An enzyme-less bis-boronic acid modified electrode for glucose sensing in human blood serum

Platforms for measuring the concentration of D-glucose in blood are clinically important in managing diabetes and determining energy resources within the body. Most current glucose sensors utilise the activity of the enzyme glucose oxidase (GOx) to measure glucose concentration. However, as GOx is a biological enzyme its catalytic activity can be susceptible to environmental factors including variations in temperature, humidity, pH and the presence of toxic chemicals. Potential benefits therefore exist in using enzyme-less recognition elements that are less susceptible to degradation and are easily immobilised onto sensors.

We have studied the performance of bis-boronic acids (BA) for use as glucose recognition elements on electrochemical impedance sensing platforms. Bis-boronic acids have been previously used to detect glucose (and other molecules/ions) using fluorescence and amperometry/potentiometry. We report the use of Electrochemical Impedance Spectroscopy with surface immobilised bis-boronic acids to produce a stable and sensitive platform for measuring D-glucose levels in human blood serum.

We have investigated the surface immobilisation steps by altering the ratios of BA with the small ‘filler’ molecule, mercaptopropanol (MCP) and have optimised this ratio to provide the greatest measurement stability. We have found that the detection range is within 0-5 mM for D-glucose but the largest changes in charge transfer resistance (Rct) take place between 0 and 0.5 mM D-glucose. The Rct responses to other serum components; urea, BSA and fructose were also investigated.

These promising results pave the way towards the combination of multiple types of bis-boronic molecules onto a single, multiplexed electrochemical platform to detect a range of saccharides, anions and glycated proteins in complex samples.