Development of an enzymatic glucose biosensor for applications in wearable sweat-based sensing
The recent development and commercial availability of wearable devices like the FITBITÃ Â® and Apple WatchÃ Â® reflect an increasing consumer interest in actively monitoring health parameters. Though wearable devices are beginning to emerge in a variety of fields and applications, there is particular interest in the development of wearable monitors for continuously sensing blood glucose levels. Diabetes currently affects nearly 10% of the American population, a number that is expected to rise in the near future, prompting increased interest in noninvasive methods of monitoring glucose levels. This interest in noninvasive monitoring and the recent advent of continuous monitoring products like the FITBITÃ Â® are coupled together in the concept of wearable glucose sensors that utilize sweat glucose concentration levels as a means to monitor blood glucose concentration.
This work centers on sweat-based glucose biosensors with applications in continuous monitoring for diabetes patients. It includes an overview of glucose biosensors and an introduction to electrochemistry (Chapter 1) and an investigation into the effectiveness of electrodeposited platinum nanoparticles as a transduction element in electrochemical glucose biosensor (Chapter 2).
A large part of this thesis (Chapter 3) is devoted to the development of an entirely inkjet printable working electrode for applications in wearable sensing. The developed electrode was fabricated entirely through inkjet printing using a commercially available Fujifilm Dimatix Materials Printer and characterization tests show that the sensor performs similarly to sensors fabricated using more costly and time-intensive clean room methods. The sensor consists of a conductive graphene underlayer, an insulative lacquer coating which serves to maintain constant electrode surface area, a transduction layer of platinum-decorated carbon nanotubes, a detection layer of glucose oxidase and stabilizing protein bovine serum albumin, and finally, a cross-linking layer of glutaraldehyde. When operating in phosphate buffer solution the sensor demonstrates a linear sensing range of 10 Ã ÂµM to 2.51 mM glucose, which is within the range of sweat glucose concentrations, a response time of 18 seconds, average sensitivity of 18.09 Ã ÂµA mM-1 cm-2, and a theoretical detection limit of 3.79 Ã ÂµM glucose.