Dual-Shaped Silver Nanoparticle Labels for Electrochemical Detection of Bioassays

Abstract

In this paper, we demonstrate the use of dualshaped silver nanoparticles (AgNPs) as detection labels for electrochemical bioassays. The key finding is that by simultaneously using AgNP labels having two different shapes, the limit of detection (LOD) for the assays is lowered compared to using either of the two shapes separately. The two shapes were silver nanocubes (AgNCs) having edge lengths of 40 ± 4 nm and spherical AgNPs (sAgNPs) having diameters of 20 ± 3 nm. Two different bioassays were examined. In both cases, the Ag labels were functionalized with antibodies. In the first assay, the labels are directly linked to a second antibody immobilized on magnetic beads. In the second assay, the antibodies on the AgNP labels and the antibodies on the magnetic beads are linked via a peptide. The peptide is N-terminal prohormone brain natriuretic peptide (NT-proBNP), which is a heart-failure marker. The efficacy of the two electrochemical assays as a function of the ratio of the two labels was investigated using a galvanic exchange/anodic stripping voltammetry method. The key finding is that by optimizing the ratio of the two types of AgNP labels, it is possible to decrease the LOD of the assays without compromising the dynamic range compared to using either of the two labels independently. This made it possible to achieve the clinically relevant range for NT-proBNP analysis used by physicians for heart failure risk stratification.

Silver nanoparticles in electrochemical immunosensing and the emergence of silver–gold galvanic exchange detection

“…Then, the group developed several immunosensors, where a GE/ASV electrochemical method was utilized to detect different shapes of AgNP labels. 104,[115][116][117][118][119][120][121][122] It was demonstrated that the shape of the AgNP played a crucial role in determining the detection efficiency of metalloimmunoassay based on GE/ASV process. Specifically, it was shown that the LOD and analyte detection range could be tuned by simply altering the shape of the silver nanoparticle.…”

Paper Biosensor for the Detection of NT-proBNP Using Silver Nanodisks as Electrochemical Labels

“…We recently addressed this problem by using two different types of Ag labels simultaneously: spherical AgNPs and Ag nanocubes [25]. This approach was effective, because the Ag nanocubes are sensitive to the lower concentrations of NT-proBNP, while the spherical AgNPs are effective at the higher end of the risk stratification range [26]. The more general conclusion of this study was that the dynamic range of metalloimmunoassay can be tuned simply by changing the shape of the metallic labels.…”

Plastic-based lateral flow immunoassay device for electrochemical detection of NT-proBNP

“…[1][2][3] We have been developing an electrochemical metalloimmunoassay for the heart failure biomarker N-terminal prohormone brain natriuretic peptide (NT-proBNP), which is a short peptide. [4][5][6][7] The baseline concentration of NT-proBNP in the blood of a patient depends on a number of variables, including their stage of heart failure, comorbidities, age, and race. [8][9][10][11][12] Changes in the baseline level of NT-proBNP may be an indication of disease progression, and therefore there is a need for monitoring NT-proBNP levels at home.…”

“…24 These two reagents act in concert to provide a picomolar limit of detection for NT-proBNP. 4,6 Specifically, the MµBs preconcentrate the assay conjugate over a working electrode (WE), which itself is configured over a magnet. 4,25,26 The AgNPs provide a maximum amplification factor of 250 000 upon oxidation.…”

“…5,27 Following preconcentration of the immunoassay over the WE, a series of electrochemical steps (discussed later) are carried out to quantitatively detect the AgNP labels, which are correlated to the NT-proBNP concentration in the sample. 4,6 One challenge we have encountered with this approach is that the immunoconjugates attached to the MµBs become trapped in the porous matrix of the paper device, and therefore they do not properly move down the paper strip. 28,29 To solve this problem, we and others developed hollow channel paperbased devices wherein the sample flow occurs in the hollow microfluidic channel instead of the porous matrix.…”