Magnetic boronate modified molecularly imprinted polymers on magnetite microspheres modified with porous TiO2 (Fe3O4@pTiO2@MIP) with enhanced adsorption capacity for glycoproteins and with wide operational pH range.

Boronate-affinity based molecularly imprinted polymers (MIPs) are beset by the unsatisfied adsorption capacity and narrow working pH ranges. A magnetic molecularly imprinted polymer containing phenylboronic acid groups was placed on the surface of Fe3O4 (magnetite) microspheres coated with porous TiO2 (Fe3O4@pTiO2@MIP). In contrast to its silica analog (Fe3O4@SiO2@MIP), the flowerlike Fe3O4@pTiO2 offers more binding sites for templates. Thus, the adsorption capacity of the Fe3O4@pTiO2@MIP is strongly enhanced. The strong electron-withdrawing effects of Ti(IV) enable the boronic acid of the MIP to have better affinity for glycoproteins at a wide pH range from 6.0 to 9.0. Consequently, the Fe3O4@pTiO2@MIP exhibits higher adsorption for glycoproteins than Fe3O4@SiO2@MIP in both basic and acidic medium. The Fe3O4@pTiO2@MIPs were eluted with 5% acetic acid aqueous solution containing 30% acetonitrile, and the eluate was analyzed by MALDI-TOF MS. The method was applied to the selective extraction and quantitation of horseradish peroxidase (HRP) in spiked fetal bovine serum (FBS). The linear range is 0.40-10 µg·mL-1 with the limit of detection of 0.31 µg·mL-1. In our perception, this work has a wide scope in that is paves the way to a more widespread application of boronate affinity based MIPs for analysis of glycoproteins and related glyco compounds even at moderately acidic pH values. Graphical abstract Schematic presentation of the magnetic boronate modified molecularly imprinted polymer on magnetic spheres modified with porous TiO2 (Fe3O4@pTiO2@MIP). It was applied to extract glycoprotein in spiked both basic fetal bovine serum (FBS) and acidic urine samples prior to quantitation by MALDI-TOF mass spectrometry.

A salicylaldehyde benzoyl hydrazone based near-infrared probe for copper(ii) and its bioimaging applications.

Developing highly sensitive and selective methods for Cu2+ detection in living systems is of great significance in clinical copper-related disease diagnosis. In this work, a near infrared (NIR) fluorescent probe, CySBH, with a salicylaldehyde benzoyl hydrazone group as a selective and sensitive receptor for Cu2+ was designed and synthesized. The specific coordination of the salicylaldehyde benzoyl hydrazone group in CySBH with Cu2+ can induce a distinct quench of the fluorescence intensity, allowing for real-time tracking of Cu2+. We have demonstrated that CySBH could rapidly recognize Cu2+ with good selectivity and high sensitivity. Moreover, on the basis of low cell cytotoxicity, the probe was used to visualize Cu2+ in two cell lines by fluorescence imaging. Furthermore, CySBH can also be used to monitor Cu2+ in vivo due to its NIR emission properties. These overall results illustrate that the NIR fluorescent probe CySBH provides a novel approach for the selective and sensitive monitoring of Cu2+ in living systems.

A colorimetric method for screening α-glucosidase inhibitors from flavonoids using 3,3',5,5'-tetramethylbenzidine as a chromogenic probe.

A facile and novel colorimetric method for screening of α-glucosidase inhibitors (AGIs) from flavonoids using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic probe is proposed. This method is based on the colorimetric detection of ascorbic acid (AA) through the TMB oxidation reaction catalyzed by horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2). In the TMB/H2O2/HRP system, HRP catalyzes the oxidation of H2O2 to ‧OH radical which oxidizes TMB to blue-colored oxidized TMB (oxTMB). In the presence of AA, the production of ‧OH radical is suppressed and causes the decrease of oxTMB, resulting in the fading of the blue color and the decrease of absorbance at 652 nm. Based on this, the existence of AA can be facilely identified. In the 2-O-α-d-glucopyranosyl-l-ascorbic acid (AA-2 G)/α-glucosidase (α-Glu) system, the produced AA inhibits the oxidation of TMB to blue-colored oxTMB. In the presence of AGIs, the production of AA is inhibited, which inhibits the reduction of oxTMB, resulting in a blue color recovery and an increase of the absorbance at 652 nm. Based on this, the colorimetric method is developed for screening of AGIs from 7 flavonoids.

An immobilization enzyme for screening lipase inhibitors from Tibetan medicines.

With the increasing demand for lipase inhibitors and new drugs used in the clinical treatment of obesity, it is of great significance to screen lipase inhibitors from traditional Chinese medicines (TCMs) via capillary electrophoresis. In this work, Fe3O4@TiO2 nanoparticles was fabricated by solvothermal method and employed as an improved magnetic support to immobilize lipase through electrostatic interaction. By the method of transmission electron microscopy, fourier transform infrared spectroscopy and X-ray diffraction, the magnetic nanoparticles were characterized. The immobilized enzyme possessed advantages of a wider range for pH and temperature endurance, better storage stability and reusability. The kinetics performances of the immobilized lipase were studied. When p-Nitrophenyl palmitate (pNPP) was used as enzyme substrate, the Michaelis-Menten constant was calculated to be 2.51 mM and its inhibition constant for Orlistat was ascertained to be 13.41 µM. Ultimately, the established method was applied to lipase inhibitors screening from 6 Tibetan medicines with lipase inhibitory activity and Oxytropis falcate Bunge was screened out for its supreme lipase inhibitory activity. 11 compounds in the Oxytropis falcate Bunge were further screened, five compounds exhibited similar inhibitory activity to Orlistat, and one compound (kaempferol) presented better inhibitory activity than Orlistat, which is the most commonly used drugs to treat obesity in clinic. This work not only developed a method for new anti-obesity drugs discovery, but also provided inspiration for exploring new medicinal value of the TCMs.

"Recent advances on support materials for lipase immobilization and applicability as biocatalysts in inhibitors screening methods"-A review.

With a substantial demand for new anti-obesity drugs for the treatment of obesity, screening lipase inhibitors from natural products has become a popular approach toward drug discovery. Due to the significant advantages of excellent reusability, stability and endurance in extreme pH and temperature conditions, lipase immobilization has been employed as a promising strategy to screen lipase inhibitors. Support is a key factor in the process of enzyme immobilization used to provide excellent biocompatibility, stable physical and chemical properties and abundant binding sites for enzymes. Thus, various supports, including nanofibers, polymeric monoliths, mesoporous materials, nanomaterials, membrane and cellulose paper, are systematically introduced and discussed in this review. Considering these supports, the application of the immobilization of lipase in screening compounds from natural products is also comprehensively reviewed, and the outlook for future research directions is described.

A fluorescent molecularly imprinted device for the on-line analysis of AFP in human serum.

MIT is a promising strategy in antibody free analysis for tumour markers. Conventional nanosized MIPs with off-line analysis are beset by tedious operation and unsatisfactory analysis performance. In this work, an on-line analytical device to directly detect AFP, which is a typical tumour marker in cancer screening, was prepared for the first time. A microscope slide was chosen to be the basis of the device. APBA-PA, a polymerizable fluorescent boronic acid monomer, was synthesised and grafted on the surface of the microscope slide to act as the signal transduction pathway between the templates and the device. Along with the hydrolysis of TEOS and the elution of the templates, a portable, stable, easy to operate and low-cost analysis device for AFP with excellent repeatability was successfully prepared. Owing to the excellent selectivity and highly sensitive fluorescence response ability of the device towards the templates, the on-line detection of AFP in human serum was realized. A series of characterizations were applied to the device, and its analysis performance and possible detection mechanism were carefully studied. Furthermore, the device exhibited appropriate application prospects by comparing its analysis results with those of the commercially available ELISA. In our perception, this work is an important step towards MIPs for clinical applications.

Synthesis of magnetic molecularly imprinted nanoparticles with multiple recognition sites for the simultaneous and selective capture of two glycoproteins.

Many diseases ordinarily have several kinds of biomarkers (most of them belong to the glycoprotein family). Simultaneous capturing of multiple target glycoprotein biomarkers can obtain better specificity compared with single marker detection in early screening of many diseases. In this work, we attempted to prepare magnetic molecularly imprinted nanoparticles with multiple recognition sites. Horseradish peroxidase and ovalbumin as the frequently used glycoproteins for simulation of glycoprotein biomarkers were employed as dual-templates. The simultaneous preorganization of two templates was achieved by introducing 4-formylphenylboronic acid as a functional monomer. To gain a high adsorption capacity for the two templates, the mass ratio of the two templates was precisely investigated. Controllable polymerization of dopamine was applied to synthesize thin imprinted layers that reduce mass transfer resistance and improve the eluted efficiency of the two templates. The resultant magnetic molecularly imprinted nanoparticles exhibited high adsorption capacities of 34.09 and 51.18 mg g-1, respectively. The simultaneous recognition of two templates in spiked fetal bovine serum was also achieved with satisfactory selectivity. The results indicate that this proposed strategy is potentially applicable for simultaneously and selectively capturing several glycoprotein biomarkers used in detecting many diseases.

Improved surface imprinting based on a simplified mass-transfer process for the selective extraction of IgG.

We wished to improve the unsatisfactory adsorption and elution efficiencies in conventional magnetic molecular imprinting technology. In this work, a reliable strategy to prepare magnetic molecularly imprinted nanoparticles (MMINs) with rapid rebinding and elution speed was introduced. To decrease the mass-transfer retention of the templates, glycoprotein immunoglobulin (Ig)G was pre-immobilized to form homogeneous and monostratified three-dimensionally imprinted cavities on the surface of magnetic carriers. To shorten the transfer route of the templates, the polymerizaiton process was controlled precisely to form well-defined molecularly imprinted polymer (MIP) films of thickness 12 nm. In this way, the effectiveness of the mass transfer of the templates was maximized, and the length of the transfer route was minimized. As a result, the prepared MMINs showed improved adsorption and elution efficiencies compared with the conventional magnetic molecularly imprinted polymers (MMIPs), and exhibited great selectivity towards the templates.

Highly dispersed magnetic molecularly imprinted nanoparticles with well-defined thin film for the selective extraction of glycoprotein.

Antibody-free analysis is a potential method for glycoprotein analysis, but the development of this method has been limited by its unfavorable selectivity in recent years. Magnetic molecular imprinting, which integrates the fast separation of magnetic materials with high selectivity towards templates in molecular imprinting, was expected to be an effective sample pretreatment in antibody-free analysis for glycoproteins. However, the aggregation of magnetic imprinted nanoparticles and thick molecularly imprinted polymer (MIP) shells on the surface of magnetic carriers caused an unfavorable adsorption capacity, and unsatisfactory rebinding and elution rates, and has limited its application in glycoprotein extraction. Thus, highly dispersed magnetic molecularly imprinted nanoparticles (MMINs) with a well-defined thin film for the selective extraction of glycoprotein HRP were developed in this work. A solvothermal method was used in this work to improve the dispersity of Fe3O4 NPs (nanoparticles) and the MMINs. The thickness of the MIP film was optimized to provide the optimum extraction efficiency. Thus the adsorption capacity of the MMINs, the rebinding rate and the elution rate of the templates were greatly improved. As a result, the prepared MMINs not only exhibited excellent selectivity and high adsorption capacity to HRP, and an outstanding tolerance for interference, but also showed excellent rebinding and elution rates for extraction application. Furthermore, this method provided a reliable way to improve conventional magnetic molecular imprinting, and showed great potential for the analysis of glycoprotein tumor biomarkers in clinics in the future.

Magnetic molecularly imprinted polymer for the selective extraction of quercetagetin from Calendula officinalis extract.

A new magnetic molecularly imprinted polymers (MMIPs) for quercetagetin was prepared by surface molecular imprinting method using super paramagnetic core-shell nanoparticle as the supporter. Acrylamide as the functional monomer, ethyleneglycol dimethacrylate as the crosslinker and acetonitrile as the porogen were applied in the preparation process. Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM) were applied to characterize the MMIPs, and High performance liquid chromatography (HPLC) was utilized to analyze the target analytes. The selectivity of quercetagetin MMIPs was evaluated according to their recognition to template and its analogues. Excellent binding for quercetagetin was observed in MMIPs adsorption experiment, and the adsorption isotherm models analysis showed that the homogeneous binding sites were distributed on the surface of the MMIPs. The MMIPs were employed as adsorbents in solid phase extraction for the determination of quercetagetin in Calendula officinalis extracts. Furthermore, this method is fast, simple and could fulfill the determination and extraction of quercetagetin from herbal extract.