Qingmei Li

Rapid and Sensitive Detection of the Food Allergen Glycinin in Powdered Milk Using a Lateral Flow Colloidal Gold Immunoassay Strip Test

A rapid immunochromatographic lateral flow test strip in a sandwich format was developed with the colloidal gold-labeled mouse antiglycinin monoclonal antibody (mAb) and rabbit antiglycinin polyclonal antibody (pAb) to specifically identify glycinin, a soybean allergen. The test strip is composed of a sample pad, a conjugate reagent pad, an absorbent pad, and a test membrane containing a control line and a test line. This test strip has high sensitivity, and results can be obtained within 10 min without sophisticated procedures. The limit of detection (LOD) of the test strip was calculated to be 0.69 mg/kg using an optical density scanner that measures relative optical density. The assay showed high specificity for glycinin, with no cross-reactions with other soybean proteins or other food allergens. The recoveries of the lateral flow test strip in detecting glycinin in powdered milk samples ranged between 80.5 and 89.9% with relative standard deviations of less than 5.29% (intra-assay) and 6.72% (interassay). Therefore, the test strip is useful as a quantitative, semiquantitative, or qualitative detection method for glycinin in powdered milk. In addition, the test strip can be used to detect glycinin in other processed foods and may be a valuable tool in identifying effective approaches for reducing the impact of glycinin.

Development of a One-Step Strip Test for the Diagnosis of Chicken Infectious Bursal Disease

Abstract A rapid diagnostic strip for chicken infectious bursal disease (IBD) was developed based on membrane chromatography using high-affinity monoclonal antibodies directed to chicken infectious bursal disease virus (IBDV). The diagnostic strip has high specificity for detection of chicken IBDV antigen and recognizes a variety of the virus isolates, including virulent and attenuated strains, with no cross-reactivity to other viruses, such as Newcastle disease virus, Mareks disease virus, infectious bronchitis virus, infectious laryngotracheitis virus, and egg-drop-syndrome virus. The results showed that its specificity was highly consistent with the agar-gel precipitation test (AGP). The diagnostic strip detected as low as 800 median egg lethal dose (ELD50) viruses in the IBDV BC6/85-infected sample, which was comparable with AC-ELISA (400 ELD50) and 32 times more sensitive than the AGP test (2.56 × 104 ELD50). In experimental infection, IBDV was detected in the bursa as early as 36 hr postinfection with the diagnostic strip before the clinical signs and gross lesions appeared. It takes only 1–2 min to do a strip test to detect chicken IBDV antigen after the specimen is grounded in a whirl pack with finger massage.

Identification of the linear epitope for Fc‐binding on the bovine IgG2 Fc receptor (boFcγ2R) using synthetic peptides

To identify the linear epitope for Fc‐binding on the bovine IgG2 Fc receptor (boFcγ2R), peptides derived from the membrane‐distal extracellular domain (EC1) of boFcγ2R corresponding to the homologous region of human FcαRI were synthesized. Binding of bovine IgG2 to the different peptides was tested by Dot‐blot assay, and the peptide showing maximal binding was further modified by truncation and mutation. The minimum effective peptide 82FIGV85 located in the putative F–G loop of the EC1 domain was found to bind bovine IgG2 specifically and inhibit the binding of bovine IgG2 to the receptor. The Phe82, Ile83 and Val85 residues within the linear epitope were shown to be critical for IgG2‐binding. Such functional epitope peptide should be very useful for understanding the IgG‐Fcγ interaction and development of FcR‐targeting drugs.

Development of a colloidal gold-based strip test for the detection of chlorothalonil residues in cucumber

An immunochromatographic lateral flow strip test using the competitive format was developed for the determination of chlorothalonil (CTN) residues in cucumber. The limit of detection was less than 100 ng/mL by visual assessment and was found to be 91.78 ± 0.17 ng/mL for quantitative detection using a test strip reader. The recoveries of test samples were from 89.26% to 102.02% and the coefficient of variation (%) was less than 4.75%. Parallel analysis of cucumber samples with CTN showed comparable results from the strip test and high performance liquid chromatography. The strip test requires 5–8 min to complete and provides a very useful screening method for the quantitative and qualitative detection of CTN residues in cucumber.

Colloidal gold˗McAb probe˗based rapid immunoassay strip for simultaneous detection of fumonisins in maize

BACKGROUND Fumonisins are a kind of toxic and carcinogenic mycotoxin. A rapid immunochromatographic test strip has been developed for simultaneous detection of fumonisin B1 , B2 and B3 (FB1 , FB2 and FB3 ) in maize based on colloidal gold-labelled monoclonal antibody (McAb) against FB1 probe. RESULTS The anti-FB1 McAb (2E11-H3) was produced through immunisation and cell fusion, and identified as high affinity, specificity and sensitivity. The cross-reaction ratios with fumonisin B2 and B3 were accordingly 385% and 72.4%, while none with other analogues. The colloid gold-labelled anti-FB1 McAb probe was successfully prepared and used for establishing the immunochromatographic strip. The test strip showed high sensitivity and specificity, the IC50 for FB1 was 58.08 ng mL-1 , LOD was 11.24 ng mL-1 , calculated from standard curve. Moreover, the test strip exhibited high cross-reactivity with FB2 and FB3 , and could be applied to the simultaneous detection of FBs (FB1 :FB2 :FB3 = 12:4:1) in maize sample with high accuracy and precision. The average recoveries of FBs in maize ranged from 90.42% to 95.29%, and CVs were 1.25-3.77%. The results of the test strip for FBs samples showed good correlation with high-performance liquid chromatography analysis. CONCLUSION The immunochromatographic test strip could be employed in the rapid simultaneous detection of FB1 , FB2 and FB3 in maize samples on-site.

Development of an immunochromatographic lateral flow strip for the simultaneous detection of aminoglycoside residues in milk

A colloidal gold-based immunochromatographic strip with a competitive format has been developed for the rapid, simultaneous, semi-quantitative and quantitative detection of several aminoglycoside residues in milk, including gentamicin sulfate (GM), neomycin sulfate (NEO) and kanamycin sulfate (KN). Three monoclonal antibodies against the three corresponding aminoglycosides were conjugated to colloidal gold particles and applied to the conjugate pads of the strip. The competitors [GM-bovine serum albumin (GM-BSA), NEO-BSA and KN-BSA conjugates] of GM, NEO and KN were immobilized onto a nitrocellulose (NC) membrane at three detection zones, T1, T2, and T3, respectively. The minimal cut-off values of the strip were 10 ng mL−1 for GM, and 100 ng mL−1 for NEO and KN, which are lower than the maximum residue levels (MRLs) established for aminoglycosides. The IC50 values of the strip were 0.737 ng mL−1, 8.971 ng mL−1 and 11.110 ng mL−1 for GM, NEO and KN respectively. In conclusion, the immunochromatographic lateral flow strip could be used for rapid, simultaneous, semi-quantitative and quantitative detection of GM, NEO and KN residues in milk.