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Toxins 2014, 6(12), 3208-3222;

Uniform Orientation of Biotinylated Nanobody as an Affinity Binder for Detection of Bacillus thuringiensis (Bt) Cry1Ac Toxin

2,* and 1,3,*
The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Sipailou NO. 2, Southeast University, Nanjing 210096, China
Institute of Food Safety, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
Jiangsu Nanobody Engineering and Research Center, Nantong 226010, China
These authors contributed equally to this work.
Authors to whom correspondence should be addressed.
Received: 11 October 2014 / Revised: 10 November 2014 / Accepted: 17 November 2014 / Published: 2 December 2014
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Nanobodies are the smallest natural fragments with useful properties such as high affinity, distinct paratope and high stability, which make them an ideal tool for detecting target antigens. In this study, we generated and characterized nanobodies against the Cry1Ac toxin and applied them in a biotin-streptavidin based double antibodies (nanobodies) sandwich-ELISA (DAS-ELISA) assay. After immunizing a camel with soluble Cry1Ac toxin, a phage displayed library was constructed to generate Nbs against the Cry1Ac toxin. Through successive rounds of affinity bio-panning, four nanobodies with greatest diversity in CDR3 sequences were obtained. After affinity determination and conjugating to HRP, two nanobodies with high affinity which can recognize different epitopes of the same antigen (Cry1Ac) were selected as capture antibody (Nb61) and detection antibody (Nb44). The capture antibody (Nb61) was biotinylated in vivo for directional immobilization on wells coated with streptavidin matrix. Both results of specificity analysis and thermal stability determination add support for reliability of the following DAS-ELISA with a minimum detection limit of 0.005 μg·mL−1 and a working range 0.010–1.0 μg·mL−1. The linear curve displayed an acceptable correlation coefficient of 0.9976. These results indicated promising applications of nanobodies for detection of Cry1Ac toxin with biotin-streptavidin based DAS-ELISA system. View Full-Text
Keywords: nanobody; Cry1Ac toxin; streptavidin; DAS-ELISA nanobody; Cry1Ac toxin; streptavidin; DAS-ELISA

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Li, M.; Zhu, M.; Zhang, C.; Liu, X.; Wan, Y. Uniform Orientation of Biotinylated Nanobody as an Affinity Binder for Detection of Bacillus thuringiensis (Bt) Cry1Ac Toxin. Toxins 2014, 6, 3208-3222.

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