Novel monodisperse molecularly imprinted shell for estradiol based on surface imprinted hollow vinyl-SiO2 particles

Fabrication of Highly Sensitive and Selective Nitrite Colorimetric Sensor Based on the Enhanced Peroxidase Mimetic Activity of Using Acetic Acid Capped Zinc Oxide Nanosheets

Nitrite ions (NO2-), as one of the leading type-A inorganic-anion, showing significant-effects in the aquatic environment and also to humans health. Whereas, the higher uptake causes detrimental threat to human health leading to various chronic diseases, thus demanding efficient, reliable and convenient method for its monitoring. For this purpose, in the present research study we have fabricated the mimetic nonozyme like catalyst based colorimetric nitrite sensor. The acetic acid capped Zinc Oxide (ZnO) nanosheets (NSs) were introduce as per-oxidase mimetic like catalyst which shows high efficiency towards the oxidative catalysis of colorless tetramethylbenzidine (TMB) to oxidized-TMB (blue color) in the presence of Hydrogen-peroxide (H2O2). The present nitrite ions will stimulate the as formed oxidized-TMB (TMBox), and will caused diazotization reaction (diazotized-TMBox), which will not only decreases the peak intensity of UV-visible peak of TMBox at 652 nm but will also produces another peak at 446 nm called as diazotized-TMBox peak, proving the catalytic reaction between the nitrite ions and TMBox. Further, the prepared colorimetric sensor exhibits better sensitivity with a wider range of concentration (1 × 10-3-4.50 × 10-1 µM), lowest limit of detection (LOD) of 0.22 ± 0.05 nM and small limit of quantification (LOQ) 0.78 ± 0.05 nM having R2 value of 0.998. Further, the colorimetric sensor also manifest strong selectivity towards NO2- as compared to other interference in drinking water system. Resultantly, the prepared sensor with outstanding repeatability, stability, reproducibility, re-usability and its practicability in real water samples also exploit its diverse applications in food safety supervision and environmental monitoring.

Preparation of metal-organic framework @molecularly imprinted polymers for extracting N-nitrosamines in salted vegetables

In this paper, the novel metal-organic framework @molecularly imprinted polymers were prepared and applied in extracting N-nitrosamines from salted vegetables. The imprinted polymers were coated on the surface of MIL-101 using multi-dummy template molecules (5-nonanol, benzhydrol and N-formylpyrrolidine). The characterization and adsorbing experiments showed that the hybrid imprinted polymers presented spherical particles with typically core-shell structure, and exhibited high adsorption capacity (maximum capacity: 46.85 mg/g) and fast equilibrium rate (only 5 min) for N-nitrosamines. Various parameters (sample loading solvent, pH, washing solvent, elution solvent and elution volume) affecting solid-phase extraction were optimized. Under the optimum conditions, the solid-phase extraction process based on the hybrid polymers combined with high performance liquid chromatography-ultraviolet detection method was established and applied to analyze N-nitrosamines in different salted vegetables. The results showed that the developed method produced the linear relationship between the peak areas versus the N-nitrosamines concentrations of 0.2-10 µg/g with limit of detections from 20.6 to 76.1 ng/g. The spiked recovery of N-nitrosamines in the salted vegetable samples was in the range of 66-100.5 % with relative standard deviation from 0.1 to 3.4 %. Those results demonstrated that the established method was sensitive and efficient for directly enriching and analyzing trace N-nitrosamines in salted vegetables.

Honeycomb-like 3D ordered macroporous SiOx/C nanoarchitectures with carbon coating for high-performance lithium storage

SiOx anodes are garnering significant interest in lithium-ion batteries (LIBs) due to theirs low voltage plateau and high capacity. However, critical drawbacks, including high expansion rate and low electronic conductivity, severely limit their practical applications. While 0D, 1D, and 2D scale nanostructures have been proven to mitigate these issues, these materials tend to accumulate after prolonged cycling, leading to adverse effects on the mass transfer processes within the electrode. Herein, we have developed a honeycomb-like SiOx/C nanoarchitecture with carbon coating based on a 3D ordered macroporous (3DOM) structure. The 3D interconnected pore windows facilitate the diffusion and transport of lithium ions (Li+) in the electrolyte, and the extremely thin walls (<15 nm) provide a shorter transport path for Li+ in the solid. The carbon cladding buffers volume expansion and enhances electronic conductivity. The as-prepared anode demonstrates a high reversible capacity of 1068 mAh/g and an initial coulombic efficiency of 70.7 %. It maintains a capacity of 644 mAh/g (capacity retention of 84.63 %) even at a high current of 1.0 A/g after 700 cycles. The unique honeycomb-like structure offers enormous insights into the study of energy storage in 3D materials.

Determination of Organophosphate Esters in Water Samples Using Gas Chromatography– Mass Spectrometry (GC–MS) and Magnetic Solid-Phase Extraction (SPE) Based on Multi-Walled Carbon Nanotubes (MWCNTs)

A method based on gas chromatography–mass spectrometry (GC–MS), coupled with magnetic solid-phase extraction (SPE) with multi-walled carbon-nanotube (MWCNT)-coated iron oxide (Fe3O4) as the adsorbent, was developed for analyzing four organophosphate esters in ambient water samples. The magnetic, MWCNT composites were prepared by hydrothermal synthesis and characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and superconducting quantum interference device magnetometry (SQUID). The extraction and desorption conditions, such as adsorbent dosage, adsorption time, eluent type, and eluent volume, were studied. The adsorbent was used to extract analytes within 50 min. The limit of detection (LOD) was between 0.038–1 μg/L, and the limit of quantitation (LOQ) was between 0.10–3.59 μg/L. The method was applied to analyze organophosphate esters in environmental water samples. A 72.5–89.1% recovery was obtained by analyzing spiked samples with low-, medium-, and high-concentration analytes. The relative standard deviations (RSDs) were less than 10%. This method displayed better sensitivity and accuracy; therefore, it could be successfully used to detect organophosphate esters in environmental water samples.

Hollow porous molecularly imprinted polymers as emerging adsorbents

Hollow porous molecularly imprinted polymers (HPMIPs) are identified as promising adsorbents with many advantageous properties (e.g., large number of imprinted cavities, highly accessible binding sites, controllable pore structure, and fast mass transfer). Because of such properties, HPMIPs can exhibit improved binding capacity and kinetics to make analyte molecules readily interact with a greater number of recognition sites on the imprinted shell. This review highlights the synthesis and utility of HPMIPs as adsorbents to cover diverse targets of interest (e.g., endocrine disrupting chemicals, pharmaceuticals, pesticides, and heavy metal ions). The overall potential of HPMIPs is thus discussed in the context of analytical chemistry with particular focus on the efficient extraction of trace-level targets from complex matrices.

Assessment of cross-reactivity in a tailor-made molecularly imprinted polymer for phenolic compounds using four adsorption isotherm models

Cross-reactivity is an important feature of molecularly imprinted polymers (MIPs), and is central to successful use of a pseudo-template in molecular imprinting. The adsorption and cross-reactivity of a molecularly imprinted polymer (MIP) designed for recognition of phenols from water was assessed using four different isotherm models (Langmuir (LI), Freundlich (FI), Langmuir-Freundlich (L-FI), and Brunauer, Emmett, and Teller (BET)). The L-FI model succeeded in explaining the cross-reactivity behavior through the total number of binding sites, the affinity constants and heterogeneity indices of the small phenols (phenol (ph), 2-methylphenol (2-MP), 3-methylphenol (3-MP), 2-chlorophenol (2-CP), 2,4-dimethylphenol (DMP), 2,4-dichlorophenol (DCP), 4-chloro-3-methylphenol (CMP)) with evidence that the phenols compete for binding sites based on their hydrophobicity as well as π-π, π-σ and dipole-dipole intermolecular forces. The recognition of the large phenols (2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP), 4-teroctylphenol (4-OP), 4-nonylphenol (4-NP), which have much higher binding affinities than the smaller phenolic compounds, was explained with the BET isotherm model that predicts that multiple layers adsorb to the adsorbed monolayer. The adsorption behavior with MIPs is also shown to be superior to corresponding non-imprinted polymers and applicability of MIPs for trace analysis is highlighted.

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 the detection of 17β-estradiol in food matrices: A review

Pollution of endocrine disrupting chemicals has become a global issue. As one of the hormonally active compounds, 17β-estradiol produces the strongest estrogenic effect when it enters the organism exogenously including food intakes, bringing potential harmfulness such as malfunction of the endocrine system. Therefore, in order to assure food safety and avoid potential risks of 17β-estradiol to humans, it is of great significance to develop rapid, sensitive and selective approaches for the detection of 17β-estradiol in food matrices. In this review, the harmfulness and main sources of 17β-estradiol are firstly introduced, followed by the description of the principles and applications of different approaches for 17β-estradiol detection including high performance liquid chromatography, electrochemistry, Raman spectroscopy, fluorescence and colorimetry. Particularly, applications in detecting 17β-estradiol in food matrices over the years of 2010-2018 are discussed. Finally, advantages and limitations of these detection methods are highlighted and perspectives on future developments in the detection methods for 17β-estradiol are also proposed. Although many detection approaches can achieve trace or ultratrace detection of 17β-estradiol, further studies should be focused on the development of in-situ and real-time methods to monitor and evaluate 17β-estradiol for food safety.

A study on the preparation and application of a core-shell surface imprinted uranyl magnetic chelating adsorbent

A core-shell surface imprinted uranyl magnetic chelating adsorbent (UMCA) was synthesized by combining the sol-gel process with the surface molecular imprinting technique (SMIT). A specific salophen and uranyl-salophen were designed and synthesized. Then, the synthesized uranyl-salophen complex was used as a template (in which uranyl is the target analyte), 3-aminopropyltriethoxysilane as a functional monomer and tetraethylorthosilicate as a cross-linker. The obtained UMCA was characterized by a variety of modern analytical and detection techniques. The adsorbent can be used for the solid-phase extraction of uranyl with good selectivity, high adsorption capacity, magnetic separation characteristics and good reusability. The chelating sorbent was successfully applied for the separation of uranyl, followed by multiphase photocatalytic resonance fluorescence method determination in several environmental water samples with a relative standard deviation of <5.48% and spiked recoveries of 92.5% to 103.0%. The adsorption mechanism was preliminarily discussed.

An ultrasensitive chemiluminescence aptasensor for thrombin detection based on iron porphyrin catalyzing luminescence desorbed from chitosan modified magnetic oxide graphene composite

In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe₃O₄@GO). Firstly, CS@Fe₃O₄@GO was prepared. CS@Fe₃O₄@GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe₃O₄. GO, Fe₃O₄ and CS@Fe₃O₄@GO were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). Then, thrombin aptamer (T-Apt) and hemin (HM, an iron porphyrin) were sequentially modified on the surface of CS@Fe₃O₄@GO to form CS@Fe₃O₄@GO@T-Apt@HM. The immobilization properties of CS@Fe₃O₄@GO to T-Apt and adsorption properties of CS@Fe₃O₄@GO@T-Apt to HM were sequentially researched through the curves of kinetics and the curves of thermodynamics. When thrombin existed in solutions, HM was desorbed from the surface of CS@Fe₃O₄@GO@T-Apt@HM owing to the strong specific recognition ability between thrombin and T-Apt, causing the changes of CL signal. Under optimized CL conditions, thrombin could be measured with the linear concentration range of 5.0×10^-15-2.5×10^-10mol/L. The detection limit was 1.5×10^-15mol/L (3δ) while the relative standard deviation (RSD) was 3.2%. Finally, the CS@Fe₃O₄@GO@T-Apt@HM-CL aptasensor was used for the determination of thrombin in practical serum samples and recoveries ranged from 95% to 103%. Those satisfactory results revealed potential application of the CS@Fe₃O₄@GO@T-Apt@HM-CL aptasensor for thrombin detection in monitoring and diagnosis of human blood diseases.

Data-driven nanomechanical sensing: specific information extraction from a complex system

Smells are known to be composed of thousands of chemicals with various concentrations, and thus, the extraction of specific information from such a complex system is still challenging. Herein, we report for the first time that the nanomechanical sensing combined with machine learning realizes the specific information extraction, e.g. alcohol content quantification as a proof-of-concept, from the smells of liquors. A newly developed nanomechanical sensor platform, a Membrane-type Surface stress Sensor (MSS), was utilized. Each MSS channel was coated with functional nanoparticles, covering diverse analytes. The smells of 35 liquid samples including water, teas, liquors, and water/EtOH mixtures were measured using the functionalized MSS array. We selected characteristic features from the measured responses and kernel ridge regression was used to predict the alcohol content of the samples, resulting in successful alcohol content quantification. Moreover, the present approach provided a guideline to improve the quantification accuracy; hydrophobic coating materials worked more effectively than hydrophilic ones. On the basis of the guideline, we experimentally demonstrated that additional materials, such as hydrophobic polymers, led to much better prediction accuracy. The applicability of this data-driven nanomechanical sensing is not limited to the alcohol content quantification but to various fields including food, security, environment, and medicine.

Synthesis of magnetic molecularly imprinted polymers with excellent biocompatibility for the selective separation and inhibition of testosterone in prostate cancer cells

PURPOSE

Androgen plays an important role in the progression of prostate cancer. In the present study, novel magnetic molecularly imprinted polymers (MMIPs) with good biocompatibility were produced for the selective separation and inhibition of testosterone in prostate cancer cells.

MATERIALS AND METHODS

MMIPs were prepared by using magnetic nanospheres, gelatin, and testosterone as the supporting materials, functional monomer, and the template molecule, respectively. The characterization of the resultant products was investigated by transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry. To test whether MMIPs can remove testosterone in biologic samples, human LNCaP (androgen-dependent) and C4-2 (androgen-independent) prostate cancer cells were selected as cell models. The translocation of androgen receptor (AR) was detected by immunofluorescence assay, and the expression of PSA mRNA was detected by real-time quantitative polymerase chain reaction analysis. Cell flow cytometry analysis was performed to detect cell cycle arrest.

RESULTS

The synthesized nanomaterials (MMIPs) possessed high crystallinity, satisfactory superparamagnetic properties, and uniform imprinted shell, and exhibited high adsorption capacity, fast kinetics, and high selectivity for testosterone. Moreover, the obtained imprinted nanomaterials could selectively enrich and detect testosterone in the LNCaP cell samples as a solid-phase extractant coupled with high-performance liquid chromatography. In addition, the MMIPs could freely enter prostate cancer cells and suppress the translocation of AR into the cell nucleus. We further found that MMIPs inhibited upregulation of AR downstream target genes in LNCaP and C4-2 cells; also, MMIPs inhibited cell growth and induced obvious cell cycle arrest in androgen-dependent LNCaP cells, but had no obvious effect on androgen-independent C4-2 cells.

CONCLUSION

Our results indicate that the obtained imprinted nanomaterials can specifically and effectively bind testosterone and recover it from prostate cancer cells. Moreover, the MMIPs can freely enter prostate cancer cells and block the activation of testosterone-AR pathway. Thus, the MMIPs may be a new option for antiandrogen therapy in prostate cancer.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given.

Boronate-affinity hollow molecularly imprinted polymers for the selective extraction of nucleosides

Preparation of a boronate-affinity hollow molecularly imprinted polymer and its application as an SPE adsorbent for the selective enrichment of nucleosides.

Simultaneous selective extraction of nitramine explosives using molecularly imprinted polymer hollow spheres from post blast samples

Solvents modulate the adsorption selectivity and adsorption capacity of a molecularly imprinted polymer to target compounds.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Preparation of surface-imprinted microspheres effectively controlled by orientated template immobilization using highly cross-linked raspberry-like microspheres for the selective recognition of an immunostimulating peptide

Surface-imprinted microspheres were prepared using raspberry-like microspheres for selectively recognizing IHH.

Magnetic two-dimensional molecularly imprinted materials for the recognition and separation of proteins

We report a novel design of magnetic two-dimensional molecularly imprinted polymers on Fe₃O₄@GO for the high recognition and separation of proteins.

Water-compatible magnetic imprinted nanoparticles served as solid-phase extraction sorbents for selective determination of trace 17beta-estradiol in environmental water samples by liquid chromatography

Endocrine disrupting compounds (EDCs) are a potential risk for wildlife and humans for their existence in water. The efficient extraction and clean-up steps are required before detection of low concentration levels of EDCs. In this work, a novel water-compatible magnetic molecularly imprinted nanoparticles is synthesized for the selective extraction of 17β-estradiol (E2) in environmental water samples. The preparation is carried out by introducing aldehyde groups to the surface of amino-functionalized magnetic nanoparticles through a simple one-step modification, followed by copolymerization of functional monomer gelatin and template E2 via surface imprinting technique. The gelatin with abundant active groups could not only act as functional monomer reacting with template, but also assemble covalently at the surface of magnetic nanoparticles. At the same time, gelatin would improve the water-compatibility of imprinted materials for attaining high extraction efficiency. To obtain high imprinting effect, the preparation conditions are optimized in detail using Central composite design-response surface methodology. The resultant polymers have uniform spherical shape with a shell thickness of about 8nm, stable crystalline form, and super-paramagnetic property. Meanwhile, the obtained polymers have high capacity of 12.87mgg(-1) and satisfactory selectivity to template molecule. To testify the feasibility of the magnetic imprinted polymers in sample pretreatment, a method for determination of trace E2 in environmental water samples was set up by combination of solid-phase extraction (SPE) using the prepared polymers as sorbents and HPLC for rapid isolation and determination of E2. The limit of detection of proposed method is 0.04ngmL(-1), the intra- and inter-day relative standard deviations (RSDs) are less than 4.6% and 5.7%, respectively. The recoveries of E2 from environmental water samples are in the range from 88.3% to 99.1% with the RSDs less than 7.2%.

A core-shell surface magnetic molecularly imprinted polymers with fluorescence for λ-cyhalothrin selective recognition

In this study, we report here a general protocol for making core-shell magnetic Fe3O4/SiO2-MPS/MIPs (MPS = 3-(methacryloxyl) propyl trimethoxysilane, MIPs = molecularly imprinted polymers, Fe3O4/SiO2-MPS as core, MIPs as shell) via a surface molecular imprinting technique for optical detection of trace λ-cyhalothrin. The fluorescent molecularly imprinted polymer shell was first prepared by copolymerization of acrylamide with a small quantity of allyl fluorescein in the presence of λ-cyhalothrin to form recognition sites without doping. The magnetic Fe3O4/SiO2-MPS/MIPs exhibited paramagnetism, high fluorescence intensity, and highly selective recognition. Using fluorescence quenching as a detecting tool, Fe3O4/SiO2-MPS/MIPs were successfully applied to selectively and sensitively detect λ-cyhalothrin, and a linear relationship could be obtained covering a wide concentration range of 0-50 nM with a correlation coefficient of 0.9962 described by the Stern-Volmer equation. The experimental results of practical detection revealed that magnetic Fe3O4/SiO2-MPS/MIPs as an attractive recognition element was satisfactory for determination of trace λ-cyhalothrin in honey samples. This study, therefore, demonstrated the potential of MIPs for detection of λ-cyhalothrin in food.

Hg2+ion-imprinted polymers sorbents based on dithizone–Hg2+chelation for mercury speciation analysis in environmental and biological samples

Novel Hg²⁺ion-imprinted polymers were synthesized using the chelate of dithizone and Hg²⁺as template for mercury speciation analysis.