Multi-walled carbon nanotubes functionalized with a new Schiff base containing phenylboronic acid residues: application to the development of a bienzymatic glucose biosensor using a response surface methodology approach

An innovative supramolecular architecture is reported for bienzymatic glucose biosensing based on the use of a nanohybrid made of multi-walled carbon nanotubes (MWCNTs) non-covalently functionalized with a Schiff base modified with two phenylboronic acid residues (SB-dBA) as platform for the site-specific immobilization of the glycoproteins glucose oxidase (GOx) and horseradish peroxidase (HRP). The analytical signal was obtained from amperometric experiments at − 0.050 V in the presence of 5.0 × 10⁻⁴ M hydroquinone as redox mediator. The concentration of GOx and HRP and the interaction time between the enzymes and the nanohybrid MWCNT–SB-dBA deposited at glassy carbon electrodes (GCEs) were optimized through a central composite design (CCD)/response surface methodology (RSM). The optimal concentrations of GOx and HRP were 3.0 mg mL⁻¹ and 1.50 mg mL⁻¹, respectively, while the optimum interaction time was 3.0 min. The bienzymatic biosensor presented a sensitivity of (24 ± 2) × 10² µA dL mg⁻¹ ((44 ± 4) × 10² µA M⁻¹), a linear range between 0.06 mg dL⁻¹ and 21.6 mg dL⁻¹ (3.1 µM–1.2 mM) (R² = 0.9991), and detection and quantification limits of 0.02 mg dL⁻¹ (1.0 µM) and 0.06 mg dL⁻¹ (3.1 µM), respectively. The reproducibility for five sensors prepared with the same MWCNT–SB-dBA nanohybrid was 6.3%, while the reproducibility for sensors prepared with five different nanohybrids and five electrodes each was 7.9%. The GCE/MWCNT–SB-dBA/GOx-HRP was successfully used for the quantification of glucose in artificial human urine and commercial human serum samples.

Graphical Abstract