Date of Graduation

5-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science & Engineering (PhD)

Degree Level

Graduate

Department

Materials Science & Engineering

Advisor/Mentor

Li, Jiali

Committee Member

Singh, Surendra P.

Second Committee Member

Chen, Zhong

Third Committee Member

McNabb, David S.

Fourth Committee Member

Wise, Rick L.

Keywords

Amyloid Beta; Beta lactoglobulin; Nanopore; Protein Aggregation; Tau; Tubulin

Abstract

Protein aggregation has been linked to many chronic and devastating neurodegenerative human diseases and is also strongly associated with aging. In the case of neurodegenerative diseases, α, β tubulins and tau proteins dissociate in a neuron cell and aggregate both intra and extra-cellularly. Tau and tubulin aggregations were found as one of the major causes of many neurodegenerative diseases, such as Parkinson’s, Picks, Alzheimer’s, Huntington, and Prion. Finding the state and mechanism of protein aggregation is significant. In this work, tau and tubulin aggregations were detected in ionic solutions using the solid-state nanopore technique. Besides tau and tubulin, aggregations of β-lactoglobulin were characterized using solid-state nanopore to understand amyloid plaques formation in Alzheimer’s disease. The nanopores (6-30 nm in diameter) were fabricated in a silicon nitride membrane on a silicon substrate by combination of focused ion beam milling and ion beam sculpting. Protein molecules were driven through nanopores by applied voltages (60-210 mV) in ionic solution (0.1M – 2M KCl). A protein molecule passing through a pore will partially block ionic current flow through the nanopore due to an increase in pore resistance which generates a current drop event that can be recorded. The amplitudes of ionic current drops were proportional to the excluded volume of protein molecules. Protein aggregations were detected by comparing the current blockage signals of monomer and aggregated proteins. Results of this research showed that solid-state nanopores were highly sensitive in the detection of dimeric to heptameric aggregations in ionic solutions at different pH salt concentrations, and voltages. Protein aggregations measured using AFM scanning were consistent with nanopore results.

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