Evaluation of a minimally invasive glucose biosensor for continuous tissue monitoring

Abstract

We describe here a minimally invasive glucose biosensor based on a microneedle array electrode fabricated from an epoxy-based negative photoresist (SU8 50) and designed for continuous measurement in the dermal compartment with minimal pain. These minimally invasive, continuous monitoring sensor devices (MICoMS) were produced by casting the structures in SU8 50, crosslinking and then metallising them with platinum or silver to obtain the working and reference electrodes, respectively. The metallised microneedle array electrodes were subsequently functionalised by entrapping glucose oxidase in electropolymerised polyphenol (PP) film. Sensor performance in vitro showed that glucose concentrations down to 0.5 mM could be measured with a response times (T90) of 15 s. The effect of sterilisation by Co60 irradiation was evaluated. In preparation for further clinical studies, these sensors were tested in vivo in a healthy volunteer for a period of 3–6 h. The sensor currents were compared against point measurements obtained with a commercial capillary blood glucometer. The epoxy MICoMS devices showed currents values that could be correlated with these. Graphical AbstractMicroneedle arrays for continuous glucose monitoring in dermal interstitial fluid

A Simple Paper Based Microfluidic Electrochemical Biosensor for Point‐of‐Care Cholesterol Diagnostics

“…Figure (a) shows the chronoamperometric curves obtained at a potential of 0.6 V as a function of cholesterol concentration. The value of current initially decays with increase in time (at all measured cholesterol concentrations) according to Cottrell equation (Figure (a)) and then approaches saturation . With increase in concentration of cholesterol from 0.12 to 10.23 mM, the saturation current is observed to increase continuously from 3.6 to 17.7 µA.…”

“…The value of current initially decays with increase in time (at all measured cholesterol concentrations) according to Cottrell equation (Figure 6(a)) and then approaches saturation. [19] With increase in concentration of cholesterol from 0.12 to 10.23 mM, the saturation current is observed to increase continuously from 3.6 to 17.7 mA. The mechanism behind this increment in current is the catalytic reaction of free cholesterol in the presence of immobilized ChOx enzyme as given below [20] :…”

Microneedle Array‐Based Platforms for Future Theranostic Applications

“…(Sharma, 2018) So far, MNAs have been modified to fabricate electrochemical sensors and used for monitoring metabolites (glucose and lactate), drugs such as theophylline and penicillin (Rawson 2017). This is done either entrapping the molecular recognition element (in the case of glucose sensors it is the enzyme glucose oxidase) either in a polymer such as electropolymerised polyphenol (Sharma, 2016) or in hydrogels on platinum or graphene (Lee, 2016) coated MNAs.…”

Editors' Choice—Review—In Vivo and In Vitro Microneedle Based Enzymatic and Non-Enzymatic Continuous Glucose Monitoring Biosensors

“…Sharma et al fabricated a minimally invasive glucose biosensor based on a microneedle array electrode from an epoxy-based negative photoresist (SU8 50) material and designed for continuous measurement in the dermal compartment with minimal pain. 40 The sensor device consisted of a three-dimensional out of plane microneedle array, with 64 microneedles perpendicular to the basal plate and arranged as four 4 × 4 arrays (Figures 2A and 2B). Fabrication procedure of microneedle array electrode involves (a) making of aluminum masters using an electrical discharge machining (EDM) technique to create moulds of polydimethoxy siloxane (PDMS); (b) the PDMS moulds were subsequently used to cast SU8 50 using vacuuming and spinning; (c) crosslinking of SU8 50 by exposure to UV light at λ 365nm for 30 min; (d) peeling off the final epoxy sensor devices from the PDMS layer and subsequent metallization of the sensor devices by conformal sputtering in a clean room to produce the working and reference electrodes.…”