Zwitterionic reagents for labeling, cross-linking and improving the performance of chemiluminescent immunoassaysElectronic supplementary information (ESI) available. See DOI: 10.1039/c2ob06807a

• Main Authors: Natrajan, Anand, Sharpe, David, Wen, David
• Format: Journal Article
• Language: English
• Published: 09.02.2012
• DOI: 10.1039/c2ob06807a
• ISSN: 1477-0520

Improving reagent performance in immunoassays both to enhance assay sensitivity and to minimize interference are ongoing challenges in clinical diagnostics. We describe herein the syntheses of a new class of hydrophilic reagents containing sulfobetaine zwitterions and their applications. These zwitterionic reagents are potentially useful for improving the properties of immunoassay reagents. We demonstrate for the first time that zwitterion labeling is a general and viable strategy for reducing the non-specific binding of proteins to microparticles and, to improve the aqueous solubility of hydrophobic peptides. We also describe the synthesis of zwitterionic cross-linking reagents and demonstrate their utility for peptide conjugation. In automated, chemiluminescent immunoassays, improved assay performance was observed for a hydrophobic, small analyte (theophylline) using an acridinium ester conjugate with a zwitterionic sulfobetaine linker compared to a hexa(ethylene)glycol linker. Sandwich assay performance for a large analyte (thyroid stimulating hormone) was similar for the two acridinium ester labels. These results indicate that zwitterions are complementary to poly(ethylene)glycol in improving the aqueous solubility and reducing the non-specific binding of chemiluminescent acridinium ester conjugates. Reactive zwitterionic reagents improve the solubility of hydrophobic antigens, reduce the non-specific binding of proteins and improve chemiluminescent immunoassay performance.