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. 2019;9(5):2618-2625.
doi: 10.1039/C8RA09230C. Epub 2019 Jan 18.

A SERS Aptasensor for Sensitive and Selective Detection of bis(2-ethylhexyl) Phthalate

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Free PMC article

A SERS Aptasensor for Sensitive and Selective Detection of bis(2-ethylhexyl) Phthalate

Dandan Tu et al. RSC Adv. .
Free PMC article

Abstract

Bis(2-ethylhexyl) phthalate (DEHP) is an endocrine disruptor commonly present in plastic products, such as PVC tubes and water bottles. In this work, a surface enhanced Raman spectroscopy (SERS) based aptasensor was developed and utilized for rapid, easy, sensitive, and specific detection of trace DEHP. A DEHP aptamer was immobilized on magnetic particles. Raman reporter molecule conjugated silver nanoparticles were clustered and coated with silica to provide a stable SERS signal. The SERS silica particle was then functionalized with 1,2,4-benzenetricarboxylic acid 1,2-bis(2-ethylhexyl) ester to increase its affinity to the DEHP aptamer. In the presence of a sample with DEHP, the high-affinity SERS silica particle competes with the DEHP molecule to bind with the aptamer on the magnetic particle. By measuring the signal of free SERS silica particles in the supernatant after magnetic separation, the concentration of DEHP in the sample was quantitatively determined. The developed DEHP aptasensor had a detection range from 0.008 to 182 nM and a limit of detection (LOD) of 8 pM. The aptasensor also showed high selectivity when exposed to interferents with analogous structures. The aptasensor was successfully tested for the detection of DEHP spiked in tap water, bottled water, and a carbonate beverage. The developed SERS-based aptasensor provides a rapid, sensitive, and easy-to-use method for the quantitative detection of DEHP in environmental and food analysis.

Conflict of interest statement

Conflicts of interest There are no conflicts to declare.

Figures

Fig. 1
Fig. 1
Schematic diagram of the process to fabricate the DEHP modified SERS silica particles: First, DTNB was functionalized on AgNPs. Then, NaCl was introduced to form clusters of AgNPs. The AgNCs were then coated with a silica shell. Subsequently, AgNCs-SiO2 was functionalized with APTMS to create a surface with primary amines. Finally, DEHP-COOH was immobilized on the AgNCs-SiO2-NH2 by an amide bond using EDC/NHS chemistry.
Fig. 2
Fig. 2
Schematic illustration of the competitive binding assay based on aptamer modified magnetic particles and a SERS silica particle. (A) Left: the components functionalized on the magnetic particles. Right: the silica coated silver nanoclusters functionalized with DTNB and the DEHP conjugated on the silica shell. (B) Competitive assay steps to measure a DEHP sample. The inset shows the competitive binding reaction.
Fig. 3
Fig. 3
TEM image of the purified SERS silica particles (A) using a low magnification, (B) using a high magnification.
Fig. 4
Fig. 4
FTIR spectra of synthesized and modified SERS silica particles. (A) AgNCs-SiO2, (B) AgNCs-SiO2-NH2, and (C) AgNCs-SiO2-DEHP.
Fig. 5
Fig. 5
Calibration curve of DEHP functionalized SERS silica particles in PBS. SERS intensity at 1336 cm−1 with increasing concentration of the DEHP functionalized SERS silica particles. Error bar represents standard deviation (n=3).
Fig. 6
Fig. 6
Stability of the DEHP functionalized SERS silica particles. (A) SERS intensity at 1336 cm−1 of the SERS silica particles after 1 h exposure to PBS (0.1 M, PH 7.4) with 0.1 M, 0.2 M, 0.5 M, and 0.7 M NaCl. (B) SERS spectra of Ag nanoparticles after 1 h exposure to 0.5 mM 4-MBA, and SERS silica particles after no exposure and exposure to 0.5 mM 4-MBA.
Fig. 7
Fig. 7
(A)Response of the aptasensor to different concentrations of DEHP in 0.1 M PH 7.4 PBS. (B) Average of SERS peak intensity at ~1336 cm−1 as a function of DEHP concentration. Error bar represents standard deviation (n=3).
Fig. 8
Fig. 8
Selectivity test of the DEHP aptasensor. The SERS signal was measured after testing a blank sample and 100 nM of DEHP, DBP, BBP, DINP, DIDP, DEP, DMP, and TOTM respectively. Error bar represents standard deviation (n=3).

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