparation and adsorption conditions were optimized. The MIP presented high adsorption capacity and wonderful selective recognition for the quinolones, with the adsorption capacities of 20.15, 20.88, 18.01, 20.01, 16.98, and 17.09 mg/g for FLRX, EN, NOR, CIP, ENRO, and LOME, respectively. Meanwhile, a SPE-DLLME-HPLC method for trace detection of FLRX, EN, NOR, CIP, ENRO, and LOME in real water samples was developed and showed outstanding applicability. The spiked recoveries and relative standard deviations (RSDs) were 89.67-100.5%, and 3.59-7.12%, respectively.

[HPLC using capillary monolithic column molecularly imprinted with composite metal organic frame for enrichment and detection of Ponceau 4R in Carthami flos]

OBJECTIVE

To assess the performance of high-performance liquid chromatography (HPLC) combined with capillary monolithic column molecularly imprinted with metal organic frame (UiO-66-NH₂@MIPs capillary monolithic column) for enrichment, purification and detection of Ponceau 4R in Carthami flos.

METHODS

UiO-66-NH₂@MIPs monolithic columns were prepared via in situ polymerization, and the adsorption properties and morphology of the columns were characterized by HPLC, scanning electron microscopy (SEM) and infrared (IR) spectral analysis. HPLC with the prepared columns was performed for detecting the content of Ponceau 4R in Carthami flos samples.

RESULTS

The UiO-66-NH₂@MIPs system showed a good linearity for detecting Ponceau 4R over the concentration range of 0.1-10.0 μg/mL with a correlation coefficient > 0.9999 and a detection limit (S/N=3) of 2.7×10-4 μg/mL. The mean recovery of Ponceau 4R in Carthami flos samples ranged from 82.60% to 105.56%, and the intra-day and inter-day relative standard deviation (RSD) values ranged from 2.4% to 3.4%. The recycling experiment showed that the system could be reused for sensitive detection of Ponceau 4R in Carthami flos. The capacity of UiO-66-NH₂@MIPs column was 0.178 μg/mg, which was superior to that of other monolithic columns (0.089, 0.080, and 0.111 μg/ mg), demonstrating that the addition of UiO-66-NH₂ increased the adsorption capacity of the system. Under the optimized conditions, the UiO-66-NH₂@MIPs-HPLC system had an enrichment factor of over 73 folds with obviously reduced interference by the impurity peaks.

CONCLUSIONS

The UiO-66-NH₂@MIPs column-HPLC system has much better performance for enrichment, purification and detection of Ponceau 4R in Carthami flos than direct HPLC.

Detection of several quinolone antibiotic residues in water based on Ag-TiO2 SERS strategy

Herein, a surface-enhanced Raman scattering (SERS) strategy based on semiconducting substrate was exploited for detection of several antibiotic residues both in ultrapure water system and in actual water system. The as-prepared Ag-TiO₂ (Ag synchronously deposited and doped TiO₂) nanoparticle SERS-active substrate can achieve high sensitive SERS detection for difloxacin hydrochloride, ciprofloxacin, enrofloxacin, danofloxacin and enoxacin (five widely used quinolone antibiotics) in actual water samples, and the detection limits are as low as 4.36 × 10^-12, 7.08 × 10^-11, 3.94 × 10^-11, 3.16 × 10^-11 and 3.15 × 10^-10 mol/L, respectively. These detection limits are far below the maximum of residue limit (3.01 × 10^-7 mol/L) stipulated by the European Union. And, the desirable quantitative relationships can be obtained in a wide concentration range. The recoveries of five antibiotic residues from spiked actual water samples are found to be more than 80.8% with the relative standard deviations between 2.1% and 4.7%. Even, the proposed SERS method can accurately distinguish every antibiotic species from a mixed antibiotic residue sample with multiple antibiotics. And, Ag-TiO₂ nanoparticles can also serve as an efficient photocatalyst for photocatalytic degradation of these antibiotic residues, which provides a multi-functional platform for synchronous determination and degradation of antibiotic residues in real environment.

A highly sensitive and selective "turn-on" fluorescent probe for detection of fleroxacin in human serum and urine based on a lanthanide functionalized metal-organic framework

Cation exchange, a facile and non-destructive post-synthetic modification method, is applied to [(Me)₄N]₂[Pb₆K₆(m-BDC)₉(OH)₂]·H₂O (1) (1,3-H₂BDC = 1,3-benzenedicarboxylic acid) to prepare a series of lanthanide functionalized metal-organic frameworks. The fluorescence properties of Ln³⁺@1 (Ln = Eu, Tb, Sm and Dy) are investigated. The results demonstrate that the framework of 1 is capable of sensitizing both Eu³⁺ and Tb³⁺ ions effectively. Remarkably, the rapid and stable fluorescence sensitization of Eu³⁺@1 can be observed in the presence of fleroxacin in aqueous solution, indicating that the hybrid system can be designed as a highly sensitive and selective probe for fleroxacin. As a novel "turn-on" fluorescent probe, Eu³⁺@1 is regarded as a promising candidate for applications in clinical diagnosis, due to its merits of high antidisturbance, chemical stability and a low detection limit (43.91 ng mL^-1). In this paper, the practical application of luminescent Eu³⁺@1 is highlighted, and its possible sensing mechanism is also described.

A highly sensitive sensor based on a computer-designed magnetic molecularly imprinted membrane for the determination of acetaminophen

In this paper, a sensor based on a magnetic surface molecularly imprinted membrane (MMIP) was prepared for the highly sensitive and selective determination of acetaminophen (AP). Before the experiment, the appropriate functional monomers and solvents required for the polymer were screened, and the molecular electrostatic potentials (MEPs) were calculated by the DFT/B3LYP/6-31 + G method. MMIP with high recognition of AP was synthesized based on Fe₃O₄@SiO₂nanoparticles (NPs) with excellent core-shell structure. Next, a carbon paste electrode (CPE) was filled with a piece of neodymium-iron-boron magnet to make magnetic electrode (MCPE), and MMIP/MCPE sensor was obtained by attaching a printed polymer to the surface of the electrode under the strong magnetic. Due to the stable molecular structure of the electrode surface, the sensor is highly effective and accurate for detection of AP using DPV. The DPV response of the sensor exhibited a linear dependence on the concentration of AP from 6 × 10^-8 to 5 × 10^-5 mol L^-1 and 5 × 10^-5 to 2 × 10^-4 mol L^-1, with a detection limit based on the lower linear range of 1.73 × 10^-8 mol L^-1(S/N = 3). When used for determination of AP in actual samples, the recovery of the sensor to the sample was 95.80-103.76%, and the RSD was 0.78%-3.05%.

Core-Shell Molecularly Imprinted Polymer Nanocomposites for Biomedical and Environmental Applications

Core-shell polymers represent a class of composite particles comprising of minimum two dissimilar constituents, one at the center known as a core which is occupied by the other called shell. Core-shell molecularly imprinting polymers (CSMIPs) are composites prepared via printing a template molecule (analyte) in the coreshell assembly followed by their elimination to provide the everlasting cavities specific to the template molecules. Various other types of CSMIPs with a partial shell, hollow-core and empty-shell are also prepared. Numerous methods have been reported for synthesizing the CSMIPs. CSMIPs composites could develop the ability to identify template molecules, increase the relative adsorption selectivity and offer higher adsorption capacity. Keen features are measured that permits these polymers to be utilized in numerous applications. It has been developed as a modern technique with the probability for an extensive range of uses in selective adsorption, biomedical fields, food processing, environmental applications, in utilizing the plant's extracts for further applications, and sensors. This review covers the approaches of developing the CSMIPs synthetic schemes, and their application with special emphasis on uses in the biomedical field, food care subjects, plant extracts analysis and in environmental studies.

Recent Advances in Magnetic Upconversion Nanocomposites for Bioapplications

The combination of magnetism and upconversion luminescent property into one single nanostructure is fascinating for biological fields, such as multimodal bioimaging, targeted drug delivery, and imaging-guided therapy. In this review, we will provide the state-of-the-art advances on magnetic upconversion nanocomposites towards their bioapplications. Their structure design, synthesis methods, surface engineering and applications in bioimaging, drug delivery, therapy as well as biodetection will be covered.

Recent Advances and Perspectives of Molecularly Imprinted Polymer-Based Fluorescent Sensors in Food and Environment Analysis

Molecular imprinting technology (MIT), also known as molecular template technology, is a new technology involving material chemistry, polymer chemistry, biochemistry, and other multi-disciplinary approaches. This technology is used to realize the unique recognition ability of three-dimensional crosslinked polymers, called the molecularly imprinted polymers (MIPs). MIPs demonstrate a wide range of applicability, good plasticity, stability, and high selectivity, and their internal recognition sites can be selectively combined with template molecules to achieve selective recognition. A molecularly imprinted fluorescence sensor (MIFs) incorporates fluorescent materials (fluorescein or fluorescent nanoparticles) into a molecularly imprinted polymer synthesis system and transforms the binding sites between target molecules and molecularly imprinted materials into readable fluorescence signals. This sensor demonstrates the advantages of high sensitivity and selectivity of fluorescence detection. Molecularly imprinted materials demonstrate considerable research significance and broad application prospects. They are a research hotspot in the field of food and environment safety sensing analysis. In this study, the progress in the construction and application of MIFs was reviewed with emphasis on the preparation principle, detection methods, and molecular recognition mechanism. The applications of MIFs in food and environment safety detection in recent years were summarized, and the research trends and development prospects of MIFs were discussed.

Molecularly Imprinted Polymer-Based Hybrid Materials for the Development of Optical Sensors

We report on the development of new optical sensors using molecularly imprinted polymers (MIPs) combined with different materials and explore the novel strategies followed in order to overcome some of the limitations found during the last decade in terms of performance. This review pretends to offer a general overview, mainly focused on the last 3 years, on how the new fabrication procedures enable the synthesis of hybrid materials enhancing not only the recognition ability of the polymer but the optical signal. Introduction describes MIPs as biomimetic recognition elements, their properties and applications, emphasizing on each step of the fabrication/recognition procedure. The state of the art is presented and the change in the publication trend between electrochemical and optical sensor devices is thoroughly discussed according to the new fabrication and micro/nano-structuring techniques paving the way for a new generation of MIP-based optical sensors. We want to offer the reader a different perspective based on the materials science in contrast to other overviews. Different substrates for anchoring MIPs are considered and distributed in different sections according to the dimensionality and the nature of the composite, highlighting the synergetic effect obtained as a result of merging both materials to achieve the final goal.

Ultrasensitive ciprofloxacin assay based on the use of a fluorescently labeled aptamer and a nanocomposite prepared from carbon nanotubes and MoSe2

A nanocomposite was prepared from carbon nanotubes and MoSe₂ (CNT-MoSe₂). This nanomaterial quenches the fluorescence of fluorescein-labeled aptamers. When ciprofloxacin (CIP) binds to the aptamer, an aptamer/G-quadruplex complex will be formed and the interaction between labeled aptamer and CNT-MoSe₂ nanostructures is weakened. This leads to significant fluorescence recovery. Under optimized experimental conditions, the limit of detection is 0.63 ng mL^-1 with a good linearity in the range from 0.63 to 80 ng mL^-1. The assay was applied to the determination of CIP in spiked milk, and the recoveries range between 94.3 and 97.0% (n = 3). Conceivably, the method is a generic approach that can be extended to the determination of other analyte for which adequate aptamers are available. Graphical abstract Schematic presentation of CNT-MoSe₂ quenching based aptamer assay for the detection of ciprofloxacin. The assay exhibits good selectivity, stability and reproducibility, and low limit of detection.

Fluorometric determination of ciprofloxacin using molecularly imprinted polymer and polystyrene microparticles doped with europium(III)(DBM)3phen

The authors describe a microparticle-based system for the detection of the fluoroquinolone antibiotic ciprofloxacin. The method is using the tris(dibenzoylmethane)(1,10-phenanthroline)europium(III) luminophore in polystyrene microparticles along with a molecularly imprinted polymer (MIP) for ciprofloxacin. If ciprofloxacin is captured by the MIP, it quenches the fluorescence of the luminophores. Fluorescence drops linearly in the 0.5-100 μg L^-1 ciprofloxacin concentration range, and the detection limit is 92 ng L^-1. The method was applied to the analysis of fish samples to assess the analytical performance of the probe. Recoveries ranged from 85.4 to 86.6%, and relative standard deviations between 2.1 and 3.9% (for n = 5). Graphical abstract Schematic presentation of a microparticle-based probe using the tris(dibenzoylmethane)(1,10-phenanthroline)europium(III) luminophore in polystyrene particles along with a molecularly imprinted polymer for ciprofloxacin. After removal of template, carboxylic groups left in the probe can bind to ciprofloxacin through hydrogen bonds.

Multifunctional NaYF4:Yb,Er@PE3@Fe3O4 nanocomposites for magnetic-field-assisted upconversion imaging guided photothermal therapy of cancer cells

Magnetic-field-assisted sensitive upconversion luminescence imaging and enhanced photothermal therapeutic efficacy were achieved with multifunctional NaYF₄:Yb,Er@PE3@Fe₃O₄ nanocomposites.

Highly efficient detection of ciprofloxacin in water using a nitrogen-doped carbon electrode fabricated through plasma modification

We developed a novel electrochemical sensor based on nitrogen plasma modification to effectively detect ciprofloxacin in water.

A convenient fluorescent assay for quinolones based on their inhibition towards the oxidase-like activity of Cu2+

This work reports on a novel and convenient fluorescent assay for four quinolones including nalidixic acid, cinoxacin, ciprofloxacin and moxifloxacin, with Cu²⁺-triggered and quinolone-inhibited oxidation of o-phenylenediamine.