Gold Nanoclusters as Signal Amplification Labels for Optical Immunosensors

A portable, low-cost optical immunosensor has been developed using environment-friendly gold nanoclusters (AuNCs) as signal amplification labels. The stable and robust film, poly(dopamine), was used to immobilize biomolecules on an indium tin oxide chip for the construction of biosensor, as confirmed by scanning electron microscopy, contact angle, and electrochemical impedance spectroscopy. Human IgG served as a model to demonstrate the performance of the proposed sensor. Through sandwiched immunoreaction, IgG could be qualitatively and quantitatively determined by colorimetry, fluorescence method, as well as eye observation according to the clinical requirement. On the basis of the dual signal amplification of AuNCs and silver enhancement, the sensitivity was improved to 5 pg/mL. Moreover, the resulting immunosensor possessed portability, high precision, excellent stability, and reproducibility, which could be used in the clinical analysis.