THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Tuesday, May 7, 2019

10:00 AM

in Marcus 1116

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Eleanor Brightbill

"Improving signal reliability in fast biosensing platforms: sensor surface structure and solution interactions"

Committee Members:

Prof. Eric Vogel, Advisor, MSE

Prof. Valeria Milam, MSE

Prof. Vladimir Tsukruk, MSE

Prof. Ravi Kane, ChBE

Craig Nies, Ph.D., AVX Corporation

Abstract:

Currently, diagnosis for serological diseases such as Ebola, HIV, and Lyme disease relies on Enzyme-linked Immunosorbent Assays (ELISAs), which require centralized laboratories and several-day timescales to complete. However, emerging technologies such as potentiometric and electrochemical impedance biosensing can be developed into portable, label-free, point-of-care devices that require only hour timescales. Specifically, potentiometric sensing platforms can be miniaturized through cost-effective microfabrication, lend themselves to multiplexed and parallel sensing, and are easily integrated with other electronics

Despite the promise of these new technologies, device reliability inhibits commercialization and adoption.  This work focuses on improving potentiometric sensing through three main aims focused on understanding erroneous behavior at the senor-solution interface. First of all, although commonly used to functionalize the sensing surface, carboxyl-terminated thiol self-assembled monolayers (COOH-SAMs) can have large defect densities, which in turn leads to large non-selective adsorption (NSA) of proteins to hydrophobic surfaces exposed by these defects. A procedure is developed where the surface of COOH-SAMs is treated before functionalization to improve the reliability and quality of receptor attachment to the sensor surface. In this method, a preblocking protein orthogonal to the immunological system of interest is used to cover hydrophobic, non-selective sites on the sensor surface while still leaving carboxylic acid headgroups available for covalent functionalization.

Secondly, COOH-SAMs oxidize when exposed to ambient conditions. The rate of this oxidation and methods to block oxidation and extend COOH-SAM lifetime will be explored. Specifically, protein preblocking will also be investigated as a barrier to oxidation.  Finally, there has been significant interest in applications of 2D materials for potentiometric sensing as well as other biomedical areas. The inert basal plane of these materials such as graphene could lead to larger biosensing signals due to a decrease in surface pH response. However, here is conflicting literature on to what extent interaction from the substrate are transmitted through a 2D monolayer, and the subsequent effect on biomolecule interactions are unknown.  Therefore, the degree to which the substrate influences 2D-protein interactions in both polar and non-polar 2D materials will be explored.