A Homogeneous Colorimetric Strategy Based on Rose-like CuS@Prussian Blue/Pt for Detection of Dopamine

Abstract

The development of effective methods for dopamine detection is critical. In this study, a homogeneous colorimetric strategy for the detection of dopamine based on a copper sulfide and Prussian blue/platinum (CuS@PB/Pt) composite was developed. A rose-like CuS@PB/Pt composite was synthesized for the first time, and it was discovered that when hydrogen peroxide was present, the 3,3',5,5'-tetramethylbenzidine (TMB) changed from colorless into blue-oxidized TMB. The CuS@PB/Pt composite was characterized with a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and an X-ray photoelectron spectrometer (XPS). Moreover, the catalytic activity of the CuS@PB/Pt composite was inhibited by the binding of dopamine to the composite. The color change of TMB can be evaluated by the UV spectrum and a portable smartphone detection device. The developed colorimetric sensor can be used to quantitatively analyze dopamine between 1 and 60 µM with a detection limit of 0.28 μM. Furthermore, the sensor showed good long-term stability and good performance in human serum samples. Compared with other reported methods, this strategy can be performed rapidly (16 min) and has the advantage of smartphone visual detection. The portable smartphone detection device is portable and user-friendly, providing convenient colorimetric analysis for serum. This colorimetric strategy also has considerable potential for the development of in vitro diagnosis methods in combination with other test strips.

Keywords: colorimetric; dopamine; rose-like CuS@Prussian blue/Pt; smartphone.

Figure 1

(a) Schematic illustration of a CuS@Pb/Pt colorimetric sensor for DA. (b) Two methods for detecting dopamine. (Coloured lines for UV-vis absorption spectroscopy; Shades of blue for visible color of DA) (c) The schematic representation of the portable device.

Figure 2

SEM images of (a) CuS, (b) CuS@PB, and (c) CuS@PB/Pt. (e) XPS spectra of the CuS@PB/Pt. XPS spectra of (f) C 1_S, (g) Cu 2p, (i) S 2p, (j) Pt 4f, and (k) Fe 2p. (d,h,l) The corresponding EDS elemental mapping images of the prepared CuS@PB/Pt, including the S, Cu, Fe, and Pt. Scale bar: 2 nm.

Figure 3

(a) Responses of UV-vis spectra of various materials to TMB and H₂O₂ at the same concentration (1.0 mg/mL). (b) Responses of the UV-vis spectra of CuS@Pb/Pt (1.0 mg/mL) reacted with TMB with or without H₂O₂. (c) Responses of UV-vis spectra to the addition of DA at different concentrations.

Figure 4

(a) UV-vis absorption spectra with different pHs of PBS (0.01 M) buffer. (b) UV-vis absorption spectra with different reaction temperatures. (c) UV-vis absorption spectra with different reaction times.

Figure 5

(a) Linear curve of UV-vis spectra responses in the DA from 1 to 60 μM. (b) Linear curve of RGB colorimetry in the DA from 1 to 10 μM. (c) Matching visible color in the DA range of 1 to 60 μM.

Figure 6

(a) Specificity of the established method for the DA of UV-vis spectra responses (other interfering compounds are present in concentrations five times (50 μM) greater than DA’s. (e) Specificity of the established method for DA of RGB colorimetric (△R = R − R_blank). (b,f) The UV-vis spectra responses and RGB colorimetric values of DA, AA, and coexisting systems. The concentration of interferents is three times higher than that of DA (10 μM). (c,g) The repeatability of the developed method (DA = 10 µM). (d,h) The 30-day storage stability of the established method (DA = 50 µM for UV-vis spectra, DA = 5 µM for RGB colorimetric).

Figure 7

(a) Linear curve of peak area versus dopamine concentration. (b) Fitting curve of HPLC-MS/MS and UV-vis signal. (c) Fitting curve of HPLC-MS/MS and smart phone signal.