Pengfei Du

A Competitive Bio-Barcode Amplification Immunoassay for Small Molecules Based on Nanoparticles

A novel detection method of small molecules, competitive bio-barcode amplification immunoassay, was developed and described in this report. Through the gold nanoparticles (AuNPs) probe and magnetic nanoparticles (MNPs) probe we prepared, only one monoclonal antibody can be used to detect small molecules. The competitive bio-barcode amplification immunoassay overcomes the obstacle that the bio-barcode assay cannot be used in small molecular detection, as two antibodies are unable to combine to one small molecule due to its small molecular structure. The small molecular compounds, triazophos, were selected as targets for the competitive bio-barcode amplification immunoassay. The linear range of detection was from 0.04 ng mL−1 to 10 ng mL−1, and the limit of detection (LOD) was 0.02 ng mL−1, which was 10–20 folds lower than ELISA (Enzyme Linked Immunosorbent Assay). A practical application of the proposed immunoassay was evaluated by detecting triazophos in real samples. The recovery rate ranged from 72.5% to 110.5%, and the RSD was less than 20%. These results were validated by GC-MS, which indicated that this convenient and sensitive method has great potential for small molecular in real samples.

Antitumor Effects of Orally and Intraperitoneally Administered Chitosan Oligosaccharides (COSs) on S180‐Bearing/Residual Mouse

Chitosan oligosaccharides (COSs) are hydrolysate mixture of chitin and possess various biomedical properties, such as antimicrobial, immunoenhancing, and antitumor effects. Antiproliferation activity of COS and commercially available samples was compared in the terms of A549 and HCT-116 cells. Ten tumor cells were used to estimate cytotoxicity of COS. Although there were some researches on the antitumor effects of COS, we highlighted the in vivo antitumor activities of COS administrated orally and intraperitoneally on S180-bearing/residual mouse. Results turned out that in vitro IC50 values of COS were 48.6 ± 7.0 to 1329.9 ± 93.4 μg/mL against 10 different tumor cell lines. Then, the in vivo experiments proved that the inhibition rate was high up to 58.5%. Significant cell death and necrosis were observed in COS-treated groups by histological analysis. COS stimulated the mRNA expression of tumor necrosis factor alpha. In summary, COS may be considered promising candidate as antitumor functional food or pharmaceutic adjuvant in oncotherapy, especially for patients after surgical resection.

A rapid immunomagnetic-bead-based immunoassay for triazophos analysis

An immunomagnetic-bead-based enzyme-linked immunosorbent assay (IMB-ELISA) was developed for detection of pesticides by using carboxyl functionalized magnetic Fe3O4 nanoparticles (CMNPs). The CMNPs were prepared by co-precipitation of Fe2+/Fe3+ with oleic acid as a surfactant and subsequent oxidation of CC into COOH by KMnO4 solution in situ. Then, anti-pesticide (triazophos) monoclonal antibodies were directly bonded onto the magnetic nanoparticles, which significantly increased the sensitivity compared with classic ELISA. The detection limit was 0.10 ng mL−1. Addition-recovery and high-precision experiments were performed on blank samples that were determined to be without triazophos. The average recovery rate for three types of samples (with each spiking concentration measured 5 times in parallel) ranged from 83.1% to 115.9%, with a relative standard deviation (RSD) of less than 10%, which meets the requirement of pesticide residue analysis. The application results were in accordance with the gas chromatography-mass spectrometry (GC-MS) method, suggesting that IMB-ELISA is rapid and reliable for pesticide detection.

Study on Enhancement Principle and Stabilization for the Luminol-H2O2-HRP Chemiluminescence System

A luminol-H2O2-HRP chemiluminescence system with high relative luminescent intensity (RLU) and long stabilization time was investigated. First, the comparative study on the enhancement effect of ten compounds as enhancers to the luminol-H2O2-HRP chemiluminescence system was carried out, and the results showed that 4-(imidazol-1-yl)phenol (4-IMP), 4-iodophenol (4-IOP), 4-bromophenol (4-BOP) and 4-hydroxy-4’-iodobiphenyl (HIOP) had the best performance. Based on the experiment, the four enhancers were dissolved in acetone, acetonitrile, methanol, and dimethylformamide (DMF) with various concentrations, the results indicated that 4-IMP, 4-IOP, 4-BOP and HIOP dissolved in DMF with the concentrations of 0.2%, 3.2%, 1.6% and 3.2% could get the highest RLU values. Subsequently, the influences of pH, ionic strength, HRP, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol on the stabilization of the luminol-H2O2-HRP chemiluminescence system were studied, and we found that pH value, ionic strength, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol have little influence on luminescent stabilization, while HRP has a great influence. In different ranges of HRP concentration, different enhancers should be selected. When the concentration is within the range of 0~6 ng/mL, 4-IMP should be selected. When the concentration of HRP ranges from 6 to 25ng/mL, 4-IOP was the best choice. And when the concentration is within the range of 25~80 ng/mL, HIOP should be selected as the enhancer. Finally, the three well-performing chemiluminescent enhanced solutions (CESs) have been further optimized according to the three enhancers (4-IMP, 4-IOP and HIOP) in their utilized HRP concentration ranges.

The Rapid Screening of Triazophos Residues in Agricultural Products by Chemiluminescent Enzyme Immunoassay

A highly sensitive chemiluminescent enzyme immunoassay (CLEIA) method was developed in this study for efficient screening of triazophos residues in a large number of samples. Based on the maximum residue limits (MRLs) set by China and CAC for triazophos in different agro-products, the representative apple, orange, cabbage, zucchini, and rice samples were selected as spiked samples, and the triazophos at the concentrations of the MRL values were spiked to blank samples. Subsequently, the five samples with the spiked triazophos standard were measured by CLEIA 100 times, and the detection results indicated that the correction factors of the apple, orange, cabbage, zucchini, and rice were determined as 0.79, 0.66, 0.85, 0.76, and 0.91, respectively. In this experiment, 1500 real samples were detected by both the CLEIA and the GC-MS methods. With the GC-MS method, 1462 samples were identified as negative samples and 38 samples as positive samples. Based on the correction factors, the false positive rate of the CLEIA method was 0.13%, and false negative rate was 0. The results showed that the established CLEIA method could be used to screen a large number of real samples.

Determination of hymexazol in 26 foods of plant origin by modified QuEChERS method and liquid chromatography tandem-mass spectrometry

A rapid and sensitive method based on modified QuEChERS for hymexazol determination in 26 plant-derived foods using liquid chromatography tandem-mass spectrometry (LC-MS/MS) was developed. Variables affecting the separation (LC column, mobile phase additives) and clean-up effects of various dispersive phases, such as PSA, C18, GCB, MWCNTs, PEP-2, Al2O3, Florisil, and PVPP were evaluated. The method was validated using 26 matrices at spiked levels of 0.01 or 0.02, 0.05, 0.1, and 0.5mg/kg (0.05, 0.2, 0.5, and 1.0mg/kg for green tea). Mean recoveries were between 71.2% and 113.8%, and intra and inter-day precisions were below 14.8%. The limit of quantitation for 26 matrices ranged from 10 to 50μg/kg. Matrix-matched calibration was used. The method was subsequently applied for real sample analysis, and hymexazol was detected in a cucumber (below the LOQ) and was not detected in any other sample. The method is simple and effective, and meets the routine monitoring requirements for hymexazol residue in foods.

A sensitive chemiluminescence enzyme immunoassay based on molecularly imprinted polymers solid-phase extraction of parathion

The chemiluminescence enzyme immunoassay (CLEIA) method responds differently to various sample matrices because of the matrix effect. In this work, the CLEIA method was coupled with molecularly imprinted polymers (MIPs) synthesized by precipitation polymerization to study the matrix effect. The sample recoveries ranged from 72.62% to 121.89%, with a relative standard deviation (RSD) of 3.74-18.14%.The ratio of the sample matrix-matched standard curve slope rate to the solvent standard curve slope was 1.21, 1.12, 1.17, and 0.85 for apple, rice, orange and cabbage in samples pretreated with the mixture of PSA and C18. However, the ratio of sample (apple, rice, orange, and cabbage) matrix-matched standard-MIPs curve slope rate to the solvent standard curve was 1.05, 0.92, 1.09, and 1.05 in samples pretreated with MIPs, respectively. The results demonstrated that the matrices of the samples greatly interfered with the detection of parathion residues by CLEIA. The MIPs bound specifically to the parathion in the samples and eliminated the matrix interference effect. Therefore, the CLEIA method have successfully applied MIPs in sample pretreatment to eliminate matrix interference effects and provided a new sensitive assay for agro-products.

A review of enhancers for chemiluminescence enzyme immunoassay

ABSTRACT There is increasing interest for chemiluminescence (CL) detection with the characteristics of simplicity, low cost and high sensitivity, especially wide application of enhancersin CL detection to increased signals, prolonged luminescence time and enhanced intensity. In this review, the applications of primary enhancers and secondary enhancers were mainly described in the horseradish peroxidase–luminol system of CL enzyme immunoassay for light delay in the course of the reaction with improved sensitivity. The present review on enhancers covers the papers since 1983. Future research needs to develop novel enhancers with less interference and better performance. With wide utilization of enhancers in the CL system, the CL immunodetection technology showed a good potential and wide development prospects in food and medicine fields.

Preparation of magnetic metal organic framework composites for the extraction of neonicotinoid insecticides from environmental water samples

MOF-199/Fe3O4 nanoparticles were explored for the first time to purify environmental water samples and adsorb neonicotinoid insecticides as hybrid adsorbents. The composites were successfully synthesized by an in situ method at room temperature with electrostatic interaction to chemically stabilize the nanoparticles and metal ions. The nanoparticles were uniformly encoded with metal organic frameworks (MOFs). With the lowest loading amount of Fe3O4 applied to magnetic solid-phase extraction (MSPE) of six neonicotinoid insecticides in environmental water samples followed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis, the extraction efficiency was the highest. The main influencing factors including the solution ionic strength, solution pH, extraction time, desorbing organic solvent, and solvent volume, were also evaluated. Considering the adsorbing conditions and insecticide structures, the adsorbing mechanism was preliminarily discovered to be largely dependent upon the π–π interaction with the benzene ring in MOF-199 and delocalized large π bonds in the insecticide molecules. Under optimal conditions, the limits of detection (LODs) were 0.3–1.5 ng mL−1 with a signal-to-noise ratio (S/N) of 3. All the analytes exhibited good linearity with correlation coefficients (r2) of higher than 0.9947. The relative standard deviations (RSDs) for six neonicotinoid insecticides in environmental samples in five replicates ranged from 1.5% to 11.6%, and good recoveries from 88.0% to 107.0% were obtained, indicating that the MOF-199/Fe3O4 composites are feasible for analysis of trace analytes in environmental water samples.

Determination of astaxanthin in feeds using high performance liquid chromatography and an efficient extraction method

ABSTRACT A high performance liquid chromatography method using an efficient extraction method was developed for the determination of astaxanthin in eight kinds of animal feed. The chromatographic separation was achieved using a C18 reversed-phase column, using methanol and acetonitrile as the mobile phases with a flow rate of 1 mL/min. The feeds containing astaxanthin were first treated with maxatase, to cause enzymatic hydrolysis, and then extracted with dichloromethane. The optimized method produced recoveries of between 82.4% and 100% for all eight kinds of feed, and the coefficients of variation were lower than 4.28%. The limit of detection, defined as the concentration that gave a signal-to-noise ratio of 3, for astaxanthin was estimated to be 0.1 µg/g. The limit of quantification, defined as the lowest spiked concentration that gave an appropriate level of precision and accuracy, was 0.3 µg/g. Finally, the method developed was used to determine astaxanthin in real, commercially sourced, feed samples. The method met the requirements for the determination of astaxanthin in feed, providing satisfactory recoveries of 70–110%. GRAPHICAL ABSTRACT