Human stress monitoring through an organic cotton-fiber biosensor

Abstract

Selective detection of bioanalytes in physiological fluids, such as blood, sweat or saliva, by means of lowcost and non-invasive devices, is of crucial importance to improve diagnosis and prevention in healthcare.To be really useful in everyday life a sensing system needs to be handy, non-invasive, easy to read and possibly wearable. Only a sensor that satisfies these requirements could be eligible for applications in healthcare and physiological condition monitoring. Herein an organic electrochemical transistor has been investigated as a simple, low-cost and e-textile biosensor, fully integrated on a single cotton yarn.The biosensor has been used for real-time detection of adrenaline, selectively compared to the saline content in human physiological fluids. The sensing mechanism is based on the oxidation of adrenaline at the Pt-gate electrode surface, with the formation of adrenaline-quinone and adrenochrome. Two independent organic electrochemical transistors, characterized by different gate-electrode materials, detect saline and adrenaline concentrations, respectively, in real human sweat. Measurements performed in real-time mode show the complete independence of adrenaline detection from NaCl and, hence, guarantee the simultaneous monitoring of both concentrations. The oxidation of adrenaline has been studied by means of absorption spectroscopy in air, with either silver or platinum working electrodes.Our results confirm that the oxidation reaction driven by the Pt-electrode leads to the formation of adrenochrome, while with the Ag-electrode the oxidation is similar to the spontaneous one occurring in air. The cotton-based biosensor shows the possibility of monitoring human performances (hydration and stress) in situ and using a non-invasive approach, opening new unexplored opportunities in healthcare, fitness and work safety.

Organic Electrochemical Transistors Based on Room Temperature Ionic Liquids: Performance and Stability

“…OECTs are based on conducting polymers such as PEDOT: PSS, which can be processed at low temperatures on flexible substrates with large areas . Being able to conduct both, electronic and ionic charge, PEDOT:PSS has been widely adopted to transduce ionic signals into electronic signals and to detect ions, metabolites, hormones, DNA, and dopamine, as well as to record brain activity, to detect lactate acid, to detect the activity of electrically active cells or tissues, or to drive an active matrix display …”

“…OECTs are based on conducting polymers such as PEDOT: PSS, [1] which can be processed at low temperatures on flexible substrates with large areas. [2] Being able to conduct both, electronic and ionic charge, PEDOT:PSS has been widely adopted to transduce ionic signals into electronic signals and to detect ions, [3] metabolites, [4] hormones, [5] DNA, [6] and dopamine, [7] as well as to record brain activity, [8,9] to detect lactate acid, [10] to detect the activity of electrically active cells or tissues, [11] or to drive an active matrix display. [12] Since the operation mechanism of OECTs is based on doping or de-doping of a conducting polymer, in recent years researchers have been focusing on optimizing the semiconducting materials suitable for OECTs.…”

Fabrication and Use of Organic Electrochemical Transistors for Sensing of Metabolites in Aqueous Media

“…If the transistor substrate is represented by natural cotton fibers, deposition of the active layer can be simply achieved by soaking the yarns into a suspension containing the polymer to be deposited. Coppedè et al [121] followed this method to fabricate OECTs-based adrenaline biosensors. They used a commercial PEDOT:PSS suspension, modified with ethylene glycol (20%) and dodecyl benzene sulfonic acid (12%) to increase electrical conductivity and reduce solubility in water, in which cotton yarns where soaked for 5 min, followed by baking at 150 • C for 3 h on a hot plate.…”

“…Coppedè et al [121] developed an e-textile integrated biosensors encompassing a cotton yarn functionalized with PEDOT:PSS, a Pt-wire used as gate electrode and human sweat as electrolyte ( Figure 16, see also Section 3.3.5). The detection of adrenaline concentration above 1 µM has efficiently been performed.…”

“…Plots of the normalized transistor response at different concentrations of adrenaline from 10 −8 to 10 −3 M, with a Pt-gate electrode at two different NaCl concentrations (10 −1 and 10 −2 M) (right). Reproduced from[121] with permission of The Royal Society of Chemistry.…”