A promising direct visualization of an Au@Ag nanorod-based colorimetric sensor for trace detection of alpha-fetoprotein

Abstract

The Ag coating-induced blue shift and enhancement of longitudinal plasmon of Au nanorods result in abundant and tunable optical absorptions in the visible region, which leads to the Au@Ag nanorod becoming a good candidate for colorimetric sensing. In this paper, we have reported an effective and simple approach for visualization detection of alpha-fetoprotein (AFP) based on Au@Ag core-shell nanorods. The AFP concentration-dependent colloid color of Au@Ag core-shell nanorods could change from green to gray, olivine to brown, and even blue to violet to pink, which are more varied color changes compared with the traditional red to blue color change. Besides, as the Ag shell thickness is increased, a dip was observed, which is located between two strong absorption peaks. The change of the dip is proposed as a new biosensor parameter for biomolecule detection based on absorption spectra.AFP concentration detection could be realized according to the change of the position and intensity of the dip, which has not been reported in the biomolecule detection field so far. Au@Ag core-shell nanorods with a small aspect ratio of inner Au nanorods are more suitable for direct read-out visualization, with a color change from blue to violet to pink. From the point of view of spectra analysis, Au@Ag core-shell nanorods with a greater aspect ratio of inner Au nanorods show higher spectral sensitivity. Furthermore, it is found that non-centrifuged Au@Ag core-shell nanorods are preferentially assembled in a side-by-side fashion with the addition of AFP, which will provide new approaches for other kinds of nanorods in controllable assembly fashions.

Bimetallic Nanoparticles: Enhanced Magnetic and Optical Properties for Emerging Biological Applications

“…Specifically, certain biological molecules such as peptide nucleic acids (PNA), DNA aptamers, and protein antigens, can induce nanoparticle aggregation; a shift in the extinction peaks of the nanoparticles will then indicate the presence of the targeted molecules [161,162]. For example, Fan Zhang et al used Au@Ag nanorods for the colorimetric sensing of the biological molecule alpha-fetoprotein, a biomarker for hepatocellular carcinoma in human serum [163].…”

“…Sensing LSPR shift AuAg [163] Surface-enhanced Raman scattering (SERS) AuAg [76] AuAg [166] GMR sensor; competition assay FeCo [112,113,187] Magnetic capture FePt [171] Magnetically-enhanced colorimetric biosensing PtCo [117] QCM with magnetically controlled permeability AuCo [80] Electrochemical biosensor PtPd [96] Imaging An imaging probe screening with dual energy mammography or computed tomography AuAg [71] The optical absorption cross sections AuAg [72] MRI contrast agent (no imaging) FePt [103] MRI in vitro FePt [105] FeNi [115] PtCo [40] MRI in vivo AuCu [84] FeCo [110] FePt [177] Dual modal CT/MRI molecular imaging in vitro and in vivo FePt [132] MRI and near-infrared agents FeCo [111] Multimodal imaging − Computed tomography (CT), − Magnetic resonance imaging (MRI), − Photoacoustic (PA) imaging, − High-order multiphoton luminescence (HOMPL) microscopy FePt [102] in vivo Multimodal SERS-MRI-CT imaging AuFe [79] in vivo NIR thermal imaging and photoacoustic imaging AuPt [95] Thermal treatment in vitro hyperthermia FePt [109] Photothermal FePt [104] Hyperthermia CuNi [119,188] Tumor chemo-photothermal therapy AuPt [95]…”

Highly sensitive and selective visual detection of Cr(VI) ions based on etching of silver-coated gold nanorods

“…Real samples were also tested to confirm the practicability and the results proved that our sensor has good performance in terms of selectivity, sensitivity, linearity, and low limit of detection. This is due to the high extinction coefficient of AuNR@Ag and the signal amplification effect of Ag nanoshells [44–46]. The longitudinal plasmon resonance of AuNR@Ag was blue-shifted as the deposited Ag nanoshells becomes thicker, which could be lead to apparent multicolor change.…”

Bimetallic Nanoparticles: Enhanced Magnetic and Optical Properties for Emerging Biological Applications

“…Specifically, certain biological molecules such as peptide nucleic acids (PNA), DNA aptamers, and protein antigens, have the ability to induce nanoparticle aggregation; a shift in the extinction peaks of the nanoparticles will then indicate the presence of the targeted molecules [129,130]. For example, , Fan Zhang et al used Au@Ag nanorods for the colorimetric sensing of the biological molecule alpha-fetoprotein, a biomarker for hepatocellular carcinoma in human serum [131].…”