Trace analysis of mercury(ii) ions using aptamer-modified Au/Ag core–shell nanoparticles and SERS spectroscopy in a microdroplet channel

Abstract

We report the rapid and highly sensitive trace analysis of mercury(ii) ions in water using a surface-enhanced Raman scattering (SERS)-based microdroplet sensor. Aptamer-modified Au/Ag core-shell nanoparticles have been fabricated and utilized as highly functional sensing probes. All detection processes for the reaction between mercury(II) ions and aptamer-modified nanoparticles were performed in a specially designed microdroplet channel. Small water droplets that included sample reagents were separated from each other by an oil phase that continuously flowed along the channel. This two-phase liquid-liquid segmented flow system prevented the adsorption of aggregated colloids to the channel walls due to localized reagents within encapsulated droplets. The result was reduced residence time distributions. The limit of detection (LOD) of mercury(II) ions in water was determined by the SERS-based microdroplet sensor to be below 10 pM, which is three orders below the EPA-defined maximum contaminant level. This combination of a SERS-based microfluidic sensor with aptamer-based functional nanoprobes can be used for in-the-field sensing platforms, due to its size and simplicity.

An electrochemical aptasensor for thrombin using synergetic catalysis of enzyme and porous Au@Pd core–shell nanostructures for signal amplification

“…Particularly, noble metal-based nanoparticles, such as gold nanoparticles (AuNPs) with large specific surface area and excellent biocompatibility (Wen et al, 2014), Palladium nanoparticles (PdNPs) that possess excellent electrocatalytic performance (Qi et al, 2014), have been extensively used in the construction of biosensors (Wang et al, 2014a;Xia et al, 2013;Lan et al, 2014). Recently, as the result of the enhanced physical, chemical, and prominent catalytic properties over the corresponding monometallic components (He et al, 2012;Ferrer et al, 2007), bimetallic nanoparticles with core-shell structures have aroused much attention in various of biosensors (Gui and Jin, 2013;Miao et al, 2014;Chung et al, 2013). Besides, porous nanomaterials have also received particular interest in biosensing field due to their large specific surface area, numerous catalytic hot spots and high-index exposed facets (Wang et al, 2013a;Zhu et al, 2010).…”

Utilisation of micro- and nanoscaled materials in microfluidic analytical devices

“…Chung et al [95] also developed a sensitive method for trace analysis of Hg(II) ions in water using a surface enhanced Raman scattering (SERS)-based microdroplet sensor. Aptamer-modified Au/Ag coreshell nanoparticles were used as sensing probes in the microdroplet channel.…”

Review—Surface-Enhanced Raman Scattering Sensors for Food Safety and Environmental Monitoring

“…Figure 16b shows a droplet microfluidic device for detection of Hg 2+ ions in water, achieving a LOD of 10 pM. 172 The aptamer-linked SERS probes were immobilized on the surface of Au-Ag core-shell NPs via hybridization of a complementary DNA covalently linked to the NP. Small water droplets containing the Hg 2+ ions were separated from each other by an oil phase, which flowed along the microfluidic channel.…”

“…In contrast, the segmented flow microfluidic devices avoid mixing between two miscible liquid streams by introducing a gas phase or oil phase. 172,259,260 The segmented flow platforms can separate the continuous sample flow and colloidal nanoparticles by droplets of an immiscible fluid phase. The memory effect can be reduced because the droplets avoid significant liquid exchange between the liquid segments.…”

“…Another typical example is shown in Figure 8b. 172 At the initial state, a plasmonic gold nanostructure was functionalized with Aptamer 1, being paired with a complementary Aptamer 2 with one end linked with a SERS probe. The SERS probe was close to the gold nanostructure initially, showing strong SERS signal.…”