A multiparametric, non-invasive, and reagentless sensing strategy for diabetic monitoring is proposed based on a bespoke graphite ink “writable” formulation (including biocompatible binders and modifiers) used as a conductive layer for glucose oxidase immobilisation within an epidermal patch. This enables the encapsulation of heterocyclic quinoid species 1,10-phenanthroline-5,6-dione 1 which acts as a proton and electron acceptor for FADH2 cofactor regeneration. The surface characterisation of the ink layer was achieved via FTIR, thermal analysis (TGA/DSC), and scanning electron microscopy. Voltammetric and pulse techniques establish analytical performance criteria for the mediated device over physiological glucose levels in sweat (10-200 mM 2) at neutral pH levels. Hygroscopic hydrogels (chitosan/poly vinyl alcohol) and nanofibrous mats form overlaid membranes as sweat collection zones, sandwiched beneath a cotton fabric wicking layer for fingertip perspiration harvesting.
The prototype electronic control system involves a customisable Arduino-based potentiostat 3 with off-the-shelf electronic components capable of performing electrochemical measurements, as well as recording temperature and galvanic skin sensor responses (GSR) 4. The addition of electrodermal activity via a GSR sensor detection module and a temperature probe makes for a multiparametric system which responds to electrical activity in the skin due to the variation in moisture levels due to sweating. GSR reflects sweat gland activity and changes in the sympathetic nervous system, as well as the activity of the sweat glands in response to sympathetic nervous stimulation4. Calibration parameters can thus be adjusted dynamically relative to changes in temperature and other measurement variables. Such a system requires small sample volumes (<50 mL), provides rapid time to result <1 min, and is portable and disposable. The integration of allied electronics has the potential to carry out transduction and wireless transmission, enabling smart and remote healthcare.
