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. 2021 Apr 28:9:631571.
doi: 10.3389/fchem.2021.631571. eCollection 2021.

A Bifunctional Nanosilver-Reduced Graphene Oxide Nanocomposite for Label-Free Electrochemical Immunosensing

Supakeit Chanarsa  1   2 , Jaroon Jakmunee  1   3 , Kontad Ounnunkad  1   3   4
Affiliations

A Bifunctional Nanosilver-Reduced Graphene Oxide Nanocomposite for Label-Free Electrochemical Immunosensing

Supakeit Chanarsa et al. Front Chem. .

Abstract

A bi-functional material based on silver nanoparticles (AgNPs)-reduced graphene oxide (rGO) composite for both electrode modification and signal generation is successfully synthesized for use in the construction of a label-free electrochemical immunosensor. An AgNPs/rGO nanocomposite is prepared by a one-pot wet chemical process. The AgNPs/rGO composite dispersion is simply cast on a screen-printed carbon electrode (SPCE) to fabricate the electrochemical immunosensor. It possesses a sufficient conductivity/electroreactivity and improves the electrode reactivity of SPCE. Moreover, the material can generate an analytical response due to the formation of immunocomplexes for detection of human immunoglobulin G (IgG), a model biomarker. Based on electrochemical stripping of AgNPs, the material reveals signal amplification without external redox molecules/probes. Under optimized conditions, the square wave voltammetric peak current is responded to the logarithm of IgG concentration in two wide linear ranges from 1 to 50 pg.ml-1 and 0.05 to 50 ng.ml-1, and the limit of detection (LOD) is estimated to be 0.86 pg.ml-1. The proposed immunosensor displays satisfactory sensitivity and selectivity. Importantly, detection of IgG in human serum using the immunosensor shows satisfactory accuracy, suggesting that the immunosensor possesses a huge potential for further development in clinical diagnosis.

Keywords: Immunoglobulin G; electrochemistry; immunosensor; reduced graphene oxide; screen-printed carbon electrode; silver nanoparticles.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Scheme 1
Scheme 1
Fabrication of AgNP/rGO-based electrochemical immunosensor.
Figure 1
Figure 1
SEM images of GO (A) and AgNPs/rGO (B) coated on SPCEs. A TEM image (C) of AgNPs/rGO and a particle size distribution profile (D) of AgNPs on rGO sheets.
Figure 2
Figure 2
CV results of bare SPCE, and GO and AgNPs/rGO-modified SPCEs in contact with PB (pH 7.4).
Figure 3
Figure 3
(A) CV curves at a scan rate of 100 mV s−1 and (B) Nyquist plots of bare SPCE, and GO- and AgNP/rGO-modified SPCEs in contact with 0.10 M PB (pH 7.4) containing 5 mM K3[Fe(CN)6]/K4[Fe(CN)6].
Figure 4
Figure 4
CVs of the AgNPs/GO-modified SPCE in contact with 0.010 M PB (pH 7.4) containing 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] at different scan rates: 10, 20, 40, 50, 80, 100, 125, 200, 250, and 400 mVs−1. Inset: plots of the anodic peak current (Ipa) and the cathodic peak current (Ipc) vs. the square root of the scan rate.
Figure 5
Figure 5
Influence of incubation time of anti-IgG (A), incubation time of IgG (B), pH of phosphate buffer (C) on current responses of the developed immunosensor.
Figure 6
Figure 6
SWVs of the immunosensor after incubation with different concentrations of IgG. Inset: a calibration curve based on the change in the SWV peak current vs. the logarithm of the concentration (n = 3).
Figure 7
Figure 7
Selectivity study of the immunosensors incubated with different solutions: blank (blue bar), IgG solution (1 ng ml−1, red bar), interference solutions (100 ng ml−1) with presence of 1 ng ml−1 IgG (red bars), and individual interference solutions (100 ng ml−1) with no IgG (blue bars).
See this image and copyright information in PMC

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