Functionalisation of gold nanoparticles to detect a protein expressed in E. coli using Raman spectroscopy: a proof of concept

Details

Supervisors

Hermans, Sophie ; Gillis, Annika

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques, à finalité approfondie

Abstract

This Master dissertation addresses the growing issue of bacterial infections, increasing antimicrobial resistance, and the need to optimise and enhance the sensitivity of pathogen detection methods. The study focuses on developing a new sensor for Surface Enhanced Raman Spectroscopy (SERS) to detect bacterial pathogens in their lysate. The SERS sensor consists of gold nanoparticles functionalised with an antibody specific to a green fluorescent protein (GFP), namely a recombinant protein expressed by E. coli. Gold nanoparticles enhance Raman spectroscopy signals through a phenomenon called localised surface plasmon resonance. The methodology involved synthesising three shapes of gold nanoparticles: namely rods, spheres, and stars. These nanoparticles were then labelled with a Raman reporter as an internal standard. They were then characterised using techniques such as UV-visible spectroscopy, transmission electron microscopy, and Raman spectroscopy. Then, functionalisation was achieved through a silica coating that allows the attachment of the antibody after its grafting with a coupling agent. The silica coating not only facilitates the functionalisation of the nanoparticles but also provides protection and stability of the nanoparticles in suspension. The results indicated that coated nanostars exhibit significantly enhanced Raman signal intensity of the Raman reporter due to their anisotropic morphology. The GFP was expressed after induction of the E. coli strain, confirmed by SDSPAGE and fluorescence microscopy. Bacterial lysis was successfully achieved using lysozyme, also confirmed by fluorescence microscopy. Finally, the SERS sensor was successfully developed to detect the GFP in the lysate of E. coli. Unfortunately, it cannot be stated with certainty that GFP was detected using the new SERS sensor, but the signal of the reporter was not lost. The conclusion of this work highlights the potential impact of this technology in the medical field and the prospects for future research aimed at further improving this sensor.