Magnetic Molecular Imprinting Research Articles

High enrichment and sensitive measurement of oxytetracycline in tea drinks by thermosensitive magnetic molecular imprinting based magnetic solid phase extraction coupled with boron doped carbon dots

As a typical kind of new pollutants, there are still some challenges in the rapid detection of antibiotics. In this work, a sensitive fluorescent probe based on boron-doped carbon dots (B-CDs) in combination with thermo-responsive magnetic molecularly imprinted polymers (T-MMIPs) was constructed for the detection of oxytetracycline (OTC) in tea drinks. T-MMIPs were designed, fabricated and employed to enrich OTC at trace level from tea drinks, and B-CDs were utilized as the fluorescent probe to detect the concentration of OTC. The proposed method exhibited good linear relationship with OTC concentration from 0.2 to 60 μg L−1 and the limit of detection was 0.1 μg L−1. The established method has been successfully validated with tea beverages. Present work was the first attempt application of T-MMIPs in combination with CDs in detection of OTC, and demonstrated that the proposed method endowed the detection of OTC with high selectivity, sensitivity, reliability and wide application prospect, meanwhile offered a new strategy for the method establishment of rapid and sensitive detection of trace antibiotics in food and other matrices.

Development of magnetic molecularly imprinted polymers for selective extraction of Benzoxazolinone-type alkaloids from acanthus plants

Benzoxazolinone-type alkaloids found in Acanthus ebracteatus and Acanthus ilicifolius Linnaeus possess various beneficial properties, such as antileishmanial, antipyretic, analgesic, antibacterial, and antioxidant effects. In this study, we employed a surface imprinting technique on nanomaterials. We utilized functionalized Fe3O4@SiO2NH2 as a scaffold, with 2-benzoxazolinone and 2H-1,4-benzoxazin-3(4H)-one serving as dual templates, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and 2,2-azodiisobutyric nitrile (AIBN) as the initiator. Prior to polymerization, we screened functional monomers using ultraviolet (UV) spectroscopy. The resulting magnetic surface molecular imprinting polymer (Fe3O4@SiO2@MIP) was thoroughly characterized using Fourier transform infrared spectrometry (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). We also conducted assessments of its adsorption isotherms, dynamics, and selective binding capabilities. Our findings indicate that the MIPs exhibited exceptional selective recognition performance. Through meticulous screening and optimization of extraction and separation conditions, we established an LC‒MS/MS method based on magnetic solid-phase extraction technology. The method exhibited a recovery range of 78.80–106.99 % (RSD, 0.46–3.31 %) for 2-benzoxazolinone, with a limit of detection (LOD) and limit of quantification (LOQ) of 2.85 and 9.00 μg L−1, respectively. For 2H-1,4-benzoxazin-3(4H)-one, the method yielded a recovery range of 84.75–103.53 % (RSD, 0.07–5.96 %), with an LOD and LOQ of 3.60 and 12.60 μg L−1, respectively, in real samples. The resulting Fe3O4@SiO2@MIP demonstrated a high capacity for class-specific adsorption.

Optimal preparation of pyrene magnetic molecularly imprinted polymers by simulation calculation and study of its adsorption properties

The combination of magnetic molecular imprinting technology and simulation calculation has gained significant attention in the field of sample pretreatment due to its ability to reduce solvent consumption during the preparation process. However, traditional simulation methods have limitations in visualizing the π-π stack mechanism between target molecules and functional monomers. This study introduces a new method called interactive regional indicators, which can effectively select suitable functional monomers for the preparation of pyrene magnetic molecular imprinting polymers (PMs) by visualizing weak interactions. The results showed that PMs had higher adsorption capacity faster adsorption rate, and good selectivity, stability, and reproducibility. PMs were applied to the adsorption of tap water and vegetable oil adsorption and its structural analogs. The results show that the LODs (S/N = 3) of PMs in water and canola oil samples are 0.82 × 10−5-4.1 × 10−5 mg/L and 0.576 × 10−3-4.347 × 10−3 mg/L, respectively, with high accuracy and precision. This method can be used for the pretreatment of pyrene in many substrates. It verifies the accuracy of theoretical calculation and provides some data support for theoretical calculation combined with experimental research.

Highly selective and sensitive determination of doxycycline integrating enrichment with thermosensitive magnetic molecular imprinting nanomaterial and carbon dots based fluorescence probe

Doxycycline (DOX), a typical tetracycline antibiotic, is widely used because of its excellent antibacterial activity. To develop effective method for DOX has attracted much more attention. Herein, a new detection technology integrating magnetic solid phase extraction (MSPE) based on thermosensitive magnetic molecularly imprinted polymers (T-MMIPs) and fluorescence spectrometry based on carbon dots (CDs) was established. Thermosensitive magnetic molecularly imprinted polymers (T-MMIPs) was designed for selective enrichment of trace DOX. The synthesized T-MMIPs showed excellent selectivity for DOX. The adsorption performance of T-MMIPs varied with temperature in different solvents, which could achieve the enrichment and rapid desorption of DOX. In addition, the synthesized CDs had stable fluorescent property and better water-solubility, and the fluorescence of CDs was significantly quenched by DOX due to the internal filtration effect (IFE). Under the optimized conditions, the method resulted in good linearity over the range from 0.5 to 30 μg L−1, and the limit of detection was 0.2 μg L−1. The constructed detection technology was validated with real water samples, and excellent spiked recoveries from 92.5 % to 105.2 % were achieved. These data clearly indicated that the proposed technology was rapid, highly selective, environmentally friendly, and possessed significant potential application and development prospects.

Synthesis of MRGO@ZIF-7-Based Molecular Imprinted Polymer by Surface Polymerization for the Fast and Selective Removal of Phenolic Endocrine-Disrupting Chemicals from Aqueous Environments

In this study, Zn(NO3)2·6H2O was selected as the metal source, and ZIF-7-modified magnetic graphene-based matrix materials (MRGO@ZIF-7) were prepared by in situ growth. ZIF-7 modified magnetic graphene-based molecular imprinting complexes (MRGO@ZIF7-MIP) were successfully synthesized by a surface molecular imprinting technique using bisphenol A (BPA) as the template molecule. The obtained experimental materials were characterized by X-ray diffraction (XRD), Brunner–Emmet–Teller (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS). The proper adsorption and selective recognition ability of the MRGO@ZIF7-MIP were studied by an equilibrium adsorption method. The obtained MRGO@ZIF7-MIP showed significant molecular recognition of bisphenol A (BPA) and good selectivity and reproducibility for BPA in different aqueous environments such as drinking water, river water, and lake water. These properties make this material potentially applicable for the efficient removal of phenolic endocrine disruptors in real water environments.

Multivariate optimization of magnetic molecular imprinting solid-phase extraction to entrap rhodamine B in seawater

A highly efficient sample clean-up and preconcentration using novel magnetic molecularly imprinted polymers (MMIPs) as dispersant sorbents was developed for selective entrapment and rapid detection of rhodamine B from seawater samples coupled with fluorescence spectrometry. The MMIPs were synthesized by surface imprinting technique employing nano-Fe3O4 particles as carriers and rhodamine B as template molecule. The characterizations of prepared nanocomposites were fully investigated and molecular recognition assays exhibited high affinity and selectivity for rhodamine B. As magnetic adsorbents, several essential factors that affecting extraction efficiency during sample preparation were systematically optimized via response surface methodology with Box–Behnken design. Under optimum conditions, the proposed method presented a wide linear response over the concentration range of 2.5 ∼ 112.5 μg L−1, with a limit of detection (LOD) of 0.45 μg L−1. Finally, five seawater samples collected from Jiaozhou Bay were analysed and the recoveries of the spiked samples were found from 94.90 to 102.48% with relative standard deviations lower than 5.36% (n = 3). The results show that the developed method could be considered as an attractive and sensitive alternative for rapid analysis of organic dyes at trace levels in complex seawater matrix.

Histidine detection and signal amplification based on magnetic molecularly imprinted particle and Cu2+ coordination

Magnetic molecularly imprinted (MMIP) particle-based electrochemical sensors are promising for wide detection applications. However, current sensing strategies mainly rely on electrochemical active analytes because of the lack of signal conversion and amplification methods. Herein, a novel histidine (His) sensor was designed based on MMIP particle and metal coordination of Cu2+ with His and cysteine (Cys). The whole determination processes were separated into recognition, coordination and detection steps. The target His in complicated samples can be selectively captured by the MMIP particles to ensure the specificity, then coordinated with Cu2+ and detected at magnetic electrodes under a specific condition to avoid contamination. Highly chemically stable MMIP particles can be prepared by the sol-gel method in large quantities at a very low cost. Additionally, the signal of Cu2+ can be significantly amplified using Cys modified Au nanoparticles. The optimized detection conditions were investigated by voltammetry. The sensor allowed His determination in a wide concentration range over 5-orders of magnitude with a low detection limit of 0.01 μM, which also expressed a promising performance in spiked water and serum samples. Accordingly, the proposed sensing strategy is beneficial for the design and preparation of novel MMIP particle-based electrochemical sensors.

Multi-functional magnetic molecular imprinting probe for visual detection of IgY antibodies.

Egg yolk antibodies (IgY)are analternative to mammalian antibodies, which have been successfully applied in treatment ofdisease, asimmunochemical reagents and asfood additives. A fast, accurate, and easy-to-operate detection method for IgY antibodies is needed. Herein, we developed a rapid and cost-effective colorimetric assay for the ultrasensitive detection of anti-S. aureus IgY antibodies using multi-functional magnetic molecularly imprinted polymers (MMIPs). The prepared MMIPs can recognize, adsorb, and separate the analyte from the matrix efficiently, and oxidize TMB to generate a colorimetric signal within ~ 60min. As low as 0.013mg·mL-1 was able to be detected by using this method. The visual detection limit reached 0.02mg·mL-1. By testing the IgY in milk samples, the feasibility was verified.

One-Pot Strategy as a Green and Rapid Method to Fabricate Magnetic Molecularly Imprinted Nanoparticles for Selective Capture of Sulfonylurea Herbicides.

Magnetic solid-phase extraction (MSPE) based on molecularly imprinted nanoparticles (MINs) has attracted wide attention in sample pretreatment because it combines the merits of high selectivity and quick extraction procedures. However, laborious, time and solvent-consuming steps were involved in the synthesis of magnetic imprinted particles in existing approaches. To circumvent this dilemma, a green and rapid "one-pot" strategy was proposed to prepare MINs. Halosulfuron-methyl (HSM) was selected as a template molecule, and Gaussian 09 simulation software was employed to screen the 2,4,6-trivinylboroxin pyridine complex (TBP) as a functional monomer. Subsequently, the fabrication was simply conducted using a hydrothermal approach by mixing self-assembly solution of TBP-HSM, Fe3+, Fe2+, dimethyl sulfoxide, and azobisisobutyronitrile in one-pot with a total reaction time of 3.0 h. Various characterized results well evidenced the successful imprint of HSM and the resultant HSM-MINs presented satisfying superparamagnetism and saturation magnetism. Under the optimized parameters, the obtained HSM-MINs displayed good recognition capability and selectivity toward HSM (recognition coefficient was 2.60), as well as a satisfactory saturation adsorption capacity (1781 μg/g). The quantification of sulfonylurea herbicides at trace levels in environmental water and soil samples was selected as a paradigm to demonstrate the practicality and reliability of HSM-MINs/MSPE. The present study provides a convenient, reliable, and green approach for fabricating a magnetic molecular-imprinting adsorbent for MSPE.

Facile one-pot synthesis of magnetic molecular imprinting polymers as a novel adsorbent for the enrichment of imidacloprid based on a magnetic dispersive micro-solid-phase extraction in water samples

The pesticide residues have become one of the issues in the fields of environmental health and food safety. Herein, an effective method was successfully developed to rapidly determine imidacloprid in environmental water samples based on magnetic molecular imprinted polymers (MMIP) coupled with high-performance liquid chromatography. MMIP were creatively synthesized in one-pot synthesis step via the nucleation process of Fe3O4 magnetic nanoparticles and the polymerization process of molecular imprinted polymers simultaneously, using imidacloprid as template and dopamine as functional monomer. The parameters effected on the extraction efficiency, including pH value and the amount of the adsorbent, have been optimized. Under the optimal conditions, MMIP was used to extract imidacloprid in water samples with excellent recovery (88–97.3%) and precision (1.2–3.3%). Therefore, magnetic nanoparticles-based dispersion solid-phase extraction could be a good candidate for highly efficient extraction of imidacloprid without complicated operations.

Rapid and selective extraction of norfloxacin from milk using magnetic molecular imprinting polymers nanoparticles

The magnetic molecular imprinting polymers nanoparticles (MMIPs NPs) for the extraction of norfloxacin (NOR) were prepared by self-polymerization of dopamine onto the surface of (3-Aminopropyl)triethoxysilane (APTES)-modified Fe3O4 NPs. The MMIPs NPs were characterized by FT-IR spectroscopy, XRD, VSM and TEM. The characterization results show that the MMIPs NPs possess superparamagnetic characteristic with the saturated magnetization value of 38.6 emu/g, and the average particle size of about 14.3 nm. Furthermore, the adsorption performance of the MMIPs NPs was evaluated by the static, dynamic, selective adsorption and reusability experiments. The adsorption capacity of MMINs NPs for NOR is 14.2 mg/g with an imprinted factor of 2.1. About 82.4–102.4% of the added NOR (20, 40, 60 μg/mL) were recovered from fortified milk samples with MMIPs NPs as sorbent. Moreover, the MMIPs NPs can be reused for at least six times.

Trace carbonyl analysis in water samples by integrating magnetic molecular imprinting and capillary electrophoresis.

In order to obtain high derivatization efficiency, the overuse of derivative agent 2,4-dinitrophenylhydrazine (2,4-DNPH) is necessary for carbonyl detection. But, the 2,4-DNPH residue will cause background interferences and limit the pre-concentration factor of the target analytes. In order to overcome the bottleneck problems, the magnetic molecularly imprinted polymer based solid-phase extraction (MMIPs-SPE) method was developed with 2,4-dinitroaniline (2,4-DNAN) as the dummy template. The characteristics and selectivity of the MMIPs were investigated. Under the optimized conditions, the enrichment of carbonyls-DNPH derivatives with simultaneous removal of the surplus 2,4-DNPH was achieved. By coupling with capillary electrophoresis (CE), a satisfactory analytical performance was obtained with the detection limit ranging from 1.2 to 8.7 μg L−1 for 8 carbonyls. The MMIPs-SPE-CE method was applied successfully for the carbonyl assessment in stream water, tap water and bottled water. In addition, the migration of carbonyls in bottled drinking water was investigated under UV irradiation and heating.

Determination of aldehydes in water samples by coupling magnetism-reinforced molecular imprinting monolith microextraction and non-aqueous capillary electrophoresis

Excess 2, 4-dinitrophenylhydrazine (2, 4-DNPH) is often applied for the derivatization of aldehyde prior to the chromatographic analysis. However, the residual 2, 4-DNPH may cause background interference and limit the enrichment efficiency of trace aldehydes. To overcome the above bottle-neck problems, improve the extraction efficiency and omit the manipulation for changing the polarity of solvent for the hydrophobic analytes separation, a new method combining magnetism-reinforced in-tube solid phase microextraction (IT-SPME) technique with non-aqueous capillary electrophoresis (NACE) was developed. The monolithic extraction cartridge was prepared in situ inside a capillary and doped with magnetic molecular imprinting polymers (mMIPs). The selective and efficient extraction of the derived analytes with simultaneous removal of the superfluous derivatization agent was achieved owing to the combined effect of molecular imprinting and magnetism reinforcement. By coupling with NACE, the highly hydrophobic effluent can be analyzed directly. The LODs of the method are between 0.0032~0.0049 mg L−1 and the recoveries are between 87.3~99.8% for the tested aldehydes. The developed approach is sensitive enough for detection of surface (drinking) water. The aldehydes in real water samples have been detected by this method, showing results that are in good agreement with the standard SPE-HPLC method.

Synthesis, characterization, and evaluation of a magnetic molecular imprinted polymer for 5-fluorouracil as an intelligent drug delivery system for breast cancer treatment

Magnetic carriers-based molecular imprinting has become one of the most interesting phenomena in the drug delivery field. In this study, we endeavor to devise an effective magnetic drug carrier via imprinting technology for 5-fluorouracil and investigate its anticancer activity toward breast cancer treatment. In this case, methacrylic acid and trimethylolpropane triacrylate were chosen for imprinting 5-fluorouracil on the magnetic fluorescent core. With this aim, fluorescein isothiocyanate was utilized as a fluorescent agent. FT-IR, EDX, XRD, VSM, FESEM, TEM, and BET analysis were used to characterize the synthesized carrier. According to adsorption studies, the adsorption of 5-fluorouracil was followed by Freundlich isotherm (QMAX: 121.6 mg/g) in a fast second-order kinetic model (6 min) in our proposed carrier. Afterward, based on the release studies the Higuchi dynamic model was suggested for leaching of 5-fluorouracil from the carrier. Eventually, the cytotoxicity effect of the projected carrier on MCF-10 and MCF-7 cell lines was investigated. In this case, the magnetic carrier has shown 61% cytotoxicity on cancer cells which were about 25 times greater than the pure drug, but it had no significant effect on normal cells. In all steps, the non-imprinted carrier was investigated as a comparison. This study has shown that our proposed magnetic nanocarrier can effectively be utilized in breast cancer treatment. The synthesis of magnetic molecular imprinted for 5-FU toward the breast cancer treatment eliminates the MDR of cancer cell toward the 5-FU.

Specific adsorption of tetracycline from milk by using biocompatible magnetic molecular imprinting material and evaluation by ECD

Biocompatible magnetic molecularly imprinted polymers (BMMIPs) were prepared with Zein for the first time, and were used to enrich tetracycline compounds selectively. Innovative combination of BMMIPs and electrochemistry to obtain lower detection line to satisfy industrial detection demands. Using Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe3O4 particles. The scanning electron microscope, transmission electron microscope and X-ray diffraction technologies were used to characterize BMMIPs. Through optimization, BMMIPs attained large adsorption capacity (236.40 mg/g) with fast kinetics (40 min) and followed the Langmuir isotherm and pseudo-second-order kinetic models. BMMIPs had good recognition ability, the selective factors of oxytetracycline, chlortetracycline, doxycycline were 4.78, 4.23, and 3.39, respectively. Excellent linearity was attained in the range of 0.025–500 μg/mL, with low detection limits and low quantitation limits of 0.025 and 0.083 μg/mL. According to our exploring, BMMIPs was ideal materials for enrichment of tetracycline in complex biological samples.

Magnetic molecularly imprinted multishell particles for zearalenone recognition

This paper deal with the synthesis and characterization of a new class of magnetic molecularly imprinted (MIP) particles, with selective recognition properties for Zearalenone (ZEN), an estrogenic mycotoxin. These particles present a multishell structure, comprising a magnetic core, constituted by spherical aggregates of magnetite nanoparticles (Fe3O4 nanoparticles), covered by a thin silica layer and surrounded by a molecularly imprinted (MIP) polymer shell, obtained employing quercetin as the dummy template and 4-vinylpyridine as the functional monomer. A multistep synthetic procedure was developed leading to spherical particles with a mean diameter of approximately 900 nm and a high magnetic fraction. The MIP were tested for ZEN re-binding properties. ZEN-MIP material had 55-fold more affinity for ZEN than the corresponding non-imprinted (NIP) material, that highlighting their potential for ZEN concentration from complex food matrices.

Effect of biomolecule chemical structure on the synthesis of surface magnetic molecularly imprinted polymer in aqueous solution using various monomers for high-capacity selective recognition of human insulin

Magnetic molecular imprinting technique was used for the detection of human insulin. The structure and binding sites of insulin determined by the use of Cn3D software were considered in the selection of functional monomers types and ratios. Methacrylic acid (MAA) was chosen as the electrostatic functional monomer and acrylamide (AAm) as the neutral monomer with a cross-linker of methylenebisacrylamide (MBAAm) for surface imprinting onto vinyl-functionalized Fe3O4 nanoparticles (MNPs). The effect of factors including the monomers' molar ratio, pH of the synthesis media, template concentration, type of eluent solution, and elution time was investigated on the characteristics and performance of molecularly imprinted polymers along with the molecular analysis of the system at the elution stage. The results revealed the importance of considering the template structure. The best result was obtained with an imprinting factor equal to 2.2 by magnetic molecularly imprinted polymers at the molar ratio of 20:100:5 for MAA:AAm:MBAAm (on the basis of 1 M of insulin), synthesized in phosphate buffer (pH = 6) and eluted with methanol/acetic acid (9/1, v/v) solution for 72 h. Its high selective recognition to insulin in the presence of a competitor demonstrated the separation ability of the imprinted polymer to the template molecule.

Magnetic molecularly imprinted polymer nanoparticles for separating aromatic amines from azo dyes – Synthesis, characterization and application

In order to improve the tedious pretreatment process of the detection of aromatic amines, a new material based on magnetic molecular imprinting technology which could specifically recognize 4,4′-Methylene bis(2-chloroaniline) and perform rapid enrichment was prepared. MIPs were synthesized on the surfaces of the magnetic silica gel spheres via thermal initiations using 2-Vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and 2,2′-azo-bis-isobutyronitrile as the initiator. Fourier transform infrared spectroscopy, transmission electron microscope, nitrogen sorption measurement and magnetic characterization were used to characterize the MIPs. The adsorption kinetic curve, adsorption isotherm and selective adsorption were measured by a static method. The results showed that the adsorption reached equilibrium in about 30 min and the maximum adsorption capacity was 6.31 μmol/g. In addition, the adsorption process fitted well to a pseudo-second order model and the equilibrium data fitted to a Freundlich equation. The method with molecularly imprinted polymer was evaluated by the blank sample spiked with MOCA by UV–vis absorption spectra. The average recovery was in the range of 82.36–87.53% with RSD value lower than 9.07%. These results prove that this new method is effective in the rapid detection of the carcinogenic aromatic amine released from azo dyes.

Magnetic molecular imprinting polymers based on three-dimensional (3D) graphene-carbon nanotube hybrid composites for analysis of melamine in milk powder

A novel analytical method for melamine in milk powder has been developed and exploited with three-dimensional (3D) magnetic molecularly imprinted polymers (MMIPs) combining with liquid chromatography-tandem mass spectrometry. The 3D MMIPs were synthesized with graphene-carbon nanotube hybrid composite as carrier which can increase the accessible surface area. The products were characterized, and the binding affinity was investigated by isothermal absorption, kinetic adsorption and selective adsorption. The results showed that the 3D MMIPs exhibited high adsorption capacity with maximum adsorption capacity of 123.1 mg g−1, fast adsorption rate (10 min) and high selectivity toward melamine. Various affecting extraction parameters were evaluated. The limit of detection was 0.00045 mg kg−1 and the recoveries were ranged from 90.3% to 95.7%. The precisions (RSDs) were lower than 4.7%. This method was applied for analyzing six milk powder samples. The result was in agreement with that obtained by the state standard method used in China.

Separation of bovine hemoglobin using novel magnetic molecular imprinted nanoparticles.

Magnetic molecular imprinted nanoparticles (MMIPs), combining the progressiveness of magnetic nanoparticles and surface molecular imprinting technology, have attracted increasing attention because of the high efficiency and specificity in isolation and enrichment of the target protein. This study focused on the preparation of bovine hemoglobin MMIPs with bovine hemoglobin (BHb) as the template protein and the molecular imprinted polymer covering the functional magnetic nanoparticles modified with silane and acrylic groups. The physicochemical characteristics as well as the dynamics and isothermal adsorption properties of the generated nanoparticles were investigated to determine their efficiency and specificity in the adsorption of target protein. The maximum adsorption of the target protein was 169.29 mg g−1 at a specific pH, which was much larger than those obtained in some other research reports. MMIPs showed favorable selectivity towards BHb in a mixture of three different proteins. The results indicated the significant effects and broad prospects of MMIPs in the isolation and enrichment of specific proteins in the field of food, medicine and biological research.