Development of a stable dual functional coating with low non-specific protein adsorption and high sensitivity for new superparamagnetic nanospheres.

To overcome major challenges of non-specific protein adsorption on nanoparticles for nanosensing and nanodiagnosis, an efficient method for robust chemical modification was developed to achieve excellent specific biorecognition and long-term stability in complex biomedia. This method is demonstrated by a highly specific and sensitive immunoassay (IA), using superparamagnetic nanospheres (NSs) with high magnetite content. The non-specific protein adsorption on the NSs was suppressed dramatically when modified with dual functional poly(carboxybetaine methacrylate) (polyCBMA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and chemically grafted with antibodies of the β subunit of human chorionic gonadotrop (anti-β-hCG). The response to hCG of IA NSs with polyCBMA coatings was highly consistent in either phosphate-buffered saline (PBS) or 50% fetal bovine serum (FBS), which is far less variable than the response of the IA NSs without polyCBMA coatings. After all, a very robust platform f...