Date on Master's Thesis/Doctoral Dissertation

12-2014

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Electrical and Computer Engineering

Committee Chair

Walsh, Kevin Michael, 1955-

Committee Co-Chair (if applicable)

Keller, Bradley B.

Committee Member

Naber, John F.

Committee Member

McNamara, Shamus

Subject

Tissue engineering; Biomedical engineering; Thin films; Nanostructured materials--Health aspects; Nanowires

Abstract

Electrical stimulation has been increasingly used by research groups to enhance and increase maturation of cells in an engineered cardiac tissue (ECT). Current methods are based on using off-the-shelf wires or electrodes to deliver a stimulus voltage to the in-vitro tissue in culture medium. A major issue with this approach is the generation of byproducts in the medium due to the voltage levels required, which are typically in the range of 5V-10V. No solution currently exists that can accomplish electrical stimulation of cells in an ECT at a low voltage level. Therefore, in this study a novel, porous, thinfilm, microelectrode array (PMEA) device is proposed. The primary advantage of this device is the ability to successfully function at a very low voltage thus minimizing any undesirable oxidative byproducts in the culture environment or cell injury. This was achieved by designing and fabricating a thin device capable of being embedded in the ECT to deliver voltage. The P-MEA device is essentially a thin-film cable i.e. a conducting wire encapsulated with an insulating material; in this case thin-film gold electrodes sandwiched between two layers of insulating polyimide. Major features of the P-MEA include overall dimensions of 10mm width and 82mm length, four arms to allow movement of the individual sensor pads within ECTs, each embedded electrode arm incorporates eight 100μm x 200μm rectangular pores surrounding a 950μm x 340μm exposed electrode, large pads on either side of the porous embedded sensor to function as return electrodes, suture holes to aid in-vivo suturing and stabilization and eight electrode connector pads. Average thickness of the device was 16μm, with an average electrode film thickness of 0.4μm. Electrode resistance ranged from 69.45Ω to 78.52Ω. Electrochemical impedance spectroscopy was performed on the P-MEA electrodes and it confirmed that the P-MEA successfully operates in the 0.01V to 1.0V range with favorable charge transfer characteristics. Proof of principle experiments confirmed the ability of the PMEA to effectively embed within the ECT and electrically stimulate it during chronic, in-vitro culture. Histology imaging shows that the embedding of the device has no adverse effects on the ECT and the cardiomyocytes are aligned within the tissue. Experiments are ongoing to evaluate the role of electrical stimulation on the maturation and function of ECTs which are made of stem cells and other sources. In summary, this device is capable of safe low-voltage electrical stimulation of engineered cardiac tissues (ECTs); it has been designed, fabricated, and its ability to function as a low-voltage stimulus device has been validated using electrochemical tests and in-vitro culture experiments. The design and fabrication of the device went through three major iterations. A final manufacturing process was refined and successfully transferred to the UofL MNTC staff for subsequent manufacturing.

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