Yuhai Tang

Combination of surface imprinting and immobilized template techniques for preparation of core–shell molecularly imprinted polymers based on directly amino-modified Fe3O4 nanoparticles for specific recognition of bovine hemoglobin

In this work, the core-shell bovine hemoglobin (BHb)-imprinted superparamagnetic nanoparticles (Fe3O4@BHb-MIPs) were synthesized by combining for the first time a surface imprinting technique and a two-step immobilized template strategy. Initially, amino-functionalized Fe3O4 nanoparticles (Fe3O4@NH2) were synthesized directly through a facile one-pot hydrothermal method. Next, BHb was immobilized on the surface of Fe3O4@NH2 through non-covalent interactions. Then, siloxane co-polymerization on the Fe3O4@NH2-protein complex surface resulted in a polymeric network molded around BHb which then became further immobilized. Finally, a thin polymer layer with specific recognition cavities for BHb was formed on the surface of Fe3O4@NH2 after the removal of the template protein. The morphology and structure property of the prepared magnetic nanoparticles were characterized by transmission electronic microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). To obtain the best selectivity and binding performance, the polymerization and adsorption conditions were investigated in detail. Under the optimized conditions, the Fe3O4@BHb-MIPs exhibited fast adsorption kinetics, large binding capacity, significant selectivity, and favorable reproducibility. The resultant Fe3O4@BHb-MIPs could not only specifically extract BHb from a mixed standard protein mixture, but also selectively enriched BHb from a real bovine blood sample. In addition, the synthetic process was quite simple and the stability and regeneration of the Fe3O4@BHb-MIPs were also satisfactory.

A highly-efficient imprinted magnetic nanoparticle for selective separation and detection of 17β-estradiol in milk.

In this work, we prepared molecularly imprinted polymers (MIPs) combining surface molecular imprinting technique and magnetic separation for separation and determination of 17β-estradiol (E2) from milk. During the synthesis process, the acryloyl chloride was specially used to graft double bonds on Fe3O4 nanoparticles and served as co-functional monomer cooperating with acrylamide. The morphology, structure property, and the best polymerization and adsorption conditions of the prepared magnetic nanoparticles were investigated in detail. The obtained nanomaterials displayed high adsorption capacity of 12.62mg/g, fast equilibrium time of 10min, and satisfactory selectivity for target molecule. Whats more, the MIPs was successfully applied as sorbents to specifically separate and enrich E2 from milk with a relatively high recovery (88.9-92.1%), demonstrating the potential application of the MIPs as solid phase extractant for rapid, highly-efficient, and cost-effective sample analysis.

Potassium permanganate-glyoxal chemiluminescence system for flow injection analysis of cephalosporin antibiotics: cefalexin, cefadroxil, and cefazolin sodium in pharmaceutical preparations

A sensitive flow injection chemiluminescence (FL-CL) method for the determination of cephalosporin antibiotics, was developed. The method was based on that cephalosporin antibiotics could enhance the CL reaction of glyoxal and KMnO(4) in sulfuric acid. Method development included the optimization of reagent concentrations and flow-rate. Under the optimized conditions, three cephalosporin antibiotics: cefalexin, cefadroxil, and cefazolin sodium, were determined. The detection limits of the method are 10ngml(-1) cefalexin, 2ngml(-1) cefadroxil, and 2ngml(-1) cefazolin sodium. The method was successfully applied to the determination of three cephalosporin antibiotics in pharmaceutical preparations.

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%.

Specific recognition of bovine serum albumin using superparamagnetic molecularly imprinted nanomaterials prepared by two-stage core–shell sol–gel polymerization

A novel type of uniform magnetic imprinted nanomaterial for the recognition of bovine serum albumin (BSA) was prepared by anchoring MIP shells on the surface of silica deposited Fe3O4 NPs via a surface imprinting process and two-stage core-shell sol-gel polymerization. The resulting magnetic nanomaterials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and a vibrating sample magnetometer (VSM). The measurements indicated that the as-synthesized nanospheres exhibited good dispersion, high crystallinity, and satisfactory superparamagnetic properties. Moreover, the obtained Fe3O4@BSA-MIPs had a high saturation magnetization (43.82 emu g-1), which allowed them to be easily separated from solution by means of an external magnetic field. The thickness of the imprinted polymer layer was approximately 5 nm, which would be effective for the mass transport between the solution and the surface of Fe3O4@BSA-MIPs. The kinetic adsorption experiment showed that the imprinted nanomaterials could reach equilibrium within 15 min and be well described by the second-order kinetics model, indicating chemical adsorption might be the rate-limiting step. Meanwhile, the imprinting factor and selectivity coefficient of the Fe3O4@BSA-MIPs were as high as 16.4 and 4.65, displaying excellent selectivity towards BSA. In addition, the resulting imprinted polymers were without obvious deterioration after ten adsorption-desorption cycles and different batches of which exhibited excellent reproducibility. Successful application in the selective separation and enrichment of BSA from a bovine blood sample and good recovery after a reasonably mild elution suggested that the Fe3O4@BSA-MIPs could specifically capture BSA from a real complex matrix and had potential value in practical applications.

Specific removal of protein using protein imprinted polydopamine shells on modified amino-functionalized magnetic nanoparticles

Thin imprinted shells over functionalized magnetic nanoparticles is an effective solution to weaken mass transfer resistance, achieve high binding capacity, and attain rapid separation. In this work, a simple, green, and effective approach was developed to imprint bovine serum albumin (BSA) on the surface of amino-modified Fe3O4 nanoparticles (Fe3O4@NH2) using dopamine as monomer through a two-step immobilized template strategy. The results of X-ray diffraction and vibrating sample magnetometry indicated that the as-synthesized nanomaterials exhibited high crystallinity and satisfactory superparamagnetic properties. Transmission electron microscopy and Fourier transform infrared spectroscopy of the products showed that polydopamine shells successfully attached onto Fe3O4@NH2. The polydopamine shells with a thickness of about 10 nm enable the template recognition sites to be accessed easily, and exhibit fast kinetics and high adsorption capacity in aqueous solution. Meanwhile, an excellent selectivity towards BSA has been presented when bovine hemoglobin (BHb), transferrin, and immunoglobulin G (IgG) were employed as competitive proteins. Good recovery after a reasonably mild elution and successful capture of the target protein from a real sample of bovine blood suggests its potential value in practical applications. In addition, the resultant polymers were stable and had no obvious deterioration after six adsorption–regeneration cycles. The versatility of the proposed method has also been verified by choosing four other proteins with different isoelectric points as the templates.

Monolithic cryogels made of agarose–chitosan composite and loaded with agarose beads for purification of immunoglobulin G

In order to obtain a novel absorbent with high adsorption capacity for the purification of immunoglobulin G (IgG), continuous supermacroporous agarose beads embedded agarose-chitosan composite monolithic cryogels (agarose-chitosan cryogels) were prepared by cryo-copolymerization of agarose-chitosan blend solutions with glutaraldehyde as the crosslinker in the presence of agarose beads. After coupling 2-mercaptopyridine onto divinylsulfone-activated matrix, the obtained cryogels were used for the purification of IgG. The microstructure morphologies of the cryogels were analyzed by scanning electron microscopy. The results showed that the obtained cryogels possess interconnected pores of 10-100 μm size. The specific surface area was 350 m(2)/g with maximum adsorption capacity of IgG 71.4 mg/g. The cryogels showed workable stability, and can be reused at least 15 times without significant loss in adsorption capacity. IgG purity after one-step purification from human plasma was monitored by electrophoresis and the average recovery was estimated to be 90%.

Selective extraction and determination of chlorogenic acid in fruit juices using hydrophilic magnetic imprinted nanoparticles

In this paper, the novel hydrophilic magnetic molecularly imprinted nanoparticles were developed for selective separation and determination of chlorogenic acid in aqueous fruit juices. The polymers were prepared by using amino-functionalized magnetic nanoparticles as carriers, branched polyethyleneimine as functional monomer, and chlorogenic acid as template molecule. Branched polyethyleneimine with abundant active amino groups could react with template sufficiently, and its unique dendritic structure may amplify the number of the imprinted cavities. Meanwhile, it would improve the hydrophilicity of imprinted materials for attaining high extraction efficiency. The resulted polymers exhibit fast kinetics, high adsorption capacity, and favorable selectivity. In addition, the obtained nanoparticles were used as solid-phase extraction sorbents for selective isolation and determination of chlorogenic acid in peach, apple, and grape juices (0.92, 4.21, and 0.75 μg mL(-1), respectively).

Distinct reactivity of Morita–Baylis–Hillman acetates as a novel C2 component in amine-catalyzed [2 + 2 + 2] and [2 + 4] annulations

Amine-catalyzed [2 + 2 + 2] and [2 + 4] annulations of Morita-Baylis-Hillman (MBH) acetates with cyano activated alkenes and 1,3-azadienes have been developed to provide cyclohexanes and tetrahydropyridines. In the annulations, MBH acetates serve as a novel C(2) component with an inactive homoallylic methyl involved in the bond formation.

Novel polydopamine imprinting layers coated magnetic carbon nanotubes for specific separation of lysozyme from egg white

Novel core-shell nanocomposites, consisting of magnetic carbon nanotubes (MCNTs) core surrounded by a thin polydopamine (PDA) imprinting shell for specific recognition of lysozyme (Lyz), were fabricated for the first time. The obtained products were characterized and the results showed that the PDA layer was successfully attached onto the surface of MCNTs and the corresponding thickness of imprinting layer was just about 10nm which could enable the template access the recognition cavities easily. The polymerization conditions and adsorption performance of the resultant nanomaterials were investigated in detail. The results indicated that the obtained imprinted polymers showed fast kinetic and high affinity towards Lyz and could be used to specifically separate Lyz from real egg white. In addition, the prepared materials had excellent stability and no obvious deterioration after five adsorption-regeneration cycles. Easy preparation, rapid separation, high binding capacity, and satisfactory selectivity for the template protein make this polymer attractive in biotechnology and biosensors.