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. 2020 Jan 21;5(4):1927-1937.
doi: 10.1021/acsomega.9b03655. eCollection 2020 Feb 4.

Lysine-Functionalized Tungsten Disulfide Quantum Dots as Artificial Enzyme Mimics for Oxidative Stress Biomarker Sensing

Mayank Garg  1   2 , Neelam Vishwakarma  1 , Amit L Sharma  1   2 , Boris Mizaikoff  3 , Suman Singh  1   2
Affiliations

Lysine-Functionalized Tungsten Disulfide Quantum Dots as Artificial Enzyme Mimics for Oxidative Stress Biomarker Sensing

Mayank Garg et al. ACS Omega. .

Abstract

The color generating from the biochemical reaction between 3,3',5,5'-tetramethylbenzidine and Lysine@WS2 QDs was used a signal for the detection of hydrogen peroxide. The QDs were prepared using a combination of techniques, that is, probe sonication and hydrothermal treatment. Analysis via UV-vis spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, energy-dispersive spectroscopy, and transmission electron microscopy yielded detailed information on the nature and characteristics of these quantum dots. Furthermore, as-synthesized quantum dots were studied for their capability to mimic peroxidase enzyme using 3,3',5,5'-tetramethylbenzidine as a substrate. Consequently, a colorimetric sensor utilizing Lysine@WS2 QDs could detect hydrogen peroxide in a range of 0.1-60 μM with a response time of 5 min. The same material was used for H2O2 detection using impedance spectroscopy, which yielded a dynamic range of 0.1-350 μM with a response time of 30-40 s.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) Energy-dispersive spectroscopy indicating the presence of relevant elements including carbon, oxygen, nitrogen, tungsten, and sulfur. Inset: HR-TEM of Lysine@WS2 QDs. (b–f) Elemental mapping of the synthesized Lysine@WS2 QDs.
Figure 2
Figure 2
(a) UV–vis, (b) FTIR, and (c) Raman spectra of WS2 QDs & Lysine@WS2 QDs.
Figure 3
Figure 3
(a) XRD Pattern of functionalized and non-functionalized WS2 QDs, (b) surface tension measurement of lysine, WS2 QDs, & Lysine@WS2 QDs, (c) CV of sequentially modified electrode in buffer containing [Fe(CN)6]3–/4–, and (d) Nyquist plot of the sequentially modified electrode in buffer containing [Fe(CN)6]3–/4–.
Figure 4
Figure 4
(a) Fluorescence spectra of Lysine@WS2 QDs as a function of excitation wavelength. (b) Possible reaction pathway for peroxidase activity of Lysine@WS2 QDs. (c) Absorbance spectrum of Lysine@WS2 QDs-catalyzed H2O2-TMB reaction revealing peaks at 450 and 652 nm. (d) Absorbance spectra of different reaction mixtures (A: lysine WS2 QDs, B: TMB + H2O2, C: TMB + Lysine@WS2 QDs, D: TMB + Lysine@WS2 QDs + H2O2).
Figure 5
Figure 5
(a) Absorbance spectra of Lysine@WS2 QDs in the presence of varying concentrations of H2O2. The inset shows the variation in color intensity with concentration. (b) Calibration for estimating the H2O2 concentration.
Figure 6
Figure 6
(a) Response time study with WS2 QDs & Lysine@WS2 QDs. (b,c) Effect of TMB concentration & calibration function. (d) Effect of Lysine@WS2 QDs volume on the catalytic reaction. (e) Effect of pH. (f) Effect of temperature. (g) Reproducibility study.(h) Effect of interfering species.
Figure 7
Figure 7
(a) Nyquist plot of SPE/Lysine@WS2 QDs in the presence of H2O2 (0.1–350 μM) on the Lysine@WS2 QDs-modified SPE. (b) Effect of pH variation on the sensors response. (c,d) Nyquist plot for reproducibility and interference study, respectively.
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