Polymer Indicator Displacement Assay: Electrochemical Glucose Monitoring Based on Boronic Acid Receptors and Graphene Foam, Gii, Competitively Binding with Poly-Nordihydroguaiaretic Acid
Highlights
- Here, we propose an alternative, low-cost yet effective electrochemical glucose chemo-sensing technique based on a boronic acid functionalisation upon Gii-Sens.
- The new methodology is shown to give apparent saccharide – boronic acid binding constants and to work in human serum, this shows in the future that this could be developed further to develop a glucose monitoring method.
Abstract
The concept of a reversible polymer displacement sensor mechanism for electrochemical glucose monitoring is demonstrated.
A pyrene-derivatised boronic acid chemo-receptor for glucose is adsorbed onto a Gii electrode. Spontaneous oxidative polymerisation of nordihydroguaiaretic acid (NHG) onto the graphene foam electrode leads to a redox active film (poly-NHG) covalently attached to the boronic acid receptors. Oxidation of poly-NHG frees the boronic acid receptors to interact with glucose from the solution phase, which is detected due to competitive binding when reduced poly-NHG re-binds to the boronic acid functional groups.
The sensor shows the anticipated boronic acid selectivity of fructose > glucose. The ratio of charges under the voltammetric peaks for poly-NHG unbound and bound is employed for glucose sensing with an approximately linear analytical range from 1 to 50 mM glucose in aqueous pH 7 buffer.
The new methodology is shown to give apparent saccharide – boronic acid binding constants and to work in human serum. Therefore, in the future it could be developed further for glucose monitoring.
Introduction
Diabetes is a chronic condition in which the sufferer can no longer naturally regulate their own blood glucose levels, either due to not being able to produce insulin (type I) or due to a loss of cell responsiveness to insulin (type II). In both cases, successful diabetes management relies upon accurate and sensitive blood glucose testing methods to inform insulin dosage.
A vast number of glucose detection methods already exists.[1,2] The most common techniques applied to clinical sensing make use of enzymes such as glucose oxidase for electrochemical glucose detection, thereby classifying them as biosensors.[3] However, enzyme-based biosensors are inherently affected by changes in temperature, pH and are dependent on localised oxygen concentration in the analyte, which can lead to reliability issues and may impact upon the ability of the patient to effectively manage their condition.[4]
Furthermore, current electrochemical glucose sensors on the market today are expensive (it is estimated that £172 million was spent on glucose monitors in 2012 by the NHS alone).[5]Therefore, it is clinically and fiscally desirable to uncover new, enzyme-free glucose monitoring sensor solutions.
Here, we propose an alternative, low-cost yet effective electrochemical glucose chemo-sensing technique based on a boronic acid functionalised graphene foam electrode in conjunction with a redox-active polymer. The sensor mechanism relies on temporary polymer displacement.