Functionalized graphene oxide for clinical glucose biosensing in urine and serum samples

Abstract

A novel clinical glucose biosensor fabricated using functionalized metalloid-polymer (silver-silica coated with polyethylene glycol) hybrid nanoparticles on the surface of a graphene oxide nanosheet is reported. The cyclic voltammetric response of glucose oxidase modification on the surface of a functionalized graphene oxide electrode showed a surface-confined reaction and an effective redox potential near zero volts, with a wide linearity of 0.1–20 mM and a sensitivity of 7.66 μA mM⁻¹ cm⁻². The functionalized graphene oxide electrode showed a better electrocatalytic response toward oxidation of H₂O₂ and reduction of oxygen. The practical applicability of the functionalized graphene oxide electrode was demonstrated by measuring the peak current against multiple urine and serum samples from diabetic patients. This new hybrid nanoarchitecture combining a three-dimensional metalloid-polymer hybrid and two-dimensional graphene oxide provided a thin solid laminate on the electrode surface. The easy fabrication process and retention of bioactive immobilized enzymes on the functionalized graphene oxide electrode could potentially be extended to detection of other biomolecules, and have broad applications in electrochemical biosensing.

Keywords:

• clinical diagnostics
• glucose biosensor
• metalloid-polymer nanoparticles
• glucose oxidase
• cyclic voltammetry

Acknowledgment

This research was supported by grants from the Ministry of Knowledge and Economy (10039863) to KSYun and the Ministry of Knowledge and Economy (10032112) to M-HLee.

Disclosure

The authors report no conflicts of interest in this work.

Supplementary materials

Table S1 Shows the patient details in terms of their age, gender and glucose concentration measured by commercial sensor Accu-Chek^® from Roche (Basel, Switzerland)

Figure S1. (A) Ultraviolet-visible absorbance spectrum, and (B) particle size distribution histogram of metalloid polymer hybrid nanoparticles (Ag@SiO₂-PEG) from electrophoretic light scattering measurements. (C) Field emission scanning electron microscopic (scale bar 30 nm) and (D) high resolution transmission electron microscopic images (scale bar 10 nm) of metalloid polymer hybrid nanoparticles.

Abbreviations: Ag@SiO₂-PEG, silver-silica coated with polyethylene glycol; LS int., light scattering intensity.

Figure S2. Fourier transform infrared absorbance spectra of (A) GO, (B) MPHs, and (C) FGO.

Abbreviations: GO, graphene oxide; MPHs, metalloid polymer hybrid nanoparticles; FGO, functionalized graphene oxide.

Figure S3. CVs of Au-PCB-FGO-GOx versus different clinical glucosuria samples (urine samples from five patients named A–E) at volumes of 10, 60, and 160 μL in phosphate-buffered solution. (F) Cathodic peak current histogram for five glucosuria samples.

Notes: This result shows the preliminary clinical diagnostics of urine samples from hyperglycemic patients. Scan rate: 50 mV/s.

Abbreviations: CVs, cyclic voltammograms; Au-PCB-FGO-GOx, gold printed circuit board electrode modified with functionalized graphene oxide and glucose oxidase; Ag/AgCI, silver/silver chloride.

Figure S4. Multiple cycle CV segments of Au-PCB-FGO-GOx versus glucose serum sample (glucose concentration in serum 131 mg/dL, measured by Accu-Chek^®) electrode measured on day 0 (A, black trace) and after 50 days (B, red trace) stored in refrigeration at 4°C.

Note: Scan rate: 50 mV per second.

Abbreviations: CV, cyclic voltammogram; Au-PCB-FGO-GOx, gold printed circuit board electrode modified with functionalized graphene oxide and glucose oxidase; Ag/AgCI, silver/silver chloride.