Functionalization of gold nanorod‐based immunosensors for label‐free bio‐detection with high sensitivity and specificity (780.7)

Abstract

Gold nanoparticles have shown great potential applications in biomedical diagnosis and therapeutic treatments due to their shape and size‐dependent optical properties. However, densely packed CTAB double layer (surfactant used to prevent nanoparticle aggregation) on the nanorod surfaces present challenges for effective biofunctionalization to setup a nanoparticle‐based platform with high detection sensitivity. In this study, we systematically studied the functionalization of gold nanorods (GNRs) with various bioconjugate linkers in pursuit of developing nanorod‐based immunosensors with maximal sensitivity and specificity. First, GNR chips were fabricated by chemically binding nanorods onto silanized glass substrate; then the GNRs were functionalized with carboxylic acid or amine group via thiol linkers for antibody conjugation. The effects of thiol linkers with different lengths such as 11‐mercaptoundecanic acid (MUDA), 4‐aminothiophenol (4‐ATP), 2‐mercaptopropionic acid (MPA), cysteamine hydrochloride (CAE) and 6‐mercaptohexanoic acid (MHA) were investigated. GNR nano‐biochip exhibited high detection sensitivity (0.3017/ IgGnM), low detection limit (1.3 nM) and high specificity, with the features of label free and simple detection mechanism. The optimized functionalization of GNR chip was applied to develop a nano‐biosensor to detect human serum IgG as a model system. Since the localized surface plasmon resonance is highly sensitive to the biological binding on the nanorod surface, this mechanism provides a label‐free biodetection, eliminating signaling labels such as fluorophore and radioactive agents. The miniaturized nano‐biochip is attractive for rapid medical diagnostics in clinics, due to its user‐friendly and cost‐effective features.