Propargylated cello-oligosaccharide nanosheets: a water-dispersible, antibiofouling, and post-functionalizable solid support for immunoassays

Immunoassays of antibodies are crucial for infection and disease diagnosis, therapeutic drug monitoring, and other purposes. For enhancing immunoassay reliability, the development of efficient solid supports is important. In this study, we propose water-dispersible, antibiofouling, and post-functionalizable cello-oligosaccharide nanosheets as a solid support for enzyme-linked immunosorbent assay (ELISA) immunoassays of anti-poly(ethylene glycol) (PEG) antibodies. A series of nanosheets exposing oligo(ethylene glycol) (OEG) chains of varying chain lengths and conjugation rates were synthesized in two steps: an enzyme-catalyzed oligomerization reaction for the synthesis of propargylated cello-oligosaccharide nanosheets and a subsequent click reaction for the conjugation of OEGs. The antibiofouling properties of the propargylated cello-oligosaccharide nanosheets allowed detergent-free ELISAs of two monoclonal anti-PEG antibodies, providing results consistent with their reported binding specificities. Moreover, remarkable results were obtained for another antibody (clone 15-2b); 15-2b antibody bound to an OEG chain with a terminal methoxy group and additional repeating EG units of 7. This binding of 15-2b was inconsistent with the previously accepted binding specificity. Additionally, quantification of anti-PEG antibodies was successfully performed, even in the presence of serum. This study highlights the significant potential of water-dispersible, antibiofouling, and post-functionalizable cello-oligosaccharide nanosheets as a solid support for ELISA immunoassay of antibodies.