Poly(3,4-ethylene dioxythiophene Nanofibers for Neural Interfaces

Open Access
Author:
Layton, Kelly Nicole
Graduate Program:
Bioengineering
Degree:
Master of Engineering
Document Type:
Master Thesis
Date of Defense:
June 23, 2014
Committee Members:
  • Mohammad Reza Abidian, Thesis Advisor
Keywords:
  • Poly(3
  • 4-ethylene dioxythiophene)
  • Nanofibers
  • Conducting Polymers
  • Biomaterials
  • Neural Interfaces
  • Glucose Detection
Abstract:
The ability to directly interface with the nervous system is necessary to better understand the function of this complex system and to gain insight into new methods to treat neural injury and disease. Further, the materials used at the biotic-abiotic interface are critical to the functionality of such therapies. Conducting polymers have shown promise for use in neural interfacing for several reasons: their electrical conductivity, the ability to incorporate and release biomolecules, and the ease of fabricating nano-scale morphologies. Conducting polymers such as polypyrrole and poly(3,4-ethylene dioxythiophene) have been used in applications such as drug delivery, biosensing, neural recording, and tissue engineering. This research focused on developing conducting polymer nanofibers for use in such applications. The first part of this research was the development of a sensitive biosensor using conducting polymer nanofibers. Sensors are fabricated on microelectrodes coated with conducting polymer films or nanofibers with the enzyme glucose oxidase incorporated. The conducting polymer nanofibers were shown to incorporate a larger amount of the enzyme and to have lower impedance than the conducting polymer films. In turn, the nanofibers had a higher sensitivity to glucose than the films and also retained a larger percentage of that sensitivity over time. Finally, the nanofibers showed less of a loss in charge storage capacity over time, which was further enhanced by the use of lower polarization potentials. These biosensors serve as a proof of concept such sensor design in the detection of other neurochemicals and neurotransmitters. The second part of this research was the fabrication and characterization of conductive hydrogel nanofibers using a method that does not require a hard metal substrate. Nanofibers were fabricated from a blend of varying amounts of conducting polymer nanoparticles and hydrogel. The morphology, swelling ratio, and electrical impedance of such nanofibers were measured and compared to films of similar material. Increasing amounts of conducting polymer nanoparticles led to reduced swelling ratios and larger reductions in impedance. Additionally, the film and nanofiber morphologies had distinctly different impedance specta in the low frequency ranges. Such conductive hydrogel nanofibers could find future application in drug delivery or neural tissue engineering.