New approaches to enable more effective management of diabetes mellitus, such as continuous glucose monitoring are being developed both to prevent unstable episodes of hypo or hyper glycaemia and also to provide an improved user experience. One emerging approach to realize these requirements is to fabricate a minimally invasive transdermal sensor for the direct in vivo detection of glucose in the interstitial fluid. Microneedles -sharp, microscopic structures measuring less than 1 mm in length -have been previously employed to allow painless penetration of the stratum corneum for delivery of drugs and vaccines. In this work we present, ultra sharp gold coated polymer microneedle arrays (sub micron tip radii) which are fabricated using a low cost polymer replication approach. Critical dimensions of the microneedle arrays are characterized using a combination of optical and scanning electron microscopies. Fabricated microneedle devices are characterized by cyclic voltammetry to explore functionality. The voltammetric detection of glucose is performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the physiological range (2 -13.5 mM). The sensors demonstrate high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol). This demonstrates potential future use of these microneedle devices for in vivo glucose detection.
We report the microfabrication and characterization of gold microband electrodes on silicon using standard microfabrication methods, i.e., lithography and etching techniques. A two-step electrodeposition process was carried out using the on-chip platinum reference and gold counter electrodes, thus incorporating glucose oxidase onto a platinum-modified, gold microband electrode with an o-phenylenediamine and ß-cyclodextrin mixture. The as-fabricated electrodes were studied using optical microscopy, scanning electron microscopy, and atomic force microscopy. The two-step electrodeposition process was conducted in low sample volumes (50 µL) of both solutions required for biosensor construction. Cyclic voltammetry and electrochemical impedance spectroscopy were utilised for electrochemical characterization at each stage of the deposition process. The enzymatic-based microband biosensor demonstrated a linear response to glucose from 2.5–15 mM, using both linear sweep voltammetry and chronoamperometric measurements in buffer-based solutions. The biosensor performance was examined in 30 µL volumes of fetal bovine serum. Whilst a reduction in the sensor sensitivity was evident within 100% serum samples (compared to buffer media), the sensor demonstrated linear glucose detection with increasing glucose concentrations (5–17 mM).
We report a two-step
electrodeposition process incorporating glucose oxidase onto a platinum-
modified gold microband electrode with an o-phenylenediamine and ß-cyclodextrin
mixture. The bare microband electrodes were fabricated on silicon using
standard microfabrication methods i.e. lithography and etching techniques. The
two-step electrode modification process was characterized using cyclic
voltammetry, electrochemical impedance spectroscopy and scanning electron
microscopy. The enzymatic based microband biosensor exhibited a linear response
to glucose from 2.5-15 mM using both linear sweep voltammetry and
chronoamperometric measurements in buffer based solutions. The resulting
miniaturized glucose sensor presented a number of advantages such as ease of
use, fast response time, measuring within physiologically relevant glucose concentrations
in addition to sensing in small sample volumes without the need for an external
counter and reference electrode. The biosensor performance was tested in 30 µl
volumes of undiluted fetal bovine serum. Whilst a reduction in signal was
evident within 100 % serum samples, the sensor achieved linear glucose
detection with increasing glucose concentrations (2-12 mM).
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