Highly Sensitive and Selective Surface-Enhanced Raman Spectroscopy Label-free Detection of 3,3′,4,4′-Tetrachlorobiphenyl Using DNA Aptamer-Modified Ag-Nanorod Arrays

Abstract

An improved label-free approach for highly sensitive and selective detection of 3,3',4,4'-tetrachlorobiphenyl (PCB-77), a type of polychlorinated biphenyl, via surface-enhanced Raman spectroscopy (SERS) using DNA aptamer-modified Ag-nanorod arrays as the effective substrate is reported. The devised system consists of Ag-nanorod (Ag-NR) arrays with the PCB-77 binding aptamers anchored covalently to the Ag surfaces through a thiol linker. The aptamers are made of single-stranded DNA (ssDNA) oligomers, with one end standing on the Ag surface, and upon conjugation with PCB-77, the ssDNA molecules can change their conformation to hairpin loops, so that the Raman intensity of guanines at the other end of the DNA strand increases accordingly. As such, the intensity ratio I(656 cm(-1))/I(733 cm(-1)) increases concomitantly with the increase of the concentration of PCB-77, making the quantitative evaluation of trace amounts of PCB-77 attainable. Moreover, it is found that the DNA aptamer-based Ag-NR arrays can be more responsive with a lower and optimal density of the DNA molecules modified on the substrate surface, and the best sensitivity for detection of PCB-77 can be achieved with the lower detection limit approaching 3.3 × 10(-8) M. This work therefore demonstrates that the design of aptamer-modified Ag-NRs can be used as a practically promising SERS substrate for label-free trace detection of persistent organic pollutants (POPs) in the environment.

Structural and vibrational studies of equilenin, equilin and estrone steroids

“…Steroid hormones are important compounds found in the human body that are derived from cholesterol and have characteristics lipid-soluble and normally are grouped into two classes: corticosteroids and sex steroids differenced by bonding receptors and biological functions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Hence, different factors (solubilization, motility, transport, metabolism, and complementarity of fit between hormone and receptor) have influence on the activity of steroid hormones.…”

“…For instance, estrone, estradiol, estriol, equilenin, equilin and their derivatives are some of species associated with estrogens and, obviously, to steroid hormones [1][2][3][4][5][6][7][8][9]11,13]. Structural studies on these hormones and their quick identifications are very important from medicinal, chemistry, human health, environmental and pharmacological points of view because when these hormones are discharged toward the environmental can affect the systems of all living beings [14,15]. On the other hand, from long time the vibrational spectroscopy was a very useful technique used widely to detect the species related to steroid hormones, as evidenced in the numerous research papers published in the literature [10,12,14,17].…”

“…Structural studies on these hormones and their quick identifications are very important from medicinal, chemistry, human health, environmental and pharmacological points of view because when these hormones are discharged toward the environmental can affect the systems of all living beings [14,15]. On the other hand, from long time the vibrational spectroscopy was a very useful technique used widely to detect the species related to steroid hormones, as evidenced in the numerous research papers published in the literature [10,12,14,17]. Hence, the knowledge of their structures is necessary to perform the complete and reliable vibrational assignments of these species.…”

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

“…As a result, the intensity ratio of bands 656 cm −1 and 733 cm −1 in the aptamer changed with variation of the PCB77 concentration, enabling quantitative measurement of 1 μM PCB77. 222,223 In addition, Wu et al have developed an aptamer-based SERS sensor for detection of adenosine triphosphate (ATP). 224 The SERS probe-linked DNA was covalently bound to the Au chip (Figure 13c), in which the SERS probes (the sandwiched Au nanostar@MGITC@SiO 2 NPs) were brought in proximity with the Au chip.…”

Spectral Phasor Analysis on Nanosecond-Gated Autofluorescence Reveals Real Time Information on Cellular NAD(P)H Conformation during Chemically-Induced Metabolic Response

“…Therefore, our group combined SERS experiments with other methods such as density functional theory computation to analyze conformations and adsorptions of small biomolecules such as tyrosine [1], adenine [2] and cysteine [3], as well as the larger biomolecules such as some sequences of DNA molecules as they are attached to the metal surfaces and interact with other molecules (e.g. coralyne and PCB-77) [4][5][6] and ions (e.g. Hg 2þ ) [7].…”