Gold nanoparticle-catalyzed uranine reduction for signal amplification in fluorescent assays for melamine and aflatoxin B1

Abstract

A multifunctional fluorescence platform has been constructed based on gold nanoparticle (AuNP)-catalyzed uranine reduction. The catalytic reduction of uranine was conducted in aqueous solution using AuNPs as nanocatalyst and sodium borohydride as reducing reagent, which was monitored by fluorescence and UV-vis spectroscopy. The reaction rate was highly dependent on the concentration, size and dispersion state of AuNPs. When AuNPs aggregated, their catalytic ability decreased, and thereby a label-free fluorescent assay was developed for the detection of melamine, which can be used for melamine determination in milk. In addition, a fluorescent immunoassay for aflatoxin B1 (AFB1) was established using the catalytic reaction for signal amplification based on target-induced concentration change of AuNPs, where AFB1-BSA-coated magnetic beads and anti-AFB1 antibody-conjugated AuNPs were employed as capture and signal probe, respectively. The detection can be accomplished in 1 h and acceptable recoveries in spiked maize samples were achieved. The developed fluorescence system is simple, sensitive and specific, which could be used for the detection of a wide range of analytes.

Optical Nanoprobes for Ultrasensitive Immunoassay

“…Knopp's group also designed a magnetic bead-based fluorescent immunoassay for AFB1 using AuNP-catalyzed uranine reduction for signal amplification. 46 Due to the high catalytic activity of AuNP toward uranine, the developed fluorescence system exhibited a high sensitivity for AFB1 with a detection limit of 17.1 pg mL −1…”

The role of OH−in the formation of highly selective gold nanowires at extreme pH: multi-fold enhancement in the rate of the catalytic reduction reaction by gold nanowires

“…Therefore, once the total amount of gold present in the solution reacts with the sodium borohydride, 4-aminophenol will be formed. 38,40,60,61 However, in the presence of Au nanocatalyst, the complete reduction of 4-nitrophenolate to 4-aminophenol by NaBH 4 was observed within a few minutes, B4 minutes maximum, (Fig. 12B) revealing that the resultant Au nanocatalyst indeed possessed excellent catalytic activity for the reduction of 4-nitrophenol.…”

“…The present work could serve the purpose of gaining a better understanding on how different parameters affect the formation of gold nanowires and their potential application in catalysis of the reduction of nitro-aromatics, since the reduction of organic compounds like 4-nitrophenol has been used for the detection of different proteins; however, this catalytic reduction is only limited to several colored substances, including methyl orange, 4-nitrophenol and methylene blue. [36][37][38][39][40] In our earlier work, 20 we reported that curcumin could help in the formation of Au nanorods through pre-reduction and it enhances Au nanorod formation prepared from CTAB capped over citrate capped Au seeds. In the available literature, the role of OH À in dictating the size and shape of Au nanowires is unknown.…”

Review on Nanomaterial-Based Melamine Detection

“…This method was also legalised as an effective procedure for melamine detection, but still much focus is required to improve its applicability and detection limits. Subsequently, the catalytic property of antibody conjugated Au NPs was exploited towards melamine determination by Knopp's group [150]. Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) was engaged in the quantification of melamine in infant formula and grain powder by Hsieh and co-workers [164].…”