Thin-Film Drug Delivery Coatings to Mitigate the Reactive Tissue Response Associated with Neuroprosthetic Micro-Electrode Implantation
Abstract
The chronic implantation of cortical micro-electrode arrays offers a possible avenue to restore lost function to those suffering from neurological disease or damage. By implanting a micro-electrode array (MEA) into a small population of functional neurons, one may record discrete neural signals, which once decoded may be used to control a prosthetic device. Similarly, feedback from sensors on the device may be encoded and used to stimulate neurons allowing for the transmission of information back to the brain. One major drawback to this approach, however, is the highly invasive nature of the devices themselves. At the moment of implantation of cortical MEAs, the foreign body response (FBR) is initiated. Activating an inflammation cascade which leads to the formation of a glial scar that acts as a physical barrier between the array and the local neuron population. The activation of the FBR has been found to correlate with both an increase of impedance and a decrease in signal to noise of the electrodes upon the MEA. As time progresses, signals attenuate until these devices ultimately fail. This research attempted to design a macro-scale substrate model for the analysis of two independent drug delivery systems which could ultimately be used to combat specific stages of the FBR in an attempt to prolong device functionality. The use of thin-film sol-gel and layer-by-layer technologies were implemented onto a silicon wafer substrate to determine their impact on drug loading and release, as well as thickness. Once optimized, these technologies were used to coat functional MEA devices to investigate the impact on relative change in device thickness, electrical impedance and charge carrying capacity. These findings were used to determine the functionality of each coating strategy and their utility in FBR mitigation and extending device functionality. Use of these coating assessment methods and the findings from the coating strategies will aid in developing a solution to prolong the lifetime of chronically implanted neural devices.
Degree
Ph.D.
Advisors
Panitch, Purdue University.
Subject Area
Polymer chemistry|Biomedical engineering
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