Fabrication and Characterization of Biodegradable Microspheres for Applications in Electrically Conductive Biomedical Devices

Open Access
Author:
Antensteiner, Martin
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 15, 2015
Committee Members:
  • Mohammad Reza Abidian, Thesis Advisor
Keywords:
  • Bioelectronics
  • Electrically Conducting Polymer
  • PLGA
  • microsphere
  • electrospraying
  • Impedance
  • Fabrication
Abstract:
A novel method to fabricate uniform, biodegradable microspheres from poly(lactic-co-glycolic acid) (PLGA) 85:15 using an electrospraying process is outlined in this thesis. Initial optimization of PLGA solution parameters discovered that 4wt% PLGA in chloroform yielded microstructures with a smooth, spherical morphology. The addition of benzyltriethylammonium chloride (BTEAC, 2% (w/w) PLGA) increased the conductivity of the solution, and reduced the coefficient of variance (CV) for microsphere diameter from >20% to 14%. Furthermore, modifications of applied potential and spinneret-collector separation distances during electrospraying improved the microsphere diameter to 11% CV. The fabrication parameters were finalized by the addition of silicon wafer substrates bearing Ti/Au (10/100nm) dual layer electrodes with 1.5mm diameter working areas. Resulting microspheres had an average diameter of 3.23±0.23µm and showed a 7% CV. This method was then applied to exploratory research in fabricating conductive biomedical devices through the electrochemical polymerization of polypyrrole (PPy) for 1 minute on PLGA microspheres. Electrical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CVt) was performed using a bare gold reference electrode to characterize the electrical properties. The fabricated conducting polymer-based electrodes showed promising 10% and 23% impedance decreases at 1 kHz and 100 Hz respectively relative to the bare gold reference. The charge storage capacity of these devices was improved over bare gold electrodes by 20%. Based on these observations, the PLGA microsphere fabrication route presented in this thesis shows promise for the development of conductive biomedical devices.