Poly-protein G-expressing bacteria enhance the sensitivity of immunoassays

Wen Rui Hao, Michael Chen, Yi Jou Chen, Yu-Cheng Su, Chiu Min Cheng, Hsiang Yin Hsueh, An Pei Kao, Yuan Chin Hsieh, Johny Chang, Ming Yang Tseng, Kuo Hsiang Chuang*

*Corresponding author for this work

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The sensitivities of solid-phase immunoassays are limited by the quantity of detection antibodies bound to their antigens on the solid phase. Here, we developed a poly-protein G-expressing bacterium as an antibody-trapping microparticle to enhance the signals of immunoassays by increasing the accumulation of detection antibodies on the given antigen. Eight tandemly repeated fragment crystallisable (Fc) binding domains of protein G were stably expressed on the surface of Escherichia coli BL21 cells (termed BL21/8G). BL21/8G cells showed a higher avidity for trapping antibodies on their surface than monomeric protein G-expressing BL21 (BL21/1G) cells did. In the sandwich enzyme-linked immunosorbent assay (ELISA), simply mixing the detection antibody with BL21/8G provided a detection limit of 6 pg/mL for human interferon-α (IFN-α) and a limit of 30 pg/mL for polyethylene glycol (PEG)-conjugated IFN-α (Pegasys), which are better than that of the traditional ELISA (30 pg/mL for IFN-α and 100 pg/mL for Pegasys). Moreover, the sensitivity of the Western blot for low-abundance Pegasys (0.4 ng/well) was increased by 25 folds upon mixing of an anti-PEG antibody with BL21/8G cells. By simply being mixed with a detection antibody, the poly-protein G-expressing bacteria can provide a new method to sensitively detect low-abundance target molecules in solid-phase immunoassays.

Original languageEnglish
Article number989
JournalScientific reports
Issue number1
StatePublished - 1 Dec 2017

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    Hao, W. R., Chen, M., Chen, Y. J., Su, Y-C., Cheng, C. M., Hsueh, H. Y., Kao, A. P., Hsieh, Y. C., Chang, J., Tseng, M. Y., & Chuang, K. H. (2017). Poly-protein G-expressing bacteria enhance the sensitivity of immunoassays. Scientific reports, 7(1), [989]. https://doi.org/10.1038/s41598-017-01022-w