Reversion of gold nanoparticle aggregates for the detection of Cu²⁺and its application in immunoassays

Abstract

A high concentration of copper is a hazardous element to organisms and human health. Although various strategies have been reported for the sensitive detection of copper, a facile and rapid detection of aqueous copper has seldom been addressed to date. Here, we present an easy and accessible colorimetric method to detect Cu using the redispersion of cysteamine-modified gold nanoparticles (CA-AuNPs). Initially, CA caused the aggregation of AuNPs due to the electrostatic interaction and aggregated AuNPs can be regenerated in basic medium. The subsequent addition of Cu to the CA-AuNP dispersion could effectively trigger the aggregation of CA-AuNPs, resulting from the coordination reactivity between the deprotonated CA and Cu. This strategy resulted in a detection limit (LOD) of 1.52 μM in drinking water, which is below the U.S. Environmental Protection Agency permissible limit (20 μM). To demonstrate the broad application of CA-AuNPs, we further applied this method to plasmonic immunoassays based on the competitive interaction of Cu between CA-AuNPs and enzymes. The LOD of the Down syndrome biomarker hyperglycosylated human chorionic gonadotropin (H-hCG) was 0.125 mIU mL, which is better than that of commercial immunoassays. Importantly, the determination of H-hCG in serum indicates its applicability for the measurement of real samples. Our assay agrees well with the current immunoassay systems and thus it can easily be expanded to a more common sensing platform for different types of biotargets by changing the corresponding antibodies.

Gold Nanoparticle-Based Colorimetric Strategies for Chemical and Biological Sensing Applications

“…The aggregation of AuNPs results in a large red-shift of the LSPR peak, accompanied by a characteristic color change from red to blue [24]. Therefore, aggregation-based colorimetric assays have wide-ranging sensing applications in proteins [25], small molecules [26], inorganic ions [27,28], enzyme activities [29], and oligonucleotides [30]. Currently, these colorimetric assays can be divided into two systems: labeled and label-free.…”

Multifunctional one-droplet microfluidic chemosensing of ractopamine in real samples: a user-oriented flexible nano-architecture for on-site food and pharmaceutical analysis using optical sensors

“…30 The designed AuNP-based optical sensors can fall into four categories, namely aggregation–disaggregation, 31 etching, 32 growth, 33 and nanozyme-based methods. 34 The colorimetric analysis methods based on AuNP aggregation–disaggregation which causes blue-to-red or red-to-blue color shift have been widely used in small molecules, 31,35 inorganic ions, 36,37 oligonucleotides, 38 protein 39 detections as well as enzyme activity determination. 40…”

Enhancement of the Peroxidase-Like Activity of Iodine-Capped Gold Nanoparticles for the Colorimetric Detection of Biothiols

“…Among nanomaterial-based colorimetric strategies, gold nanoparticles (AuNPs) are of great interest due to their unique physical and chemical properties [22]. AuNPs are known to be stabilized by electrostatic repulsion; aggregation-based AuNP colorimetric assays are widely used for the detection of protein [23][24][25], small molecule [26][27][28], and nucleic acid targets [29,30]. Moreover, such colorimetric assays are simply adaptable to a smartphone-based device without the use of costly instruments [31,32].…”