Lingling Guo

Development of monoclonal antibody and lateral test strip for sensitive detection of clenbuterol and related β2-agonists in urine samples

Being the most used and preferred β2-agonist, clenbuterol (CLB) has been reported to be illegally abused in animal production and breeding as it improves growth rate while inhibiting fat synthesis and deposition leading to buildup of lean muscle. Due to its potential hazard to human health, causing food poisoning that can be fatal, it has been forbidden as a growth promoter for food-producing animals in most countries including China. Therefore, frequent monitoring of CLB abuse is necessary for consumer safety against its residues. We therefore report development of a monoclonal antibody and lateral flow test strip for sensitive detection of CLB in urine samples. In this investigation, male BALB/C mice were first immunized for antibody production. Thereafter, gold nanoparticles were utilized for antigen and antibody immobilization during construction of the strip. Under optimized conditions, the cut-off limit of the test strip was found to be 2.5 and 5 ng/g in phosphate-buffered saline (PBS) and urine using the wet method. When the dry method was used for CLB detection, the cut-off limit of the test strip in PBS and urine was found to be 3 ng/g. Each test was evaluated within 6 min. The data obtained show that the strip developed is sensitive and has an advantage of fast test results and simplicity and hence can be adopted for screening of CLB residues in urine samples for mitigation of CLB residue effects to human health.

Development of an enzyme-linked immunosorbent assay for dibutyl phthalate in liquor.

A monoclonal antibody specifically recognizing dibutyl phthalate (DBP) was prepared based on a hapten (di-n-butyl-4-aminophthalate). After optimizing various parameters such as concentrations of antibody, coating antigen and composition of the assay buffer, an inhibition curve was plotted with the 50% inhibition concentration value (IC50) 33.6 ± 2.5 ng/mL. A low level of cross-reactivity (<5%) was found for other phthalate esters. Recovery tests were conducted using liquor simulant (a mixture of water and ethanol) at two fortification levels (100 ng/mL and 300 ng/mL). The recovery rates ranged from 84.7% to 94.5% with a coefficient of variation between 7.1% and 12.8%. Nine liquor samples of different alcoholic strengths were detected using the proposed measure and confirmatory analysis was performed using liquid chromatography-mass spectroscopy (LC-MS). The detection results showed good consistency between the two measures and all the data above indicated that the proposed ELISA could be applied in DBP screening.

Comparsion of an immunochromatographic strip with ELISA for simultaneous detection of thiamphenicol, florfenicol and chloramphenicol in food samples.

Rapid and sensitive indirect competitive enzyme-linked immunosorbent assays (ic-ELISA) and gold nanoparticle immunochromatographic strip tests were developed to detect thiamphenicol (TAP), florfenicol (FF) and chloramphenicol (CAP) in milk and honey samples. The generic monoclonal antibody for TAP, FF and CAP was prepared based on a hapten [D-threo-1-(4-aminophenyl)-2- dichloroacetylamino-1,3-propanediol], and the haptenwas linked to a carrier protein using the diazotization method. After the optimization of several parameters (coating, pH, sodium chloride content and methanol content), the ic-ELISA was established. The quantitative working range for TAP was 0.11-1.36 ng/mL, with an IC50 of 0.39 ng/mL. The optimized ELISA showed cross-reactivity to CAP (300%) and FF (15.6%), with IC50 values of 0.13 and 2.5 ng/mL, respectively. The analytical recovery of TAP, FF and CAP in milk and honey samples in the ic-ELISA ranged from 81.2 to 112.9%. Based on this monoclonal antibody, a rapid and sensitive immunochromatographic test strip was also developed. This strip had a detection limit of 1 ng/mL for TAP, FF and CAP in milk and honey samples. Moreover, the test was completed within 10 min. Our results showed that the proposed ic-ELISA and immunochromatographic test strip method are highly useful screening tools for TAP, FF and CAP detection in milk and honey samples.

Development of an ELISA for nitrazepam based on a monoclonal antibody

We report the production of a specific monoclonal antibody against Nitrazepam (NZP). First, the hapten 7-aminonitrazepam (7-ANZP) was synthesized, then the hapten was coupled with bovine serum albumin and ovalbumin by the diazotization method, and used as immunogen and coating antigen. Factors affecting binding, ionic strength, pH, and methanol concentration in phosphate-buffered saline, were optimized. The monoclonal antibody had a satisfactory IC50 of 0.2 ng/mL for NZP. The cross-reactivities with other analogs were all lower than 0.1% except for 23% with 7-NZP, which suggested that the enzyme-linked immunosorbent assay method possessed high specificity. The recoveries were in the range of 84–95%, indicating that the method could be applied for the detection of NZP in urine.

Simultaneous detection of tylosin and tilmicosin in honey using a novel immunoassay and immunochromatographic strip based on an innovative hapten

ABSTRACT Tylosin (TYL) and tilmicosin (TIM) are macrolide antibiotics, and maximum residue limits (MRLs) have been set to control their illegal usage in food. We developed a sensitive indirect competitive enzyme-linked immunosorbent assay and rapid immunochromatographic strip (ICS) test to simultaneously detect TYL and TIM based on an innovative hapten (TYL-carboxymethoxylamine hemihydrochloride). The monoclonal antibody 2B3 was obtained with the isotype IgG1, and TYL and TIM had half maximal inhibitory concentrations of 0.57 and 2.10 ng/ml, respectively. The cross-reactivity values were 100%, 27.57%, 97.43%, and 62.42% for TYL, TIM, desmycosin, and acetylisovaleryl tylosin, respectively. By optimizing, the standard dilution buffer was based on 0.8% NaCl, pH 7.4 and 5% acetonitrile. The recoveries ranged from 89.37% to 112.00% in the honey samples, which suggests that the assay would be reliable in the analysis of real honey samples. In addition, an ICS was developed for qualitative, semi-quantitative, and spot detection analysis, with cut-off values of 5 and 15 ng/ml for TYL and TIM in phosphate-buffered saline, and 10 and 20 ng/ml for TYL and TIM in honey, respectively. The results show that these assays can be used to analyze real samples with the strictest MRL being 50 ng/ml for both TYL and TIM.

Ultrasensitive Immunochromatographic Strip for Fast Screening of 27 Sulfonamides in Honey and Pork Liver Samples Based on a Monoclonal Antibody

Group-specific monoclonal antibodies (Mabs) with selectivity for 27 sulfonamides were developed based on new combinations of immunogen and coating antigen. The Mab was able to recognize 27 sulfonamides with 50% inhibition concentration (IC50) values ranging from 0.15 to 15.38 μg/L. In particular, the IC50 values for five sulfonamides (sulfamethazine, sulfaquinoxaline, sulfamonomethoxine, sulfadimethoxine, and sulfamethoxazole) were 0.51, 0.15, 0.56, 0.54, and 2.14 μg/L, respectively. On the basis of the Mab, an immunochromatographic lateral flow strip test was established for rapid screening of sulfonamides in honey samples. The visual limit of detection of the strip test for most sulfonamides in spiked honey samples was below 10 μg/kg, satisfying the requirements of authorities. Positive honey and pork liver samples, which had been confirmed by high-performance liquid chromatography/mass spectrometry, were used to validate the reliability of the proposed strip test. The immunochromatographic lateral flow strip test provides a rapid and convenient method for fast screening of sulfonamides in honey samples.

Preparation of an anti-dexamethasone monoclonal antibody and its use in development of a colloidal gold immunoassay

ABSTRACT A lateral flow colloidal gold (CG) immunoassay strip has been developed for detection of dexamethasone (DEX) residues in milk samples. For this purpose, an anti-DEX monoclonal antibody (McAb), based on a DEX succinic anhydride derivative hapten, was prepared and characterized. The McAb showed a high specificity to DEX, the half inhibitory concentration of the antibody was 0.095 ng/mL, its limit of detection (LOD) was 0.017 ng/mL, and its linear range of detection was 0.034–0.265 ng/mL. The developed CG immunoassay had a visual cut-off value of 0.3 ng/mL in phosphate buffered saline (PBS) and 0.5 ng/mL in milk samples. Each test requires 10 min. Analysis of DEX in milk indicated that the results of strip assay had a strong agreement with indirect competitive enzyme-linked immunosorbent assay. Therefore, the CG immunoassay is a sensitive screening method for semi-quantitative and qualitative detection of DEX residues in milk samples.

Development of an immunochromatographic strip for the rapid detection of maduramicin in chicken and egg samples

ABSTRACT Following the steps of antigen synthesis, immunization, cell fusion, ascites preparation and purification, a maduramicin (MD) monoclonal antibody (mAb) was produced. This MD-mAb demonstrated a 50% inhibition concentration value of 3.75 ng/ml, an affinity constant of 3.70  × 1010 l/mol, and the isotype was IgG3. The MD-mAb has no cross-reactivity with other polyether antibiotics. Using this MD-mAb, a gold immunochromatographic assay was developed to detect MD residues in chicken breast and egg samples. For semi-quantitative detection by the naked eye, the visual limit of detection was 5 ng/g in chicken breast, 10 ng/g in egg. Quantitative results can be obtained by a hand-held strip scan reader, with the detection range of 5.11–19.34 ng/g in chicken breast and 6.46–27.87 ng/g in egg. The strip test took 10 min to run in total. This strip assay is suitable for on-site detection of MD residues in chicken breast and egg samples.

Gold Nanoparticle‐Based Paper Sensor for Simultaneous Detection of 11 Benzimidazoles by One Monoclonal Antibody

A colloidal gold immunochromatographic assay based on a generic monoclonal antibody is developed for the simultaneous detection of benzimidazoles and metabolite residues in milk samples. The monoclonal antibody is prepared using 2-(methoxycarbonylamino)-3H-benzimidazole-5-carboxylic acid as the hapten, and it can recognize 11 types of benzimidazoles simultaneously. The immunochromatographic strip is assembled and labeled using gold nanoparticles. This strip can detect 11 benzimidazoles including albendazole, albendazole s-oxide, albendazole sulfone, fenbendazole, fenbendazole sulfone, flubendazole, mebendazole, parbendazole, oxfendazole, oxibendazole, and carbendazim within 15 min in milk samples. Results are obtained visually with the naked eye, and the cutoff values and the visual limit of detection values for these benzimidazoles are 25, 6.25, 12.5, 12.5, 50, 25, 50, 50, 50, 6.25, and 25 ng mL-1 , and 6.25, 3.125, 3.125, 1.56, 12.5, 6.25, 12.5, 12.5, 6.25, 0.78, and 12.5 ng mL-1 , respectively. Results are also obtained using a hand-held strip scan reader, with calculated limit of detection values for these benzimidazoles of 0.83, 0.77, 1.83, 0.98, 7.67, 3.50, 3.96, 5.71, 0.92, 0.59, and 1.69 ng mL-1 , respectively. In short, the developed paper sensor is a useful tool for rapid and simple screening of residues of benzimidazoles in milk samples.

Colloidal gold-based immunochromatographic strip assay for the rapid detection of three natural estrogens in milk

In this study, we developed highly sensitive and specific monoclonal antibodies (mAbs) against estrone (E1), 17β-estradiol (17β-E2), and estriol (E3). The half-maximal inhibitory concentration values of anti-E1, anti-17β-E2, and anti-E3 mAbs were 0.46, 0.36, and 0.39 ng/mL, respectively, based on competitive enzyme-linked immunosorbent assay (ic-ELISA) results. A rapid colloidal gold-based immunoassay strip assay was developed for the determination of E1, 17β-E2, and E3 residues in milk samples. The assay had a visual cut-off value of 5 ng/mL, and required 10 min to assess with the naked eye. The results obtained from the immunochromatographic strip assay were consistent with those obtained from ic-ELISA and gas chromatography-mass spectrometry. The immunochromatographic strip assay is useful and rapid for the detection of E1, 17β-E2, and E3 in milk.