Huihua Qu

Rapid lateral-flow immunoassay for the quantum dot-based detection of puerarin

In this study, a rapid (within 10min) quantitative lateral-flow immunoassay using a quantum dots (QDs)-antibody probe was developed for the analysis of puerarin (PUE) in water and biological samples. The competitive immunoassay was based on anti-PUE monoclonal antibody conjugated with QDs (detection reagent). Secondary antibody was immobilized on one end of a nitrocellulose membrane (control line) and PUE-bovine serum albumin conjugate was immobilized on the other end (test line). In the quantitative experiment, the detection results were scanned using a membrane strip reader and a detection curve (regression equation: y=-0.11ln(x)+0.979, R(2)=0.9816) representing the averages of the scanned data was obtained. This curve was linear from 1 to 10μg/mL. The IC50 value was 75.58ng/mL and the qualitative detection limit of PUE was 5.8ng/mL. The recovery of PUE added to phosphate-buffered saline and biological samples was in the range of 97.38-116.56%. To our knowledge, this is the first report of the quantitative detection of a natural product by QDs-based immunochromatography, which represents a powerful tool for rapidly screening PUE in plant materials and other biological samples.

Development of an enzyme-linked immunosorbent assay based on anti-puerarin monoclonal antibody and its applications

An enzyme-linked immunosorbent assay (ELISA) was developed, and its application in immunoaffinity column chromatography was studied using a monoclonal antibody (MAb) against puerarin. Splenocytes isolated from a female BALB/c mouse immunised with a puerarin-bovine serum albumin (BSA) conjugate were fused with SP2/0 myeloma cells. The hybridoma cell line secreting MAb against puerarin (AA9) was acquired by screening and limiting dilution. The antibody generated was highly specific for puerarin with <0.01% cross-reactivity with over 50 structurally related chemicals, except for baicalein (51.8%). Using AA9, we developed an immunoassay for puerarin with a linear detection range of 10ng/ml to 1μg/ml. This assay system was further validated using intra- and inter-assays and recovery experiments. In addition, puerarin levels in both formulated Chinese medicines and biological samples were determined with high sensitivity and efficiency. Finally, we developed and validated protocols for knocking puerarin out of its parent medicine completely. In conclusion, we successfully developed a reliable ELISA and an immunoaffinity column for puerarin detection and knockout, which are useful tools for exploring the role of puerarin in formulated Chinese medicines.

Development of ELISA for detection of Rh1 and Rg2 and potential method of immunoaffinity chromatography for separation of epimers.

In this work, hybridomas producing anti-ginsenoside-Rh1 monoclonal antibodies (MAbs) were generated. These MAbs were subsequently used to create indirect competitive enzyme-linked immunosorbent assays (icELISAs). A linear correlation was obtained for G-Rh1 concentrations in the range from 26 to 512ng/mL. The regression equation was y=1.979-0.201Log2(X) with a regression coefficient of 0.9898. Precision and accuracy of the icELISA method were evaluated by the variations between replicates from well to well (intra-assay) and plate to plate (inter-assay). The recovery rates ranged from 93.16% to 108.43%. Testing with the icELISA demonstrated that the MAbs were specific for 20(S)-Rh1 and 20(S)-Rg2 with no cross-reactivity against 20(R)-Rh1 and 20(R)-Rg2. The immunoaffinity chromatography column (IAC) was constructed by covalently coupling monoclonal antibody (MAb) against G-Rh1 to CNBr-activated Sepharose 4B. When 20(R)-type-Rg2 passed through the IAC column, it was adsorbed, but the amount adsorbed was lower than that when 20(S)-type-Rg2 ran through the column. The differences in adsorption between the 20(S) and 20(R) type ginsenosides bring a new approach or method to separate 20(S)-Rg2 and 20(R)-Rg2 by IAC. Our results indicate that the icELISA is a sensitive and efficient approach for the identification of epimers, and the application of IAC using MAbs against small molecules provides a totally new thought and potential method for resolving epimers.

Establishment of an enzyme-linked immunosorbent assay and application on determination of ginsenoside Re in human saliva.

This work describes an immunochemical approach for the quality control of Panax ginseng and a pharmacological study of ginsenoside Re, a major bioactive constituent in P. ginseng, using an enzyme-linked immunosorbent assay. A hybridoma secreting monoclonal antibody against ginsenoside Re was produced by fusing splenocytes immunized with a ginsenoside Re-bovine serum albumin conjugate with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma SP2/0 cell line. The method, at an effective measuring range of 7.8-500 ng · mL(-1) of ginsenoside Re, successfully detected ginsenoside Re in Chinese traditional herb prescriptions. The results demonstrate that we generated a novel and reliable assay system for measuring ginsenoside Re in Chinese medicines more efficiently. Futhermore, we determined the ginsenoside Re concentrations in the saliva of six healthy adults after the oral administration of a ginseng capsule to study the pharmacokinetics of ginsenoside Re in human saliva.

Assessment of baicalin in mouse blood by monoclonal antibody-based icELISA

An indirect competitive enzyme-linked immunosorbent assay (icELISA) based on monoclonal antibaodies (MAb) was recently developed. This new method displays high sensitivity and accuracy, and is especially suitable for pharmacokinetic studies in small laboratory animals. This study aimed to develop an icELISA procedure for baicalin (BAL) quantitation in blood. We successfully developed the icELISA and applied in pharmacokinetic assays of Gegen Qinlian Decoction in mice. A linear correlation was obtained for BAL concentrations in the range from 34.69 to 2220.00 µg/L. The regression equation was y = 1.5557 - 0.4028log(C) with a correlation coefficient of 0.9936. Precision and accuracy of the icELISA method were evaluated by the variations between replicates from well to well (intra-assay) and plate to plate (inter-assay). The values obtained for these parameters were within the normal range (<15%). The recovery rates ranged from 98.93 to 126.78%, meeting the requirements for biological samples. Stability studies showed that BAL sample solutions were intact for 1 h, enough time for UV detection. However, long-term storage and especially freeze-thaw procedures were detrimental to BAL. The pharmacokinetic parameters derived from mouse experiments were as follows: area under the curves from time 0 to 48 h, 1876.15 ± 1108.14 mg h/L; mean maximum blood concentrations, 101.09 ± 31.53 mg/L; time of maximum concentration, 3.58 ± 2.88 h; mean residence time, 79.30 ± 61.21 h.

Development of an enzyme‐linked immunosorbent assay and immunoaffinity chromatography for glycyrrhizic acid using an anti‐glycyrrhizic acid monoclonal antibody

In this work, a new monoclonal antibody specific for glycyrrhizic acid was prepared and characterized. A hybridoma secreting an anti-glycyrrhizic acid monoclonal antibody was produced by fusing splenocytes from a mouse immunized against a glycyrrhizic acid-bovine serum albumin conjugate with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma cell line (Sp2/0-Ag14). Subsequently, an indirect, competitive enzyme-linked immunosorbent assay for glycyrrhizic acid was developed using the monoclonal antibody. In this assay, we detected an effective measuring range of 78.12-2500 ng/mL. Both intra-assay and inter-assay repeatability and precision were achieved, with relative standard deviations lower than 10%. In addition, glycyrrhizic acid levels in both formulated Chinese medicines and biological samples were determined with high sensitivity and efficiency. We then successfully developed a reliable immunoaffinity chromatography to separate glycyrrhizic acid completely from its parent medicine. These methods will contribute to further research investigations to better understand the interactions of glycyrrhizic acid with other drugs in the complex system of traditional Chinese medicine.

Rapid, sensitive separation of the three main isoflavones in soybean using immunoaffinity chromatography

Daidzin, genistin, and glycitein are major isoflavone compounds in soybean that are indispensable nutrients in traditional Chinese foods. Generally, strategies for detecting and separating soy isoflavones have been based on HPLC and chromatographic techniques, which are tedious and time-consuming procedures. In the present study, we developed an ELISA-based approach for daidzin detection using a broad-specificity monoclonal antibody (clone number: AA9) with an effective detection range of 10-10 000 ng/mL. Subsequently, we prepared an immunoaffinity column by coupling the monoclonal antibody AA9 to CNBr-activated Sepharose 4B. Our results demonstrate that the immunoaffinity column can efficiently and specifically extract daidzin, glycitein, and genistin from numerous structurally similar soy isoflavones in leguminous plants, thereby providing a new method for the extraction of target components from similar compounds in natural products.

A Sensitive and Specific Indirect Competitive Enzyme-Linked Immunosorbent Assay for Detection of Paeoniflorin and Its Application in Pharmacokinetic Interactions between Paeoniflorin and Glycyrrhizinic Acid.

This study aimed to develop an indirect competitive enzyme-linked immunosorbent assay based on monoclonal antibodies against paeoniflorin to study the effects of different doses of glycyrrhizinic acid on the pharmacokinetics of paeoniflorin in mice. An anti-paeoniflorin monoclonal antibody was produced from a hybridoma created through a fusion of splenocytes immunized with paeoniflorin-bovine serum albumin and conjugated with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma cell line SP2/0. The resultant antibody was used to develop and validate a rapid, specific and sensitive, indirect competitive enzyme-linked immunosorbent assay for the measurement of paeoniflorin (linear range 4.8-312.5 ng · mL(-1)). The intraday and interday precision values of the indirect competitive ELISA method were well within the recommended range (≤ 10 %), and the recovery rate was, on average, 101.13 %. Pharmacokinetic parameters obtained from mouse blood samples at various intervals following the oral administration of paeoniflorin and glycyrrhizic acid at three doses (1 : 0.3, 1 : 1, 1 : 3, respectively) demonstrated that the highest dose of glycyrrhizic acid inhibits the absorption of paeoniflorin.

Enzyme-Linked Immunosorbent Assay for Hyodeoxycholic Acid in Pharmaceutical Products Using a Monoclonal Antibody

Herein is reported an immunochemical approach to determine hyodeoxycholic acid using hybridoma-secreting monoclonal antibodies. The hyodeoxycholic acid-specific antibody was produced by fusing splenocytes immunized with a hyodeoxycholic acid-bovine serum albumin conjugate with a hypoxanthine–aminopterin–thymidine-sensitive mouse myeloma cell line (SP2/0). The antibody was highly specific for hyodeoxycholic acid, with less than 0.05 percent cross-reactivity to over fifty structurally related compounds. The antihyodeoxycholic acid monoclonal antibody was then used to develop a rapid, specific, and sensitive indirect competitive enzyme-linked immunosorbent assay (icELISA) for the determination of hyodeoxycholic acid in pharmaceutical compounds. The linear dynamic range was from 0.48 to 62.5 nanograms per milliliter with an IC50 value of 8 nanograms per milliliter. The icELISA results correlated well with a conventional high-performance liquid chromatography method for the determination of hyodeoxycholic acid (R2 = 0.9982). This study shows that the icELISA method was successfully applied to the quantification of hyodeoxycholic acid in pharmaceutical products.

Effect of puerarin on the pharmacokinetics of baicalin in Gegen Qinlian Decoction (葛根芩连汤) in mice

ObjectiveTo study the pharmacokinetics of puerarin (PUE) in Gegen Qinlian Decoction (葛根芩连汤, GQD), and the effects of PUE dosage variations on the pharmacokinetics of baicalin (BAL) in mice.MethodsGQD is composed of the concentrated granules of four Chinese herbs. Three dosages with different levels of PUE, including GQD, GQD co-administered with PUE, and GQD co-administration with two times the amount of PUE, were used to research the pharmacokinetics of PUE and BAL in mice. The indirect competitive enzyme-linked immunosorbent assay (icELISA) methods based on an anti PUE-monoclonal antibody (MAb)and BAL-MAb were employed to determine the concentration of PUE and BAL in mice blood.ResultsAfter the co-administration of GQD with PUE, the area under the curves (AUC0–14h) of PUE increased 2.8 times compared with GQD. At the dose of GQD co-administration at two times that of PUE, the (AUC0–14h) of PUE was almost equal to that of GQD co-administration of PUE, showing non-linear pharmacokinetics. The (AUC0–48h) of BAL showed a good dose-related increase of PUE (r=0.993) in the range from 100 to 300 mg/kg, indicating that PUE dramatically affects the absorption of BAL in mice. There was no significant difference in the other pharmacokinetic parameters, such as the first time of maximum concentration (Tmax), the second Tmax, or the mean residence time.ConclusionsThe icELISA methods were successfully applied to pharmacokinetic studies of PUE and BAL in GQD in mice. The dosage variability of PUE of the main ingredient in GQD affects its own pharmacokinetic characteristics and the absorption characteristics of BAL.