Gold Nanorods as Colorful Chromogenic Substrates for Semiquantitative Detection of Nucleic Acids, Proteins, and Small Molecules with the Naked Eye

Abstract

Herein, we report for the first time a colorful chromogenic substrate, which displays vivid color responses in the presence of different concentration of analytes. Our investigation reveals that the selective shortening of gold nanorods (AuNRs) could generate a series of distinct colors that covers nearly the whole visible range from 400 to 760 nm. These vivid colors can be easily distinguished by the naked eye; as a result, the accuracy of visual inspection could be greatly improved. Next, we demonstrate the utility of AuNRs as multicolor chromogenic substrate to develop a number of colorimetric immunoassay methods, e.g., multicolor enzyme-linked immunosorbent assay (ELISA), multicolor competitive ELISA, and multicolor magnetic immunoassay (MIA). These methods allow us to visually quantify the concentration of a broad range of target molecules with the naked eye, and the obtained results are highly consistent with those state-of-the-art techniques that are tested by the sophisticated apparatus. These multicolor portable and cost-effective immunoassay approaches could be potentially useful for a number of applications, for example, in-home personal healthcare, on-site environmental monitoring, and food inspection in the field.

Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles: Strategies and applications

“…To date, different metal nanoparticles, such as gold nanospheres, gold nanorods, silver nanospheres, silver nanoprisms, core/shell Au@Ag nanospheres, and core/shell Au@Ag nanorods, have been used as etching-based plasmonic sensors. Etching-based plasmonic sensors incorporating these nanoparticles have been used to detect various targets including DNA, (Ma et al, 2016;Malile and Chen, 2013;Yang et al, 2014) proteins, (Cheng et al, 2016;Guo et al, 2016b;Liang et al, 2015a;Lu et al, 2016;Yang et al, 2017;Zhang et al, 2015b;Zhao et al, 2016) metal ions, (Chang et al, 2017;Chemnasiri and Hernandez, 2012;Chen et al, 2016bChen et al, , 2016cChen et al, , 2009Chen et al, , 2013bJin and Han, 2014;Lan and Lin, 2014;Liu et al, 2013c;Wang et al, 2014;Yao et al, 2017;Zhang et al, 2014aZhang et al, , 2014bZhu et al, 2016) anions, (Chen et al, 2015(Chen et al, , 2012bHe and Yu, 2015;Li et al, 2011Li et al, , 2015Liu et al, 2013a;Sasikumar and Ilanchelian, 2017;Tripathy et al, 2011;Xin et al, 2012;Zeng et al, 2014;Zhang et al, 2015aZhang et al, , 2016 and glucose, (Jang and Min, 2015;Lin et al, 2016;…”

Nanomaterials-Based Colorimetric Immunoassays

“…Some oxidants (such as I 2 [144], H 2 O 2 [145], TMB 2+ [15], Cu 2+ [146]) or reactions (such as the Fenton reaction) [147] can cause the oxidization of Au/Ag into Au(I)/Ag(I) in certain situations and thus lead to a change of the shape of anisotropic NPs to a sphere with a blue-shift of the LSPR absorption. By iodine-mediated etching of AuNRs, Chen’s group proposed a plasmonic ELISA for the sensitive quantification of human IgG in fetal bovine serum (Figure 13B) [144].…”

“…Tang’s group reported a plasmonic ELISA for the quantitative assessment of PSA based on antibody-labeled GOx-catalysed oxidation of glucose (Glu) to produce H 2 O 2 and the triangular Ag nanoprism [145]. Guo’s group suggested that Fenton’s reaction can promote the oxidation of AuNRs by H 2 O 2 and reported the vivid color display of AuNRs with various types of immunoassays for the visual detection of different targets with the naked eye (Figure 13C) [147]. Lin’s group first demonstrated that TMB 2+ , a typical HRP-catalyzed colorimetric product, can quantitatively and efficiently etch AuNRs.…”

A colorimetric sensing platform based on self-assembled 3D porous CeGONR nanozymes for label-free visual detection of organophosphate pesticides

“…21,22 For example, MnO 2 , Co 3 O 4 NPs, and Cu NCs are inactivated after solvent exposure or contact with acidic, reducing substances; Au nanorods and gold/silver core/shell nanorods are etched easily by H 2 O 2 and protonated TMB (TMB 2+ ). 23,24 To overcome these disadvantages, the reported approaches of doping elements, changing morphology or decreasing the size of NPs could partially improve the catalytic activity. 25 However, these methods either involve complex synthetic processes or there are problems of aggregation, which lead to inadequate extents of process control and compromised enzymatic activity.…”