Molecularly Imprinted Heterostructure-Assisted Laser Desorption Ionization Mass Spectrometry Analysis and Imaging of Quinolones.

Quinolone residues resulting from body metabolism and waste discharge pose a significant threat to the ecological environment and to human health. Therefore, it is essential to monitor quinolone residues in the environment. Herein, an efficient and sensitive matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) method was devised by using a novel molecularly imprinted heterojunction (MIP-TNs@GCNs) as the matrix. Molecularly imprinted titanium dioxide nanosheets (MIP-TNs) and graphene-like carbon nitrides (GCNs) were associated at the heterojunction interface, allowing for the specific, rapid, and high-throughput ionization of quinolones. The mechanism of MIP-TNs@GCNs was clarified using their adsorption properties and laser desorption/ionization capability. The prepared oxygen-vacancy-rich MIP-TNs@GCNs heterojunction exhibited higher light absorption and ionization efficiencies than TNs and GCNs. The good linearity (in the quinolone concentration range of 0.5-50 pg/µL, R2 > 0.99), low limit of detection (0.1 pg/µL), good reproducibility (n = 8, relative standard deviation [RSD] < 15%), and high salt and protein resistance for quinolones in groundwater samples were achieved using the established MIP-TNs@GCNs-MALDI/MS method. Moreover, the spatial distributions of endogenous compounds (e.g., amino acids, organic acids, and flavonoids) and xenobiotic quinolones from Rhizoma Phragmitis and Rhizoma Nelumbinis were visualized using the MIP-TNs@GCNs film as the MALDI/MS imaging matrix. Because of its superior advantages, the MIP-TNs@GCNs-MALDI/MS method is promising for the analysis and imaging of quinolones and small molecules.

A review: Development and application of surface molecularly imprinted polymers toward amino acids, peptides, and proteins.

Molecularly imprinted polymers (MIPs) have received wide interests in the bioanalysis field as "artificial antibodies". They can mimic biological receptors by selectively recognizing and adsorbing target molecules owing to their specific affinity to the targets. Traditional MIPs obtained by bulk imprinting have some defects, including low adsorption capacity, poor site accessibility, restricted mass transfer, and irregular morphology, which limit their development. Surface molecularly imprinted polymers (SMIPs) show the features of large surface area, allow fast mass transfer, and have high adsorption capacity and efficiency. They have been intensively used in the research of amino acids, peptides, and proteins due to these advantages. In this review, we systematically summarize the preparation of SMIPs including components and polymerization strategies, and their applications focusing on amino acids, peptides, and proteins are discussed in detail. Finally, future trends and challenges for the design and development of SMIPs are described.

Metabolic networks of plasma and joint fluid base on differential correlation.

Whether osteoarthritis (OA) is a systemic metabolic disorder remains controversial. The aim of this study was to investigate the metabolic characteristics between plasma and knee joint fluid (JF) of patients with advanced OA using a differential correlation metabolic (DCM) networks approach. Plasma and JF were collected during the joint replacement surgery of patients with knee OA. The biological samples were pretreated with standard procedures for metabolite analysis. The metabolic profiling was conducted by means of liquid mass spectrometry coupled with a AbsoluteIDQ kit. A DCM network approach was adopted for analyzing the metabolomics data between the plasma and JF. The variation in the correlation of the pairwise metabolites was quantified across the plasma and JF samples, and networks analysis was used to characterize the difference in the correlations of the metabolites from the two sample types. Core metabolites that played an important role in the DCM networks were identified via topological analysis. One hundred advanced OA patients (50 men and 50 women) were included in this study, with an average age of 65.0 ± 7.6 years (65.6 ± 7.1 years for females and 64.4 ± 8.1 years for males) and a mean BMI of 32.6 ± 5.8 kg/m2 (33.4 ± 6.3 kg/m2 for females and 31.7 ± 5.3 kg/m2 for males). Age and BMI matched between the male and female groups. One hundred and forty-five nodes, 567 edges, and 131 nodes, 407 edges were found in the DCM networks (p < 0.05) of the female and male groups, respectively. Six metabolites in the female group and 5 metabolites in the male group were identified as key nodes in the network. There was a significant difference in the differential correlation metabolism networks of plasma and JF that may be related to local joint metabolism. Focusing on these key metabolites may help uncover the pathogenesis of knee OA. In addition, the differential metabolic correlation between plasma and JF mostly overlapped, indicating that these common correlations of pairwise metabolites may be a reflection of systemic characteristics of JF and that most significant correlation variations were just a result of "housekeeping" biological reactions.

Selective recognition and enrichment of sterigmatocystin in wheat by thermo-responsive imprinted polymer based on magnetic halloysite nanotubes.

Two thermo-responsive molecularly imprinted polymers (MHNTs@MIP and MCNTs@MIP) for the selective extraction of sterigmatocystin have been prepared on the surface of the magnetic halloysite nanotubes (MHNTs) and magnetic carbon nanotubes (MCNTs), respectively. 1, 8-dihydroxyanthraquinone, n-isopropyl acrylamide, methacrylic acid, ethylene dimethacrylate and dimethyl sulfoxide were used as the dummy template, thermo-sensitive functional monomer, co-monomer, cross-linker and porogen, respectively. The magnetic properties, adsorption properties as well as the temperature responsive behaviors of MHNTs@MIP and MCNTs@MIP were systematically studied and compared for the first time. Enough saturation magnetizations of MHNTs@MIP (9.42 emu/g) and MCNTs@MIP (10.54 emu/g) were obtained. MHNTs@MIP and MCNTs@MIP also showed controllable adsorption and release behaviors to sterigmatocystin in response to the temperature change (35 °C and 20 °C). Compared with MCNTs@MIP, MHNTs@MIP had higher adsorption affinity (KL = 0.120 L/mg), higher adsorption kinetic (K2 = 0.0100 g/(mg•min)) and higher imprinting factor (5.22) to sterigmatocystin. These results indicated that MHNTs@MIP was favorable adsorbent for the selective separation of sterigmatocystin. Furthermore, the elution conditions of MHNTs@MIP were optimized by response surface methodology. Under the optimal conditions, MHNTs@MIP coupled with high performance liquid chromatography were successfully applied to the selective recognition, purification, enrichment and detection of sterigmatocystin in wheat samples. The recoveries were calculated from 88.62% to 102.9% with RSDs less than 3.5 % and limit of detection of 1.1 µg/kg. This work provided a suitable carrier for the preparation of imprinted polymers and a practical approach for highly selective recognition and determination of analytes in real samples.

Selective recognition and enrichment of carbamazepine in biological samples by magnetic imprinted polymer based on reversible addition-fragmentation chain transfer polymerization.

A well-defined molecularly imprinted polymer (Fe3O4@CS@MIP) was synthesized via reversible addition-fragmentation chain transfer polymerization for magnetic solid-phase extraction coupled with high-performance liquid chromatography-diode array detector to detect carbamazepine (CBZ) in biological samples. The composition of Fe3O4@CS@MIP was selected by a two-step screening method. 4-vinyl pyridine, divinylbenzene and dimethylformamide were chosen as the functional monomer, cross-linker and porogen, respectively. The imprinted layer was coated on the surface of the chain transfer agent-modified magnetic chitosan nanoparticles. The prepared Fe3O4@CS@MIP was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurement and vibrating sample magnetometer. The results indicated that Fe3O4@CS@MIP had a large surface area (265.8 m2/g), high saturation magnetization (19.88 emu/g) and uniform structure. Besides, the binding property of the Fe3O4@CS@MIP was studied in detail. The Fe3O4@CS@MIP showed high imprinting factor (IF = 4.83) and desirable adsorption capacity (323.10 µmol/g) to CBZ. Under the optimum conditions, the developed method exhibited excellent linearity (R2>0.999) in the range of 0.01-0.5 mg/L and 1.0-30.0 mg/L, and the limits of detection were 1.0 µg/L and 9.6 µg/L for the urine and serum samples, respectively. Good recoveries (88.22%-101.18%) were obtained with relative standard deviations less than 4.83%. This work provided a practical approach for the selective extraction and detection of CBZ in real samples.

Novel mixed hemimicelles based on nonionic surfactant-imidazolium ionic liquid and magnetic halloysite nanotubes as efficient approach for analytical determination.

The co-adsorption of mixed nonionic surfactant and imidazolium-based ionic liquid, Triton X100 (TX100), with 1-cetyl-3-methylimidazolium bromide (C16mimBr) adsorbed onto the surface of magnetic halloysite nanotubes (MHNTs) was used as an efficient adsorbent for simultaneous determination of amlodipine and nimodipine in urine. The designed adsorbent was characterized by TEM, TGA, FTIR, and DLS analysis methods. All the parameters that influence the extraction efficiency are optimized with the aid of response surface methodology (RSM). The effects of nonionic surfactant TX100 with different structures of ionic-liquid-coated MHNTs were investigated. Under optimum conditions, extraction recoveries of amlodipine and nimodipine were in the range of 73.8-81.2 and 94.3-96.1%, with RSDs (n = 3) of 2.6-5.5% in spiked urine samples, respectively. The adsorption mechanism principal of mixed hemimicelles was discussed in this study. The limit of detection obtained for analytes was < 0.002 µg·mL-1. To our knowledge, this was the first attempt using a mixed hemimicelle solid-phase extraction (SPE) based on MHNTs and nonionic surfactant and imidazolium-based ionic liquid for the simultaneous determination of amlodipine and nimodipine in biological samples. Graphical abstract ᅟ.

Colorimetric chiral recognition of D/L-phenylalanine based on triangular silver nanoplates.

A new colorimetric analysis approach for chiral recognition of D- and L-forms of phenylalanine (phe) was developed based on triangular silver nanoplates (TAg-NPs). The TAg-NPs could be used as chiral colorimetric probes for D- and L-forms of phe. Upon addition of D-phe to TAg-NPs solution, a color change from blue to purple to pink could be observed, while no obvious color change was found on addition of L-phe. L-phe could prevent the TAg-NPs from being etched to small size particles while the protective effect of D-phe was weak. Moreover, the enantiomeric excess of D-phe could be determined using the proposed chiral assay in the percentage of L-phe from 0 to 100% with a correlation coefficient of 0.9855. The phenomenon could be monitored by bare eyes and quantified analysis by UV-Vis spectrophotometry. The developed approach had several advantages, such as simplicity, visualization, short analysis time and low cost. This study presented a fast visualization analysis method of chiral D/L-phenylalanine and may lay the foundation for the development of visualization chiral recognition of other target analytes.

Colorimetric sensor for cimetidine detection in human urine based on d-xylose protected gold nanoparticles.

Herein, a simple, novel, and rapid colorimetric sensor for cimetidine (Cim) detection based on d-xylose protected gold nanoparticles (d-x@AuNPs) has been developed for the first time. The d-x@AuNPs were characterized by UV-vis, TEM and FT-IR techniques. Cimetidine causes the aggregation of d-x@AuNPs due to the formation of a strong covalent Au-N bond and electrostatic binding. As the cimetidine concentration increased, the color of the solutions gradually changed from wine-red to blue, and the large absorption band shifted from 533 to 680 nm upon d-x@AuNP aggregation. The effects of different experimental parameters were investigated. A comparative study on the detection of Cim using citrated capped AuNPs and d-x@AuNPs was presented. Under optimum conditions, the UV-vis spectra showed that the absorption ratio (A680/A533) increased linearly with the concentration of cimetidine in the range of 7 × 10-8 to 3 × 10-6 M with a correlation coefficient of 0.9956 and a limit of detection of 1 × 10-8 M without needing any complicated instruments. The selectivity of the d-x@AuNP detection system for cimetidine was excellent when compared with other ions and analytes. Due to their rapid and visible color changes, and their remarkable selectivity, the d-x@AuNPs synthesized in this study were suitable and could be applied to the detection of cimetidine in human urine.

Solid phase extraction based on porous magnetic graphene oxide/ß-cyclodextrine composite coupled with high performance liquid chromatography for determination of antiepileptic drugs in plasma samples.

In this study, a novel solid phase extraction based on porous magnetic graphene oxide-cyclodextrin polymers (MGO-CD) was developed with aromatic linker and used for the simultaneous extraction and preconcentration of trace antiepileptic drugs in plasma. The characteristics of MGO-CD were assessed by Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface areas (BET), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Magnetic cyclodextrin polymeric material exhibited a high specific surface area (187m2g-1), large pore volume (0.12cm3g-1), good saturated magnetization (37.68emug-1), and excellent dispersibility in aqueous solution. Various parameters influencing the extraction recovery of drugs were studied. The method exhibited good linearity in the range of 1-50µgmL-1, and the limit of quantitation of carbamazepine, phenytoin, diazepam was 11.89, 47.10 and 16.17ngmL-1, respectively. The recoveries of three antiepileptic drugs range from 78.49 to 100.93% with relative standard deviations less than 5.5%. These analytical results demonstrated that the proposed approach based on MGO-CD was applicable for analysis of antiepileptic drugs in plasma samples.

Determination of quinolones in wastewater by porous ß-cyclodextrin polymer based solid-phase extraction coupled with HPLC.

In this research, a novel insoluble sorbent based on cyclodextrin and rigid aromatic groups tetrafluoroacetonitrile was designed for dispersive insoluble solid-phase extraction (DSPE). Due to its high adsorption capacity, this obtained polymer was applied to separation and concentration of trace quinolones in wastewater before HPLC determination. Various parameters influencing the extraction performance were studied and optimized. A DSPE approach coupled with high performance liquid chromatography was developed for the determination of four quinolones in wastewater samples. The limit of quantitation of fleroxacin, ciprofloxacin, gatifloxacin, norfloxacin were 2.67, 3.17, 4.75, 5.50ngmL-1, respectively. The recoveries of four quinolones range from 96.43 to 103.3% with relative standard deviations less than 4.5%. These results demonstrated that the proposed approach based on CDP was efficient, low-cost for extraction of quinolones from wastewater.