Electrochemical Detection for Uric Acid Based on β-Lactoglobulin-Functionalized Multiwall Carbon Nanotubes Synthesis with PtNPs Nanocomposite

Abstract

In this work, a simple and highly selective electrochemical biosensor for determination of uric acid (UA) is synthesized by using β-lactoglobulin (BLG)-functionalized multiwall carbon nanotubes (MWCNTs) and a platinum nanoparticles (PtNPs) nanocomposite. Urate oxidase (UOx) can oxidize uric acid to hydrogen peroxide and allantoin, which provides a good opportunity for electrochemical detection for UA. Under the optimized conditions, the current changes by the UOx/Bull Serum Albumin (BSA)/BLG-MWCNTs-PtNPs/Glassy Carbon (GC) electrode with the electrochemical method was proportional to the concentration of UA. According to experiments, we obtained a linear response with a concentration range from 0.02 to 0.5 mM and achieved a high sensitivity of 31.131 μA mM^-1 and a low detection limit (0.8 μΜ). Meanwhile, nanoparticles improved the performance of the biosensor and combined with BLG not only prevented the accumulation of composite nanomaterials, but also provided immobilization of uricase through electrostatic adsorption. This improves the stability and gives the constructed electrode sensing interface superior performance in UA detection.

Keywords: multiwall carbon nanotubes; nanocomposite; urate oxidase; uric acid biosensor; β-lactoglobulin.

Scheme 1

A schematic diagram of the reaction principle and preparation process of the uric acid sensor.

Figure 1

TEM results of MWCNTs (A), BLG-MWCNTs (B), and BLG-MWCNTs-PtNPs (C); EDX spectrum (D) of BLG-MWCNTs-PtNPs nanocomposite; XRD result of BLG-MWCNTs-PtNPs (b) and MWCNTs (a) (E); FT-IR result of BLG-MWCNTs-PtNPs (b) and MWCNTs (a) (F).

Figure 1

TEM results of MWCNTs (A), BLG-MWCNTs (B), and BLG-MWCNTs-PtNPs (C); EDX spectrum (D) of BLG-MWCNTs-PtNPs nanocomposite; XRD result of BLG-MWCNTs-PtNPs (b) and MWCNTs (a) (E); FT-IR result of BLG-MWCNTs-PtNPs (b) and MWCNTs (a) (F).

Figure 2

Cyclic voltammograms (CVs) of GC electrode (a), MWCNTs modified GC electrode (b), BLG-MWCNTs modified GC electrode (c) and BLG-MWCNTs-PtNPs modified GC electrode (d) scanned in 0.1 M KCl solution with 10 mM [Fe(CN)₆]³⁻.

Figure 3

(A) CV responses to 0.9 mM uric acid in various pH conditions (pH = 6.0, 6.5, 7.0, 7.5, 8.0, and 8.5) with UOx/BSA/BLG-MWCNTs-PtNPs/GCE (buffer pH = 7.0, the scanning voltage range −600~800 mV), trends are shown in a histogram (B).

Figure 4

(A) Amperometric response after continuous progressive addition of uric acid (UA) with UOx/BSA/BLG-MWCNTs-PtNPs/GCE in 0.1 M PBS solution under stirring; (B) the calibration curve of the relationship between UA concentration and amperometric value.

Figure 5

Interference experiments of UOx/BSA/BLG-MWCNTs-PtNPs/GCE in pH 7.0 0.1 M PBS solution containing UA or other substances: (A) dopamine (0.1 mM), (B) glutathione (0.2 mM), (C) cysteine (0.2 mM), (D) glucose (0.1 mM), (E) urea (0.2 mM), (F) cholesterol (0.2 mM).