Protein G-liposomal nanovesicles as universal reagents for immunoassays |
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Authors: | Chen Chien-Sheng Baeumner Antje J Durst Richard A |
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Institution: | a Department of Food Science & Technology, Cornell University, Geneva, NY 14456, USA b Department of Biological & Environmental Engineering, Cornell University, Ithaca, NY 14853, USA |
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Abstract: | To improve the antigen-binding activity of liposome-coupled antibodies and to develop universal liposomal nanovesicles for immunoassays, protein G was conjugated to dye-loaded liposomal nanovesicles for the preparation of immunoliposomes. Sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC), a heterobifunctional cross-linker, was used to modify protein G for conjugation to the liposomal nanovesicles. Liposome immunosorbent assays were used to evaluate the binding ability of protein G after sulfo-SMCC modification, to optimize the protein G density on the liposome surface and to determine the amount of IgG binding to the protein G-liposomal nanovesicles. Test strips coated with a narrow zone of antibodies were used to show the successful conjugation. Immunomagnetic beads were used to demonstrate the feasibility of protein G-tagged universal liposomal nanovesicles for immunoassays. Results indicate that the Fc-binding capacity of protein G decreased by only 5.3% after sulfo-SMCC modification. Antibodies were easily conjugated to universal protein G-liposomal nanovesicles in 30 min. The conjugates (protein G-immunoliposomes) were successfully used in immunomagnetic bead assays for the detection of Escherichia coli O157:H7 with a detection limit of approximately 100 CFU/ml. This work demonstrated that protein G-liposomal nanovesicles are a successful universal reagent for easily coupling antibodies in an active orientation on the liposome surface for use in immunoassays. |
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Keywords: | Protein G Liposome Nanovesicle Universal reagent Immunoassay |
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