Glucose Biosensor Based on Disposable Activated Carbon Electrodes Modified with Platinum Nanoparticles Electrodeposited on Poly(Azure A)

Abstract

Herein, a novel electrochemical glucose biosensor based on glucose oxidase (GOx) immobilized on a surface containing platinum nanoparticles (PtNPs) electrodeposited on poly(Azure A) (PAA) previously electropolymerized on activated screen-printed carbon electrodes (GOx-PtNPs-PAA-aSPCEs) is reported. The resulting electrochemical biosensor was validated towards glucose oxidation in real samples and further electrochemical measurement associated with the generated H₂O₂. The electrochemical biosensor showed an excellent sensitivity (42.7 μA mM^-1 cm^-2), limit of detection (7.6 μM), linear range (20 μM-2.3 mM), and good selectivity towards glucose determination. Furthermore, and most importantly, the detection of glucose was performed at a low potential (0.2 V vs. Ag). The high performance of the electrochemical biosensor was explained through surface exploration using field emission SEM, XPS, and impedance measurements. The electrochemical biosensor was successfully applied to glucose quantification in several real samples (commercial juices and a plant cell culture medium), exhibiting a high accuracy when compared with a classical spectrophotometric method. This electrochemical biosensor can be easily prepared and opens up a good alternative in the development of new sensitive glucose sensors.

Keywords: activated screen-printed carbon electrodes; enzymatic biosensor; glucose; glucose oxidase; platinum nanoparticles; poly(Azure A).

Figure 1

Anodic linear scan voltammetry (LSV) responses of the different electrode modification steps in the absence (dashed lines) and the presence of 5 mM of H₂O₂ (solid lines). The measurements were performed in 0.1 M PB.

Figure 2

FE-SEM images of: (A) screen-printed carbon electrodes (SPCE), (B) activated SPCE (aSPCE), (C) poly(Azure A) (PAA)-aSPCE, (D) platinum nanoparticles (PtNPs)-PAA-aSPCE, and (E) glucose oxidase (GOx)-PtNPs-PAA-aSPCEs, with a magnification of 30,000 K.

Figure 3

Nyquist plots for the different steps of the working electrode modification: (A) SPCE,(B) aSPCE, (C) PAA-aSPCE, (D) PtNPs-PAA-aSPCE and (E) GOx-PtNPs-PAA-aSPCE. Electrochemical impedance spectroscopy (EIS) was recorded at 0.15 V (vs. Ag) in 1 mM Na₄Fe(CN)₆ (in 0.1 M KCl). Experimental conditions: stabilization time 60 s, amplitude 5 mV, and frequencies 65 kHz–10 mHz, with five points per decade. The inset in (A) shows the equivalent circuit used.

Figure 4

XPS (A) O1s and (B) N1s spectra for PAA-SPCE and PAA-aSPCE. XPS (C) C1s and (D) N1s spectra for PAA-aSPCE and PtNPs-PAA-aSPCE. The insets of the respective figures show the atomic surface concentrations of the functional groups after the deconvolution of the peaks.

Figure 5

Current outcome obtained by successive additions of glucose in a stirred solution (10 mL) of 100 mM PB, pH 7, at 0.2 V (vs. Ag), using a GOx-PtNPs-PAA-aSPCE. Range of glucose concentration: (A) 100−1200 µM; inset of (A), 20−200 µM; and (B) 0.1−6.5 mM. The experimental data of I vs. time from Figure 5B are shown in Figure S5 (Supplementary Material).