Uncovering molecular orientation and morphology at biotic/abiotic interface for peptide-based graphene sensors

The functionality of biosensors is dictated by the biointerface formed by the bioreceptor attached to a transducer material. Among other factors, the conformation of the bioreceptor before and after analyte recognition and binding can be crucial to determining the success of the biosensor application. Therefore, it is imperative to understand the dynamics of changes in the bioreceptors’ orientation for a better biointerface design. In this thesis, we aimed to uncover the mechanisms behind the sensing performance of peptide-functionalized carbon-based biosensors developed for sensing volatile organic compounds (VOCs). Using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) as the primary investigation tool, atomic-level information was obtained about the orientation of the peptide backbones in relation to the graphene surface upon the VOC binding. At the same time, changes in morphology were assessed through atomic force microscopy (AFM). The results showed that almost all designed peptides tend to adopt an overall parallel orientation on the graphene surface, and the presence of aromatic residues reduces peptide backbone alignment. Moreover, exposure to the VOCs caused distinct changes in the peptide’s orientation that were not correlated to the sensing performance, which seems to be dictated by the displacement of the peptide backbones from the graphene surface. Peptide sequences with more aromatic residues usually showed higher sensing performance. Therefore, the primary sensing mechanism is more related to changes in the charge transfer between the peptide aromatic side chains and the graphene electronic structure due to VOC disruption than to peptide-specific binding to the VOC molecules. These results are presented in such a way that they can increase the knowledge about peptide/carbon-based biointerfaces, leading to the development of more accurate, reliable and sensitive peptide-functionalized carbon-based biosensors.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2025

Author dc:creator

• Sant'Anna, Gustavo

• biosensor
• peptide
• graphene
• nexafs
• afm
• anzsrc-for: 4004 Chemical engineering

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/31009

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/104584