Preparation and Characterization of Molecularly Imprinted Polymer as SPE Sorbent for Melamine Isolation

Novel Discrete and Imprinted Fluoride-Selective Sensors: Bridging the Gap from DMSO to Aqueous Samples

Fluoride in drinking water has beneficial or harmful health effects depending on its concentration. This highlights the need for new low-cost and portable sensors capable of in situ monitoring of F- ions. Unfortunately, achieving high levels of water compatibility and fluoride specificity remains a challenge. Here, four new urea-based discrete sensors are prepared and characterized. The sensors containing anthracenyl- (5) and 9H-fluorenyl- (7) signaling units exhibit intense luminescent emissions in dimethyl sulfoxide, the former being particularly sensitive and selective to fluoride. In water, 5 displays a superior sensitivity (871 M-1) and a detection limit (8 µm) below international guidelines, albeit with cross-sensitivity to H2PO4‾. To enhance the performance, 5 and 7 are embedded into a fluoride-imprinted polymeric matrix to give solid-state sensors (5P and 7P, respectively). 5P shows good sensitivity (360 M-1) and specificity in water. Besides, it has a low detection limit (35 µm) and a response linear range (118-6300 µm) encompassing the limit established by the Environmental Protection Agency (211 µm). Furthermore, 5P also displays good reusability and adequate recovery values in real-sample testing (102 ± 2%), constituting the first example of a low-cost anion-imprinted polymeric probe tailored for the selective sensing of fluoride in aqueous samples.

Synthesis of molecularly imprinted polymer with a methacrylate derivative monomer for the isolation of ethyl p-methoxycinnamate as an active compound from Kaempferia galanga L. extracts

Kaempferia galanga rhizome is traditionally used as a treatment for various diseases. Ethyl p-methoxycinnamate (EPMC), which constitutes up to 31.77% of the total essential oil, is the main/marker compound. EPMC is responsible for various pharmacological activities of Kaempferia galanga rhizome. According to the existing research, the isolation yield of EPMC is still meager, namely 0.50-2.50%; thus, a new EPMC isolation method is needed to produce better results. In this study, after determining the association constant and obtaining the Jobs plot between methacrylate derivative monomers and EPMC, a molecularly imprinted polymer for solid phase extraction (MI-SPE) was synthesized through bulk polymerization with EPMC as a template, methacrylic acid as a monomer, TRIM/EDGMA as a crosslinker in a ratio of 1 : 4 : 20 (MIP1) or 1 : 7 : 20 (MIP2). BPO was used as an initiator and n-hexane was used as a porogen. The synthesis of the NIP was also conducted using the same ratio but without the template. The MIPs were then characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) measurements, and their analytical performance was evaluated through adsorption capacity and selectivity. The results indicate that MIP2 exhibits better analytical performance with an adsorption capacity value of 0.0813 mg g-1. The selectivity of MIP2 was tested using EPMC analog compounds, namely ethyl cinnamic (EC), cinnamaldehyde (CD), and kaempferol (KF), with imprinting factor (IF) values of 17.436, 1.539, and 0.06, respectively. Lastly, MIP2 was applied to the SPE cartridge for the isolation of EPMC from Kaempferia galanga rhizome extract, and showed a percentage recovery of 82.40% for the ethanol extract, 68.05% for the ethyl acetate extract, and 65.27% for the n-hexane extract. MI-SPE 2 gives high purity results for the ethanol, ethyl acetate, and n-hexane extracts, with purities of 97.00%, 97.63%, and 99.59%, respectively. These results indicate that the MI-SPE technique shows great potential as a new method for isolating EPMCs with high yield and purity.

Template-assisted synthesis of molecularly imprinted polymers for the removal of methyl red from aqueous media

This study entails the synthesis of molecularly imprinted polymers (MIPs) with good selectivity coefficients for azo dye as a potential sorbent material to extract azo dye from polluted aqueous media. A series of MIPs for methyl red (MR) as a template, were synthesized by changing the molar ratio of functional monomers, via precipitation polymerization format of non-covalent approach. Water-soluble functional monomer; acrylic acid (AA) was used to weave the frame work of polymers while ethylene glycol dimethacrylate (EGDMA) was utilized as crosslinking monomer. The impact of different experimental parameters, such as mole ratio of monomer (functional) to crosslinking monomer on the molecular recognition was investigated. The highly efficient and selective MR-MIP was used for the removal of spiked MR dye from different water samples. The selected imprinted polymer, MR1-MIP was able to selectively remove the MR molecules from aqueous media. A significant amount of dye was removed by MR1-MIP from the river water samples with a high degree of removal efficiency i.e. 92.25%. The imprinting factor of 3.75 for MR1-MIP indicated that the high selectivity in terms of adsorption for MR. A minimum loss of only ~ 3.35% in the removal efficiency within ten sequential cycles of adsorption-desorption study evidenced that MR-MIPs could be used as the most cost effective and best sorbent for the removal of MR from polluted water. Furthermore, the structural properties of MR-MIPs were characterized by FTIR and EDX, whereas TGA, SEM and BET were used to describe the thermal, morphological and surface structures of the particles, respectively.

Synthesis of Mesoporous Silica Imprinted Salbutamol with Two TEOS/MTES Ratio Compositions through the Direct Incorporation Method for Salbutamol Separation

Molecularly imprinted mesoporous silica (MIPMS) is one of the methods to improve site accessibility molecule target on molecularly imprinted polymer (MIP) for application in solid-phase extraction (SPE). The MIPMS was prepared using salbutamol sulfate as template molecule, cetyltrimethylammonium bromide as a directing agent, and tetraethyl orthosilicate and methyltriethoxysilane were used as silica precursor and organosilane. In this study, two TEOS : MTES ratios were used. The MIPMS-2 with 3 : 1 ratio of TEOS : MTES has better analytical performance than the MIPMS-1 with 2 : 1 ratio of TEOS : MTES. The adsorption capacity of MIPMS-2 was about 0.0934 mg/g, and it was 0.0407 mg/g for NIPMS-2. The extraction ability of MIPMS-2 was good, with a recovery of about 104.79% ± 1.01% of salbutamol in spiked serum. The imprinting factor (IF) value obtained is 1.2. When serum was spiked with salbutamol and terbutaline, the ability of NIPMS-2 to recognize salbutamol increased. Therefore, optimizing the conditions for the MIPMS synthesis is necessary to produce a sorbent with better selectivity.

Synthesis, characterization and absorption evaluation of bifunctional monomer magnetic molecularly imprinted polymers nanoparticles for the extraction of 6-benzylaminopurine from vegetables

An adsorbent-magnetic molecularly imprinted polymers nanoparticles (MMIPs NPs) were synthesized for the extraction of 6-benzylaminopurine (6-BA) using Fe₃O₄ as magnetic core. The MIPs were prepared with methacrylic acid and sodium p-styrene sulfonate as bifunctional monomers. The adsorbents were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis and vibrating sample magnetometer. The adsorption properties were evaluated by static, kinetic and selective adsorption experiments. The MMIPs NPs exhibit a high adsorption capacity (37.63 mg g^-1) and favorable imprinting factor (2.88) toward 6-BA. The chromatogram of 6-BA extraction using the MMIPs NPs as the adsorbent demonstrates that the matrix interference has been minimized. More importantly, MMIPs NPs can be applied to extracting 6-BA from mung bean sprout and cucumber with satisfactory recoveries (91.14-104.52%), and can be reused for at least five times. This work provides a new strategy to efficiently extract 6-BA from vegetables.

Molecular imprinting based electrochemical biosensor for identification of serum amyloid A (SAA), a neonatal sepsis biomarker

Neonatal septicemia is a bacterial infection in newborns. It is caused by bacteria including Escherichia coli and Group B Streptococcus (GBS). Neonatal septicemia is divided into early-onset and late-onset sepsis. The diagnosis of neonatal septicemia is a challenging task because of the presence of nonspecific symptoms. Biomarkers such as C-reactive protein (CRP), procalcitonin (PCT), and serum amyloid A (SAA) can help in the detection of sepsis at early stages. The level of biomarkers is elevated once sepsis occurs in the body. This study presents the development of an electrochemical biosensor based on nanomaterials integrated molecularly imprinted polymer technique. To obtain the synergistic effect and high conductivity, multi-walled carbon nanotubes (MWCNTs), manganese oxide nanospheres (MnO₂NSs), and cobalt oxide nanoparticles (Co₃O₄NPs) were coated over the screen-printed electrode (SPE). A further modification was done by polymerizing molecularly imprinted polymer (MIP) specifically synthesized for SAA onto modified SPE. The performance of the designed platform was evaluated through electrochemical techniques. The operating range of the developed sensor was found to be 0.01 pM to 1 μM and 0.01 pM as the lower detection limit.

Fabrication of a sensing platform for identification of tumor necrosis factor-alpha: a biomarker for neonatal sepsis

Neonatal sepsis is a prime cause of neonatal deaths across the globe. Presently, various medical tests and biodevices are available in neonatal care. These diagnosis platforms possess several limitations such as being highly expensive, time-consuming, or requiring skilled professionals for operation. These limitations can be overcome through biosensor development. This work discusses the assembling of an electrochemical sensing platform that is designed to detect the level of tumor necrosis factor-alpha (TNF-α). The sensing platform was moderated with nanomaterials molybdenum disulfide nanosheets (MoS₂NSs) and silicon dioxide-modified iron oxide nanoparticles (Fe₃O₄@SiO₂NPs). The integration of nanomaterials helps in accomplishing the improved characteristics of the biosensor in terms of conductivity, selectivity, and sensitivity. Further, the molecularly imprinted polymer (MIP) approach was incorporated for sensing the presence of TNF-α on the surface of the working electrode. The electrochemical response of the electrode was recorded at different conditions. A broad concentration range was selected to optimize the biosensor from 0.01 pM to 100 nM. The sensitivity of the biosensor was higher and it exhibits a lower detection limit (0.01 pM).

Fe(III)-Complex-Imprinted Polymers for the Green Oxidative Degradation of the Methyl Orange Dye Pollutant

One of the biggest problems worldwide is the pollution of natural water bodies by dyes coming from effluents used in the textile industry. In the quest for novel effluent treatment alternatives, the aim of this work was to immobilize Fe(III) complexes in molecularly imprinted polymers (MIPs) to produce efficient Fenton-like heterogeneous catalysts for the green oxidative degradation of the methyl orange (MO) dye pollutant. Different metal complexes bearing commercial and low-cost ligands were assayed and their catalytic activity levels towards the discoloration of MO by H2O2 were assessed. The best candidates were Fe(III)-BMPA (BMPA = di-(2-picolyl)amine) and Fe(III)-NTP (NTP = 3,3',3″-nitrilotripropionic acid), displaying above 70% MO degradation in 3 h. Fe(III)-BMPA caused the oxidative degradation through two first-order stages, related to the formation of BMPA-Fe-OOH and the generation of reactive oxygen species. Only the first of these stages was detected for Fe(III)-NTP. Both complexes were then employed to imprint catalytic cavities into MIPs. The polymers showed catalytic profiles that were highly dependent on the crosslinking agent employed, with N,N-methylenebisacrylamide (MBAA) being the crosslinker that rendered polymers with optimal oxidative performance (>95% conversion). The obtained ion-imprinted polymers constitute cheap and robust solid matrices, with the potential to be coupled to dye-containing effluent treatment systems with synchronous H2O2 injection.

Recognition of human hemoglobin with macromolecularly imprinted polymeric nanoparticles using non-covalent interactions

Hemoglobin (Hb) is the most abundant protein in the blood. It is vital for the living as oxygen carriers. Some of the very pure Hb-containing biological fluids are currently under clinical trial. However, the removal and purification of Hb from the blood are quite difficult, especially when it is at a low concentration level. In this study, the molecularly imprinted polymeric nanoparticles (MIPNs) were prepared using N-methacryloyl-histidine methyl ester (MAH) by mini-emulsion polymerization technique for specific binding of human hemoglobin (HHb). MIPNs in monosize form have a size of 152 ± 4 nm. They also have a high binding capacity (32.33 mg/g) of HHb. MIPNs retain 84% of the re-binding capacity for HHb after 10 cycles. The nanoparticles have 16 and 5 times higher binding capacity of HHb, respectively, in the presence of bovine serum albumin and lysozyme. Thanks to their high binding capacity and selectivity, MIPNs will allow them to be detected selectively for different target molecules. According to molecular docking, the main binding forces depend on hydrogen bonds and Van der Waals forces in the interaction within 5 Å around MAH molecule are observed through the amino acid residues of HHb at β1 and β2 subunit. The statistical mechanical analysis of docking showed that the free energy (ΔG) is -2732.14 kcal/mol, which indicates the interaction between MAH and HHb is energetically favorable at 298.15°K.

Removal of bisphenol A from aqueous media using a highly selective adsorbent of hybridization cyclodextrin with magnetic molecularly imprinted polymer

In this study, a unique magnetic molecularly imprinted polymer (MMIP) adsorbent towards bisphenol A (BPA) as a template molecule was developed by bulk polymerization using β-cyclodextrin (β-CD) as a co-monomer with methacrylic acid (MAA) to form MMIP MAA-βCD as a new adsorbent. β-CD was hybridized with MAA to obtain water-compactible imprinting sites for the effective removal of BPA from aqueous samples. Benzoyl peroxide and trimethylolpropane trimethacrylate were used as the initiator and cross-linker, respectively. The adsorbents were characterized by Fourier transform infrared spectroscopy, scanning electronic microscopy, transmission electron microscopy, vibrating sample magnetometer, Brunauer-Emmett-Teller and X-ray diffraction. 1H nuclear magnetic resonance spectroscopy was used to characterize the MAA-βCD and BPA-MAA-βCD complex. Several parameters influencing the adsorption efficiency of BPA such as adsorbent dosage, pH of sample solution, contact time, initial concentrations and temperature as well as selectivity and reusability study have been evaluated. MMIP MAA-βCD showed significantly higher removal efficiency and selective binding capacity towards BPA compared to MMIP MAA owing to its unique morphology with the presence of β-CD. The kinetics data can be well described by the pseudo second-order kinetic and Freundlich isotherm and Halsey models best fitted the isotherm data. The thermodynamic studies indicated that the adsorption reaction was a spontaneous and exothermic process. Therefore, MMIP based on the hybrid monomer of MAA-βCD shows good potential of a new monomer in molecularly imprinted polymer preparation and can be used as an effective adsorbent for the removal of BPA from aqueous solutions.

Computer simulation aided preparation of molecularly imprinted polymers for separation of bilobalide

In this study, the preparation of molecularly imprinted polymers for bilobalide (BBMIPs) was successfully achieved by bulk polymerization with methacrylamide (MAM), trimethylolpropane triacrylate (TMPTA), and acetonitrile (ACN) as functional monomer, cross-linker, and solvent, respectively. After Gaussian software simulation and single factor experiments, the prepared MIPs with a molar ratio of 1:4:15 for BB-MAM-TMPTA were systematically characterized. The hydrogen bonding interaction between BB and MAM was confirmed by a combination of FTIR and NMR analysis. Thermal gravimetric analysis results displayed that MIPs have excellent thermal stability under high temperature. Additionally, the average pore size and surface area of MIPs were found to be higher than those of NIPs through nitrogen adsorption results. The results of static adsorption and kinetic adsorption suggested that the adsorption equilibrium concentration was 0.6 mg/mL and the equilibrium time was 5 h, and the Langmuir and pseudo-second-order kinetic models were proven to fit with static and kinetic adsorption behaviors, respectively. Meanwhile, the selective adsorption study revealed that MIPs show high adsorption and great selectivity towards BB in comparison with other substances having similarly structure. MIPs also possessed a good performance on reusability, maintaining a high recovery rate after being reused 5 times. The application experiment further indicated that MIPs can effectively separate BB from low purity samples. Therefore, the prepared MIPs had a great potential for BB separation.

Theoretical Insight into the Interaction between Chloramphenicol and Functional Monomer (Methacrylic Acid) in Molecularly Imprinted Polymers

Molecular imprinting technology is a promising method for detecting chloramphenicol (CAP), a broad-spectrum antibiotic with potential toxicity to humans, in animal-derived foods. This work aimed to investigate the interactions between the CAP as a template and functional monomers required for synthesizing efficient molecularly imprinted polymers for recognition and isolation of CAP based on density functional theory. The most suitable monomer, methacrylic acid (MAA), was determined based on interaction energies and Gibbs free energy changes. Further, the reaction sites of CAP and MAA was predicted through the frontier molecular orbitals and molecular electrostatic potentials. Atoms in molecules topology analysis and non-covalent interactions reduced density gradient were applied to investigate different types of non-covalent and inter-atomic interactions. The simulation results showed that CAP was the main electron donor, while MAA was the main electron acceptor. Moreover, the CAP–MAA complex simultaneously involved N-H···O and C=O···H double hydrogen bonds, where the strength of the latter was greater than that of the former. The existence of hydrogen bonds was also confirmed by theoretical and experimental hydrogen nuclear magnetic resonance and Fourier transform infrared spectroscopic analyses. This research can act as an important reference for intermolecular interactions and provide strong theoretical guidance regarding CAP in the synthesis of molecularly imprinted polymers.

Evaluation of Molecularly Imprinted Polymers for Point-of-Care Testing for Cardiovascular Disease

Molecular imprinting is a rapidly growing area of interest involving the synthesis of artificial recognition elements that enable the separation of analyte from a sample matrix and its determination. Traditionally, this approach can be successfully applied to small analyte (<1.5 kDa) separation/ extraction, but, more recently it is finding utility in biomimetic sensors. These sensors consist of a recognition element and a transducer similar to their biosensor counterparts, however, the fundamental distinction is that biomimetic sensors employ an artificial recognition element. Molecularly imprinted polymers (MIPs) employed as the recognition elements in biomimetic sensors contain binding sites complementary in shape and functionality to their target analyte. Despite the growing interest in molecularly imprinting techniques, the commercial adoption of this technology is yet to be widely realised for blood sample analysis. This review aims to assess the applicability of this technology for the point-of-care testing (POCT) of cardiovascular disease-related biomarkers. More specifically, molecular imprinting is critically evaluated with respect to the detection of cardiac biomarkers indicative of acute coronary syndrome (ACS), such as the cardiac troponins (cTns). The challenges associated with the synthesis of MIPs for protein detection are outlined, in addition to enhancement techniques that ultimately improve the analytical performance of biomimetic sensors. The mechanism of detection employed to convert the analyte concentration into a measurable signal in biomimetic sensors will be discussed. Furthermore, the analytical performance of these sensors will be compared with biosensors and their potential implementation within clinical settings will be considered. In addition, the most suitable application of these sensors for cardiovascular assessment will be presented.

Towards A New Approach for the Description of Cyclo⁻2,4-Dihydroxybenzoate, A Substance Which Effectively Mimics Zearalenone in Imprinted Polymers Designed for Analyzing Selected Mycotoxins in Urine

A method of purifying cyclododecyl 2,4-dihydroxybenzoate as a potential replacement template molecule for preparation of molecularly-imprinted polymers for isolation of zearalenone in urine was developed. Full physicochemical characteristics of cyclododecyl 2,4-dihydroxybenzoate for the first time included crystallographic analysis and molecular modelling, which made possible the determination of the similarity between the cyclododecyl 2,4-dihydroxybenzoate and zearalenone molecules. The obtained molecularly-imprinted polymers show very high in vitro selectivity towards zearalenone due to specific interactions (e.g., hydrogen bonding, molecular recognition interaction). The achieved extraction recovery exceeds 94% at the tested concentration levels (20–500 ng·mL⁻¹) with a relative standard deviation below 2%. Immunosorbents were found to have lower recoveries (below 92.5%) and RSD value between 2 and 4% for higher concentrations of the studied substance (400 ng·mL⁻¹).

Fabrication of Core-Shell Magnetic Molecularly Imprinted Nanospheres towards Hypericin via Click Polymerization

The core-shell structure molecularly imprinted magnetic nanospheres towards hypericin (Fe₃O₄@MIPs) were prepared by mercapto-alkyne click polymerization. The shape and size of nanospheres were characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The nanospheres were analyzed by FTIR spectroscopy to verify the thiol-yne click reaction in the presence or absence of hypericin. The Brunauer⁻Emmet⁻Teller (BET) method was used for measuring the average pore size, pore volume and surface area. The Fe₃O₄@MIPs synthesized displayed a good adsorption capacity (Q = 6.80 µmol·g-1). In addition, so-prepared Fe₃O₄@MIPs showed fast mass transfer rates and good reusability. The method established for fabrication of Fe₃O₄@MIPs showed excellent reproducibility and has broad potential for the fabrication of other core-shell molecularly imprinted polymers (MIPs).

Theoretical and experimental research on self-assembly system of molecularly imprinted polymers formed via chloramphenicol and methacrylic acid

Chloramphenicol was chosen as the imprinting molecule and the methacrylic acid was chosen as the functional monomer to prepare molecularly imprinted polymers. Ethylene glycol dimethacrylate, pentaerythritol triacrylate, and trimethylolpropane trimethylacrylate were used as the cross-linking agents, respectively. The interaction processes between chloramphenicol and methacrylic acid were simulated by using the ωB97XD/6-31G (d,p) method. The self-assembled configuration, bonding sites, binding number, binding energy, and interaction principle of stable complex formed by chloramphenicol and methacrylic acid with different molar ratios have been studied. The selectivity of the most stable complex formed from chloramphenicol and methacrylic acid was discussed with the thiamphenicol and florfenicol as the analogues of chloramphenicol. The results showed that chloramphenicol and methacrylic acid were interacted through the hydrogen bonds. When the molar ratio was 1:10 and pentaerythritol triacrylate as the cross-linking agent, the ordered complex formed by chloramphenicol and methacrylic acid has the largest amount of hydrogen bonds and the lowest binding energy. Scatchard analysis showed that the maximum apparent adsorption capacity was 173.3 mg/g (0.536 mol/g), and the selection factor of florfenicol was the largest. This study provides a reliable theoretical and experimental basis for the design, preparation, and characterization of chloramphenicol molecularly imprinted polymers.

The Multi-Template Molecularly Imprinted Polymer Based on SBA-15 for Selective Separation and Determination of Panax notoginseng Saponins Simultaneously in Biological Samples

The feasible, reliable and selective multi-template molecularly imprinted polymers (MT-MIPs) based on SBA-15 (SBA-15@MT-MIPs) for the selective separation and determination of the trace level of ginsenoside Rb₁ (Rb₁), ginsenoside Rg₁ (Rg₁) and notoginsenoside R₁ (R₁) simultaneously from biological samples were developed. The polymers were constructed by SBA-15 as support, Rb₁, Rg₁, R₁ as multi-template, acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The new synthetic SBA-15@MT-MIPs were satisfactorily applied to solid-phase extraction (SPE) coupled with high performance liquid chromatography (HPLC) for the separation and determination of trace Rb₁, Rg₁ and R₁ in plasma samples. Under the optimized conditions, the limits of detection (LODs) and quantitation (LOQs) of the proposed method for Rb₁, Rg₁ and R₁ were in the range of 0.63⁻0.75 ng·mL-1 and 2.1⁻2.5 ng·mL-1, respectively. The recoveries of R₁, Rb₁ and Rg₁ were obtained between 93.4% and 104.3% with relative standard deviations (RSDs) in the range of 3.3⁻4.2%. All results show that the obtained SBA-15@MT-MIPs could be a promising prospect for the practical application in the selective separation and enrichment of trace Panax notoginseng saponins (PNS) in the biological samples.

Preparation and Evaluation of Core⁻Shell Magnetic Molecularly Imprinted Polymers for Solid-Phase Extraction and Determination of Sterigmatocystin in Food

Magnetic molecularly imprinted polymers (MMIPs), combination of outstanding magnetism with specific selective binding capability for target molecules, have proven to be attractive in separation science and bio-applications. Herein, we proposed the core⁻shell magnetic molecularly imprinted polymers for food analysis, employing the Fe₃O₄ particles prepared by co-precipitation protocol as the magnetic core and MMIP film onto the silica layer as the recognition and adsorption of target analytes. The obtained MMIPs materials have been fully characterized by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), vibrating sample magnetometer (VSM), and re-binding experiments. Under the optimal conditions, the fabricated Fe₃O₄@MIPs demonstrated fast adsorption equilibrium, a highly improved imprinting capacity, and excellent specificity to target sterigmatocystin (ST), which have been successfully applied as highly efficient solid-phase extraction materials followed by high-performance liquid chromatography (HPLC) analysis. The MMIP-based solid phase extraction (SPE) method gave linear response in the range of 0.05⁻5.0 mg·L-1 with a detection limit of 9.1 µg·L-1. Finally, the proposed method was used for the selective isolation and enrichment of ST in food samples with recoveries in the range 80.6⁻88.7% and the relative standard deviation (RSD) <5.6%.

Fabrication of Hypericin Imprinted Polymer Nanospheres via Thiol-Yne Click Reaction

To fabricate molecularly imprinted polymer nanospheres via click reaction, five different clickable compounds were synthesized and two types of click reactions (azide-alkyne and thiol-yne) were explored. It was found that molecularly imprinted polymer nanospheres could be successfully synthesized via thiol-yne click reaction using 3,5-diethynyl-pyridine (1) as the monomer, tris(3-mercaptopropionate) (tri-thiol, 5) as the crosslinker, and hypericin as the template (MIP⁻NSHs). The click polymerization completed in merely 4 h to produce the desired MIP⁻NSHs, which were characterized by FTIR, SEM, DLS, and BET, respectively. The reaction conditions for adsorption capacity and selectivity towards hypericin were optimized, and the MIP⁻NSHs synthesized under the optimized conditions showed a high adsorption capacity (Q = 6.03 μmol•g-1) towards hypericin. The imprinting factors of MIP⁻NSHs towards hypericin, protohypericin, and emodin were 2.44, 2.88, and 2.10, respectively.

Upconversion Nanophosphor-Involved Molecularly Imprinted Fluorescent Polymers for Sensitive and Specific Recognition of Sterigmatocystin

Originated from the bottom-up synthetic strategy, molecularly imprinted polymers (MIPs) possess the inherent ability of selective and specific recognition and binding of the target analytes, with their structural cavities that can match the target molecules in respect to size, shape, and functional groups. Herein, based on the high selectivity of MIPs and the fluorescence properties of the β-NaYF₄:Yb3+, Er3+ upconversion nanoparticles, MIPs with both specificity and fluorescent signals are fabricated to recognize trace sterigmatocystin (ST) with high selectivity and sensitivity. The structure analogue of ST, 1,8-dihydroxyanthraquinone (DT), was employed as the template molecule, acrylamide as the functional monomer, 3-methacryloyloxypropyltrimethoxysilane as the crosslinking agent, and a new molecular imprinting technique of non-aqueous sol-gel method is used to synthesize a molecularly imprinted material with high selectivity to ST. Under optimal conditions, the fluorescence enhancement of fluorescent MIPs increased as the concentration of ST increased. In the range of 0.05⁻1.0 mg L-1, fluorescence enhancement and the concentration showed a good linear relationship with a detection limit of 0.013 mg L-1. Real sample analysis achieved the recoveries of 83.8⁻88.8% (RSD 5.1%) for rice, 82.1⁻87.5% (RSD 4.6%) for maize, and 80.6⁻89.2% (RSD 3.0%) for soybeans, respectively, revealing the feasibility of the developed method.

A Facile Approach for Fabrication of Core-Shell Magnetic Molecularly Imprinted Nanospheres towards Hypericin

By taking advantage of the self-polymerization of dopamine on the surface of magnetic nanospheres in weak alkaline Tris-HCl buffer solution, a facile approach was established to fabricate core-shell magnetic molecularly imprinted nanospheres towards hypericin (Fe₃O₄@PDA/Hyp NSs), via a surface molecular imprinting technique. The Fe₃O₄@PDA/Hyp NSs were characterized by FTIR, TEM, DLS, and BET methods, respectively. The reaction conditions for adsorption capacity and selectivity towards hypericin were optimized, and the Fe₃O₄@PDA/Hyp NSs synthesized under the optimized conditions showed a high adsorption capacity (Q = 18.28 mg/g) towards hypericin. The selectivity factors of Fe₃O₄@PDA/Hyp NSs were about 1.92 and 3.55 towards protohypericin and emodin, respectively. In addition, the approach established in this work showed good reproducibility for fabrication of Fe₃O₄@PDA/Hyp.

A battle between spherical and cube-shaped Ag/AgCl nanoparticle modified imprinted polymer to achieve femtogram detection of alpha-feto protein

In this work, a sensitive and selective molecularly imprinted polymer modified electrochemical sensor was developed for the detection of the hepatocellular carcinoma (HCC) biomarker, alpha feto protein (AFP) on the surface of specifically designed Ag/AgCl nanoparticles. Herein, for the first time, the effect of the shape of nanoparticles on the behavior of an imprinted polymer was studied using cube- and spherical-shaped Ag/AgCl nanoparticles. It was found that cube-shaped nanoparticles have high surface to volume ratios and higher electrocatalytic activity, and are, therefore, a suitable platform for the synthesis of imprinted polymers. Herein, we have demonstrated how a change in the morphology of the nanomaterials can affect the electrochemical and adsorption properties of an imprinted polymer towards the target analyte (here, AFP). A cube-shaped nanoparticle@imprinted polymer was used for the fabrication of the electrochemical sensor, the analytical performance of which was shown, by a square wave stripping voltammetric technique, to be good for the detection of AFP. The current response of the electrochemical sensor was linear for AFP concentrations in the range from 0.10 to 700.0 pg mL-1, with an ultra trace detection limit of 24.6 fg mL-1. This sensor offers high selectivity, sensitivity, simplicity and clinical applicability for AFP determination in human blood serum, plasma, and urine, without using antibodies or any biological components, this has not been reported for previously reported systems. The proposed sensor has the potential to be used as an alternative to the commercially available, costly, sophisticated enzyme-linked immunosorbent assay kits for AFP determination.

Molecularly Imprinted Polymers for the Identification and Separation of Chiral Drugs and Biomolecules

Molecularly imprinting polymers (MIPs) have been extensively applied in chromatography for the separation of chiral drugs. In this review, we mainly summarize recent developments of various MIPs used as chiral stationary phases (CSPs) in high performance liquid chromatography (HPLC), capillary electrochromatography (CEC), and supercritical fluid chromatography (SFC). Among them, HPLC has the advantages of straightforward operation and high selectivity. However, the low separation efficiency, due to slow interaction kinetics and heavy peak broadening, is the main challenge for the application of MIPs in HPLC. On the other hand, CEC possesses both the high selectivity of HPLC and the high efficiency of capillary electrophoresis. In CEC, electroosmotic flow is formed across the entire column and reduces the heavy peak broadening observed in HPLC mode. SFC can modify the low interaction kinetics in HPLC when supercritical fluids are utilized as mobile phases. If SFC and MIP-based CSPs can be well combined, better separation performance can be achieved. Particles, monoliths and membrane are typical formats of MIPs. Traditional MIP particles produced by bulk polymerization have been replaced by MIP particles by surface imprinting technology, which are highly consistent in size and shape. Monolithic MIPs are prepared by in situ method in a column, greatly shortening the pre-preparation time. Some novel materials, such as magnetic nanoparticles, are integrated into the MIPs to enhance the controllability and efficiency of the polymerization. This review will be helpful to guide the preparation, development, and application of MIPs in chromatographic and electrophoretic enantioseparation.

Removal of toxic mercury from petroleum oil by newly synthesized molecularly-imprinted polymer

In recent years, molecularly-imprinted polymers (MIPs) have attracted the attention of several researchers due to their capability for molecular recognition, easiness of preparation, stability and cost-effective production. By taking advantage of these facts, Hg(II) imprinted and non-imprinted copolymers were prepared by polymerizing mercury nitrate stock solution (or without it) with methacrylic acid (MAA), 2-hydroxyl ethyl methacrylate (HEMA), methanol and ethylene glycol dimethacrylate (EGDMA) as the monomer, co-monomer solvent (porogen) and cross-linker, respectively. Thus, the formed Hg(II) imprinted polymer was characterized by using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer, Emmett and Teller (BET) and thermal gravimetric analysis (TGA). The separation and preconcentration characteristics of Hg(II) imprinted polymer were investigated by solid phase extraction (SPE) procedures, and an optimal pH of 7 was investigated as ideal. The specific surface area of the Hg(II) imprinted polymer was found to be 19.45 m²/g with a size range from 100 to 140 µm in diameter. The maximum adsorption capacity was observed to be 1.11 mg/g of Hg(II) imprinted beads with 87.54% removal of Hg(II) ions within the first 5 min. The results of the study therefore confirm that the Hg(II) imprinted polymer can be used multiple times without significantly losing its adsorption capacity.

Molecularly imprinted solid phase extraction coupled to high performance liquid chromatography for determination of aflatoxin M1 and B1 in foods and feeds

Molecularly imprinted solid phase extraction for determination of aflatoxin M₁ and B₁ in foods and feeds.

Mesoporous molecularly imprinted polymer nanoparticles as a sustained release system of azithromycin

A combination of a molecular imprinting technique and precipitation polymerization was applied to develop novel azithromycin-imprinted poly(methacrylic acid-co-ethylene glycol dimethacrylate) nanoparticles for sustained release of azithromycin (AZM).