Preparation of Graphene-Modified Acupuncture Needle and Its Application in Detecting Neurotransmitters

Abstract

We report a unique nanosensing platform by combining modern nanotechnology with traditional acupuncture needle to prepare graphene-modified acupuncture needle (G-AN), and using it for sensitive detection of neurotransmitters via electrochemistry. An electrochemical deposition method was employed to deposit Au nanoparticles (AuNPs) on the tip surface of the traditional acupuncture needle, while the other part of the needle was coated with insulation paste. Subsequently, the G-AN was obtained by cyclic voltammetry reduction of a graphene oxide solution on the surface of the AuNPs. To investigate the sensing property of the G-AN, pH dependence was measured by recording the open circuit potential in the various pH buffer solutions ranging from 2.0 to 10.0. What's more, the G-AN was further used for detection of dopamine (DA) with a limit of detection of 0.24 μM. This novel G-AN exhibited a good sensitivity and selectivity, and could realize direct detection of DA in human serum.

Figure 1. The fabrication process for the preparation of the G-AN and the detection of DA by the G-AN.

(A) The schematic plot of a G-AN; (B) The optical image of an acupuncture needle; (C) (i) Modification of AuNPs on the tip surface of the acupuncture needle; (ii) Deposition of graphene via electrochemistry method; (iii) Measurement of DA using the G-AN. All parts of this figure were drawn by FY. The optical image of the acupuncture needle was taken by LT.

Figure 2. SEM images of the

(A) bare acupuncture needle, (B) AuNPs/acupuncture needle, and (C) G-AN. (D) Typical CV obtained at the different nanomaterial-modified acupuncture needle ((a) bare acupuncture needle, (b) AuNPs/acupuncture needle, (c) G-AN, in aqueous solution consisting of 5 mmol/L of K₃[Fe(CN)₆] and 0.1 mol/L of KCl. (E) CVs for acupuncture needle with 10 cycles ((a) modified by AuNPs, (b) modified by ERGO/AuNPs). The voltage range: −0.2 to 0.6 V; scan rate: 100 mV/s.

Figure 3

(A) Time dependence of the open circuit potential of the G-AN in PBS solutions at different pH values, (B) Plots of the potential versus various pH. Y = 0.0209–0.0299X, R² = 0.9921.

Figure 4

(A) DPVs of different acupuncture needles in the solution of 0.1 mM DA ((a) bare acupuncture needle, (b) AuNPs/acupuncture needle, (c) ERGO/acupuncture needle and (d) G-AN). (B) DPVs of the G-AN in the solution of 0.1 mM DA and 1 mM AA. Scan rate, 50 mV/s. (C) The DPVs versus increasing DA concentrations of 0, 1, 2, 4, 6, 8, 10, 20, 40, 60, 80 and 100 μM (from top to bottom). (D) In the inset, the calibration curve of DPVs versus DA concentrations (1 to 10 μM) was represented by Ip(μA) = −0.0293C _DA (μM)-0.3033, R² = 0.9841.

Figure 5. Current responses for the G-AN in the detection of DA (100 μM) in buffer and human serum.