Multiple antibody conjugation to PEG grafted copolymer improves sensitivity of immunoassays

A polyethylene glycol (PEG) grafted copolymer based on a N-vinyl pyrrolidone (NVP) backbone was designed for conjugating antibodies (Abs) at PEG chain ends, leading to multivalent (multi-antibody) bioconjugate for use as a detection system in immunoassays. For this purpose, a poly(N-vinyl pyrrolidone-co-N-acryloxysuccinimide) (P(NVP-co-NAS)) copolymer was prepared by nitroxide mediated polymerization (NMP) and the N-succinimidyl activated esters of the NAS units were used for grafting heterobifunctional amine-PEG-maleimide by amidation. The PEG maleimide end-groups were further conjugated to Abs through thiol-maleimide addition. Enzyme-linked immunosorbent assay (ELISA) performed with the obtained bioconjugate in the detection phase showed significant improvement in antigen detection as compared to standard protocol with free Ab. These results point out the relevance of this straightforward approach to improve antibody accessibility and reduce background noise (thanks to anti-fouling PEG) for enhanced sensitivity in the field of immunoassays. © 2024 Elsevier Ltd