Surong Mei

Magnetic molecularly imprinted nanoparticles for recognition of lysozyme

Molecular imprinting is an attractive technique for preparing mimics of natural, biological receptors. Nevertheless, the imprinting of macromolecule remains a challenge due to their bulkiness and sensitivity to denaturation. In this work, we presented a method for preparing multifunctional lysozyme-imprinted nanoparticles (magnetic susceptibility, molecular recognition and environmental response). The magnetic susceptibility was imparted through the successful encapsulation of Fe3O4 nanoparticles. Selective lysozyme recognition depended on molecularly imprinted film. Moreover, it was also a hydrophilic stimuli-responsive polymer, which could undergo a reversible change of imprinted cavity in response to a small change in the environmental conditions. Thus, magnetic molecularly imprinted nanoparticles had high adsorption capacity (0.11 mg mg(-1)), controlled selectivity and direct magnetic separation (22.1 emicro g(-1)) in crude samples. After preconcentration and purification with magnetic MIPs nanoparticles, a sensitive chemiluminescence method was developed for determination of lysozyme in human serum samples. The results indicated that the spiked recoveries were changed from 92.5 to 113.7%, and the RSD was lower than 11.8%.

Preparation of mixed-templates molecularly imprinted polymers and investigation of the recognition ability for tetracycline antibiotics

We developed in the present study a set of molecularly imprinted polymers (MIPs) by precipitation polymerization, using four members of tetracycline antibiotics (TCs) as templates (Oxytetracycline, Tetracycline, Chlortetracycline and Doxycycline). Then, based on the imprinting effect of different MIPs (TCs), Oxytetracycline and Chlortetracycline were chosen as mixed-templates to synthesize high selective MIPs for recognition of a family of analytes. And the characterization of obtained MIPs was analyzed by FESEM analysis, Brunauer-Emmett-Teller (BET) method, polymer size analysis, and determination of swelling ratio and COOH capacity. It was shown that the optimal imprinting factors of TCs on mixed-templates MIPs were more than 6.0 and the maximum binding amount of TCs were about 27 micromol g(-1) (Oxytetracycline), 35 micromol g(-1) (Tetracycline), 35 micromol g(-1) (Chlortetracycline) and 39 micromol g(-1) (Doxycycline), respectively. Finally, the mixed-templates MIPs were shown to be promising for on-line solid-phase extraction-HPLC-UV determination of trace TCs in foodstuffs. With a sample loading volume of 10 mL, the enhancement factors were in the range of 159-410.

Highly selective and sensitive determination of dopamine by the novel molecularly imprinted poly(nicotinamide)/CuO nanoparticles modified electrode.

A novel electrochemical sensor was proposed for the determination of dopamine (DA) based on the molecularly imprinted electropolymers (MIPs)/copper oxide (CuO) nanoparticles modified electrode. MIPs were firstly prepared by using nicotinamide as an environment-friendly monomer to selectively recognize the template molecules. CuO nanoparticles were used to enhance the number of imprinted sites per unit surface area of the electrode and then improve the selectivity and sensitivity of the electrochemical sensor. Thus, the obtained electrochemical sensor could effectively minimize the interferences caused by ascorbic acid (AA), uric acid (UA) and sample matrix. The linear range for the detection of DA was changed from 0.02 μmol L(-1) to 25 μmol L(-1) with the detection limit of 8 nmol L(-1) (S/N=3), which was lower than those of the reported MIPs-based sensor. Finally, the proposed method was applied to measure dopamine in serum samples. The spiked recoveries were changed from 96.9% to 105.9% and the RSD was not higher than 8.8%. It was shown that the proposed sensor exhibited significant promise as a reliable technique for the detection of DA in human serum samples.

Rapid and selective extraction of multiple macrolide antibiotics in foodstuff samples based on magnetic molecularly imprinted polymers

Magnetic molecularly imprinted polymers (MMIPs) were prepared based on surface molecular imprinting using erythromycin (ERY) as template molecule and Fe3O4 nanoparticles as support substrate. The MMIPs possessed high adsorption capacity of 94.1 mg/g for ERY and the imprinting factor was 11.9 indicating good imprinted effect for ERY. Selective evaluation demonstrated favorable selectivity of MMIPs for multiple macrolide antibiotics (MACs). Using MMIPs as adsorptive material, a rapid and convenient magnetic solid-phase extraction (MSPE) procedure was established for simultaneous and selective separation of six MACs in pork, fish and shrimp samples, then the MACs was subjected to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. At different fortified concentrations, the extraction recoveries could reach 89.1% and the relative standard deviations were lower than 12.4%. Chromatogram revealed the response signals of MACs in spiked samples were greatly enhanced and matrix interferences were effectively eliminated after treatment with MSPE. The proposed MSPE procedure coupled with HPLC-UV realized selective and sensitive determination of multiple MACs in foodstuff samples.

Rapid and selective determination of urinary lysozyme based on magnetic molecularly imprinted polymers extraction followed by chemiluminescence detection.

A rapid, low cost and selective chemiluminescence method coupled with magnetic molecularly imprinted polymers extraction was developed to detect lysozyme in human urine samples. Compared with traditional solid-phase extraction, this method could achieve selective extraction for the lysozyme, avoid the time consuming elution from a column or centrifugation steps, and then showed great potential in the high-throughput screening of clinical samples. The parameters affecting the performance of extraction and chemiluminescence were investigated. Under optimal conditions, the whole analytical procedure was completed within 12 min and spiked recovery ranged from 90.1% to 103.7% (R.S.D.≤6.7%). The limit of quantitation was 5 ng mL(-1). Furthermore, the results obtained by the proposed method were linearly correlated to those by commercial lysozyme detection kit (r=0.9595). Finally, the validated method was used to measure the urinary lysozyme of renal disease patients and healthy controls. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.

Determination of trace 2,4-dinitrophenol in surface water samples based on hydrophilic molecularly imprinted polymers/nickel fiber electrode.

A rapid, sensitive and selective electrochemical method was proposed for the determination of 2,4-dinitrophenol (2,4-DNP) in surface water samples, using hydrophilic molecular imprinted polymers (MIPs) as the recognition element and nickel (Ni) fiber as the catalytic element. Hydrophilic MIPs were synthesized using 2,4-DNP as the template, acrylamide as the monomer, glycidilmethacrylate as the pro-hydrophilic co-monomer and acetonitrile as the solvent. Hydrophilic modification could enhance the accessibility of 2,4-DNP to the imprinted cavities and improve the selective recognition properties of traditional MIPs in water medium. Subsequently, hydrophilic MIPs/Ni fiber electrode was prepared to determine trace 2,4-DNP by cyclic voltammetry. The parameters affecting the analytical performance were investigated. Under optimized conditions, the linear range was 0.7-30 μg L⁻¹ and the detection limit was 0.1 μg L⁻¹. Finally, the proposed method was applied to measure 2,4-DNP in surface water samples. The spiked recoveries were changed from 91.3% to 102.6% and the RSD was not higher than 5.1%. There was no statistically significant difference between the results obtained by the proposed method and the traditional chromatographic method.

A simple and sensitive immunoassay for the determination of human chorionic gonadotropin by graphene-based chemiluminescence resonance energy transfer

In this study, we report a strategy of chemiluminescence resonance energy transfer (CRET) using graphene as an efficient long-range energy acceptor. Magnetic nanoparticles were also used in CRET for simple magnetic separation and immobilization of horseradish peroxidase (HRP)-labeled anti-HCG antibody. In the design of CRET system, the sandwich-type immunocomplex was formed between human chorionic gonadotropin (HCG, antigen) and two different antibodies bridged the magnetic nanoparticles and graphene (acceptors), which led to the occurrence of CRET from chemiluminescence light source to graphene. After optimizing the experimental conditions, the quenching of chemiluminescence signal depended linearly on the concentration of HCG in the range of 0.1 mIU mL(-1)-10 mIU mL(-1) and the detection limit was 0.06 mIU mL(-1). The proposed method was successfully applied for the determination of HCG levels in saliva and serum samples, and the results were in good agreement with the plate ELISA with colorimetric detection. It could also be developed for detection of other antigen-antibody immune complexes by using the corresponding antigens and respective antibodies.

Online coupling of molecularly imprinted solid-phase extraction to HPLC for determination of trace tetracycline antibiotic residues in egg samples

An automated system has been developed for the determination of trace tetracycline antibiotics (TCs) in egg samples, based on online molecularly imprinted solid-phase extraction (MISPE) coupling with high-performance liquid chromatography (HPLC). Oxytetracycline and chlortetracycline were chosen as mixed templates to synthesize highly selective molecularly imprinted polymers for online extraction. Under the optimal online MISPE-HPLC condition, 10 mL egg samples were injected into the MISPE column and then the matrix was washed out. By rotating the switching valve, TCs were transferred to the analytical column and then separated by HPLC. Because sample pretreatment and chromatographic separation were carried out simultaneously, the whole analytical time (18 min) was significantly shortened compared with conventional offline techniques. The detection limits ranged from 0.8 to 1.3 ng/g. The enhancement factors were in the range of 159-410. The spiked recoveries of TCs in real egg samples ranged from 91.6 to 107.6% and the relative standard deviations (RSDs) were not higher than 4.0%.

Exposure to organochlorine pesticides and non-Hodgkin lymphoma: a meta-analysis of observational studies

Growing evidence indicates that exposure to organochlorine pesticides (OCPs) could increase non-Hodgkin lymphoma (NHL) risk. However, results from epidemiological studies investigating this association remain controversial. We thus conducted a meta-analysis to quantitatively evaluate the association between OCP exposure and NHL risk. Relevant publications were searched in PubMed, Web of Science, and Embase and identified according to the inclusion criteria. Thirteen studies (6 nested case-control, 1 case-cohort, and 6 case-control) were selected for this meta-analysis. We used odds ratios (ORs) with 95% confidence intervals (CIs) to estimate the relationship between OCPs exposure and NHL risk. The summary OR for included studies was 1.40 (95% CI 1.27 to 1.56). No overall significant heterogeneity in the OR was observed (Ph = 0.253, I2 = 12.6%). Furthermore, OR estimates in subgroup analyses were discussed, and strong associations were observed for dichlorodiphenyldichloroethylene (DDE, OR = 1.38, 95% CI 1.14 to 1.66), hexachlorocyclohexane (HCH, OR = 1.42, 95% CI 1.08 to 1.87), chlordane (OR = 1.93, 95% CI 1.51 to 2.48), and hexachlorobenzene (HCB, OR = 1.54, 95% CI 1.20 to 1.99). This meta-analysis had suggested that total OCPs of interest was significantly positively associated with NHL risk.

Selective Solid-Phase Extraction of Lead Ions in Water Samples Using Three-Dimensional Ion-Imprinted Polymers

Ion-imprinted polymers (IIPs) have drawn much attention in the selective determination of heavy metals. In this study, 8-hydroxyquinoline-grafted gelatin with different types of functional groups was first introduced as a biomolecular monomer to enhance the selectivity of imprinted cavities. Based on its swelling and film-forming properties, a simple strategy containing formation of the hydrogel film, swelling/folding followed by cross-linking, was proposed to prepare three-dimensional IIPs with high adsorption capacity (235.7 mg g(-1)), strong selectivity (imprinted factor was 2.9), and rapid kinetics. Based on the different swelling container, different morphologies of IIPs could be prepared to satisfy the requirements of practical application. Consequently, the IIPs extraction coupled with a spectrophotometric method was applied for determination of lead ions, and the limit of detection was 0.2 ng mL(-1), which could be used for monitoring of Pb(II) in drinking water and surface water.