A cellulose/β-cyclodextrin nanofiber patch as a wearable epidermal glucose sensor

Abstract

In this study, we aimed to develop a cellulose/β-cyclodextrin (β-CD) electrospun immobilized GOx enzyme patch with reverse iontophoresis for noninvasive monitoring of interstitial fluid (ISF) glucose levels (0.1-0.6 mM dm^-3). In vitro analysis, performed using a sensor attached to flexible substrates, revealed that the high diffusion coefficient (9.0 × 10^-5 cm² s^-1), the linear correlation coefficient (R ² = 0.998), the detection limit (9.35 × 10^-5 M), and the linear range sensitivity (0-1 mM) of the sensor (5.08 μA mM^-1) remained unaffected by the presence of interfering substances (e.g., fructose, sucrose, uric acid, and acetaminophen) at physiological levels. The present results indicate that the new epidermal sensing strategy using nanofibers for continuous glucose monitoring has potential to be applied in diagnosis of diabetes.

Fig. 1. SEM images of cellulose (a), cellulose/β-CD (b), and cellulose/β-CD/GOx (c) nanofibers and the swelling ratio of the cellulose and cellulose/β-CD nanofibers (d).

Fig. 2. X-ray diffraction patterns of CA, cellulose, CA/β-CD, and cellulose/β-CD/GOx nanofibers.

Fig. 3. (a) Cyclic voltammetric measurement of current vs. scan rate. (b) Plot of i vs. t^−1/2 obtained upon chronoamperometry for cellulose/β-CD/GOx nanofiber biosensors in phosphate buffer solution containing 0.1 and 0.5 mM glucose, with an applied potential of −0.2 V vs. an Ag/AgCl electrode.

Fig. 4. (a) Amperometric responses to successive addition of glucose in 0.1 M phosphate buffer solution at −0.2 V (vs. Ag/AgCl). (b) Effect of interfering materials including 1 mM fructose, sucrose, uric acid, acetaminophen, and glucose on the determination of glucose levels. (c) The calibration curve (current versus glucose concentration) obtained from the chronoamperometric current response from 0.1 mM to 5.0 mM. (d) The steady-state calibration curve from 0.1 mM to 1.0 mM. (e) A schematic representation of iontophoresis printable electrodes. (f) Mechanism of iontophoresis on the epidermal cellulose/β-CD/GOx NFs glucose sensor.