Ethanol and NaCl-Induced Gold Nanoparticle Aggregation Toxicity toward DNA Investigated with a DNA/GCE Biosensor

Abstract

Engineered nanomaterials are becoming increasingly common in commercial and consumer products and pose a serious toxicological threat. Exposure of human organisms to nanomaterials can occur by inhalation, oral intake, or dermal transport. Together with the consumption of alcohol in the physiological environment of the body containing NaCl, this has raised concerns about the potentially harmful effects of ingested nanomaterials on human health. Although gold nanoparticles (AuNPs) exhibit great potential for various biomedical applications, there is some inconsistency in the case of the unambiguous genotoxicity of AuNPs due to differences in their shape, size, solubility, and exposure time. A DNA/GCE (DNA/glassy carbon electrode) biosensor was used to study ethanol (EtOH) and NaCl-induced gold nanoparticle aggregation genotoxicity under UV light in this study. The genotoxic effect of dispersed and aggregated negatively charged gold nanoparticles AuNP1 (8 nm) and AuNP2 (30 nm) toward salmon sperm double-stranded dsDNA was monitored by cyclic and square-wave voltammetry (CV, SWV). Electrochemical impedance spectroscopy (EIS) was used for a surface study of the biosensor. The aggregation of AuNPs was monitored by UV-vis spectroscopy. AuNP1 aggregates formed by 30% v/v EtOH and 0.15 mol·L^-1 NaCl caused the greatest damage to the biosensor DNA layer.

Keywords: DNA/GCE biosensor; NaCl; aggregation; ethanol; gold nanoparticles; toxicity.

Figure 1

UV-vis spectra of AuNP1 (A–D) and AuNP2 (E,F). The absorbance of the dispersed form is shown in panels (A) (AuNP1) and (E) (AuNP2). AuNP1 in the presence of 0.15 mol·L⁻¹ NaCl and 30% v/v EtOH (B), 40% v/v EtOH (C), or 50% v/v EtOH (D) show differences in UV-vis spectra due to their aggregation. Similar differences in absorbance are observed within AuNP2 in the presence of 0.15 mol·L⁻¹ NaCl and 30% v/v EtOH (F), 40% v/v EtOH (G), or 50% v/v EtOH (H).

Figure 2

The response of the DNA/GCE biosensor to dispersed AuNP1 was measured by CV (A), SWV (C), and EIS (B) after the 20 s (orange curve), 60 s (blue curve), 300 s (gray curve), 600 s (purple curve), and 900 s (green curve) of UV irradiation. The black color represents the signal of the bare GCE, and the red color represents the response of the DNA/GCE in the presence of AuNP1. CV and EIS show the response of the [Fe(CN)₆]^3−/4− redox indicator, and SWV shows the measured current response for guanine and adenine DNA moieties.

Figure 3

The response of the DNA/GCE biosensor to dispersed AuNP2 was measured by CV (A), SWV (C), and EIS (B) after the 20 s (orange curve), 60 s (blue curve), 300 s (gray curve), 600 s (purple curve), and 900 s (green curve) of UV irradiation. The black color represents the signal of the bare GCE, and the red color represents the response of the DNA/GCE in the presence of AuNP2. CV and EIS show the response of the [Fe(CN)₆]^3−/4− redox indicator, and SWV shows the measured current response for guanine and adenine DNA moieties.

Figure 4

Amount of surviving DNA calculated based on normalized CV responses after treatment of the DNA/GCE with AuNP1 and AuNP2 alone (A); after treatment of the DNA/GCE in the presence of 0.15 mol·L⁻¹ NaCl and 30%, 40%, or 50% v/v EtOH (B); after treatment of the DNA/GCE in the presence of AuNP1 and 0.15 mol·L⁻¹ NaCl and 30%, 40%, or 50% v/v EtOH (C); and after treatment of the DNA/GCE in the presence of AuNP2 and 0.15 mol·L⁻¹ NaCl and 30%, 40%, or 50% v/v EtOH (D) under UV irradiation for 0, 20, 60, 300, 600, and 900 s.

Figure 5

SWV responses of AuNP1 and AuNP2 impact on DNA on the DNA/GCE biosensor in the presence of 0.15 mol·L⁻¹ NaCl and 30%, 40%, or 50% v/v EtOH after 0 s (red curve), 20 s (orange curve), 60 s (blue curve), 300 s (gray curve), and 900 s (green curve) of UV irradiation. The ↑ arrows represent opening of the DNA structure and the ↓ arrows represent DNA damage. The Nyquist plots show the response of the [Fe(CN)₆]^3−/4− redox indicator on the DNA/GCE biosensor under the same experimental conditions. The black curve represents the response of bare GCE and the dark blue curve represents the response after 600 s of UV irradiation.