Biosensing with Graphene-Enhanced Raman Scattering
Open Access
- Author:
- Silver, Alex
- Graduate Program:
- Electrical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 23, 2020
- Committee Members:
- Shengxi Huang, Thesis Advisor/Co-Advisor
Zhiwen Liu, Committee Member
Kultegin Aydin, Program Head/Chair - Keywords:
- biosensing
graphene
raman spectroscopy
SERS
GERS
sensing - Abstract:
- Biosensing is critical for health monitoring and disease diagnosis, yet most current biosensing methods require the use of sophisticated processing to provide effective analysis. Surface-enhanced Raman spectroscopy is rapid, label-free, and combines spectral fingerprinting with excellent sensitivity, but its use in biosensing has been hampered via its traditional medium of roughened metal surfaces, which introduces a lack of reproducibility and biocompatibility. Graphene, a two-dimensional material consisting of sp2 hybridized carbon atoms, provides an alternative that is highly reproducible, with the added advantages of facile processing and good biocompatibility. However, the mechanism of graphene-enhanced Raman scattering (or GERS) is complex, and it remains challenging to predict whether complex biomolecules such as proteins will satisfy the conditions required for GERS. Therefore, this study seeks to elucidate the interactions of biomolecules on graphene, first using hemoglobin to investigate the GERS mechanism, and then applying that knowledge to probe the structure and ligand-binding of a critical cellular surface receptor. Building on previous work, hemoglobin was studied and found to have selective enhancement, with a maximum enhancement factor of 9.97. Hemoglobin enhancement was also dependent on factors such as the analyte concentration, and the number of graphene layers. G-protein coupled receptor CXCR4, a component of cellular membranes which regulates many important biological functions, was observed in the process of binding to ligands via charge transfer effects. For the first time in literature, spectra of CXCR4 and associated ligands CXCL12 and CCL5 were collected. It is hoped that this work will lead to a more complete understanding of GERS, and also provide a novel method for observing the electronic structure of large proteins involved in crucial biological processes.