Thesis

Development of functionalised nanoparticles for cancer imaging using Surface-Enhanced Spatially Offset Raman Spectroscopy (SESORS)

Creator
Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2024
Thesis identifier
  • T16968
Person Identifier (Local)
  • 201985503
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Nanoparticles (NPs) have become increasingly important in medical diagnostics and as therapy agents. This is particularly relevant in the field of cancer nanotheranostics since cancer is the second highest cause of mortality worldwide after cardiovascular disease. The aim of this research was the preparation of NPs possessing high biocompatibility, intense surface enhanced Raman scattering (SERS) signals and excellent targeting ability to be used as imaging agents with surface-enhanced spatially offset Raman spectroscopy (SESORS). Tailoring NP synthesis for the intended application is key to maximising their targeting and sensing capabilities, therefore several NP types were investigated. Spherical large Au NPs were prepared through seed-mediated growth to exploit the enhanced scattering of larger Au NPs and were coated with silica to form biocompatible single-core shell-isolated NPs (SHINs). Raman reporter induced aggregates of seed-mediated Au NPs were also stabilised through shelling with silica. Anisotropic gold nanostars (Au NSs) and more biocompatible silica coated Au NSs (AuNS@SiO2) were also prepared. The SERS performance of the different Au NP morphologies using 785 nm laser excitation was compared whilst maintaining a NP diameter <100 nm to enable efficient cellular uptake. The results of this study confirmed that silica coated aggregates of seed-mediated Au NPs, benefitting from a secondary plasmon in the NIR perform the best using 785 nm laser excitation, whilst anisotropic Au NSs perform the worst. The different nanotag morphologies comprising spherical “bare” Au NPs, single- and multi-core SHINs and anisotropic AuNS@SiO2 were then detected through a tissue mimic consisting of 40 mm of lean porcine tissue using a handheld SORS spectrometer with a NIR laser excitation source (830 nm). This study aimed to determine the relationship between nanotag morphology, surface coating and optical properties with performance as through-tissue scatterers for SESORS imaging. The results of this study showed that silica coated aggregates performed the best indicating that the presence of hot spots in the prepared nanotags improved through-tissue imaging. The SERS signal from the three spherical core nanotags could be observed by eye through 40 mm of tissue at a low nanotag concentration, with principal component analysis indicating that greater depths of 50 mm could be probed with these nanotags. This indicated that the tailored spherical core nanotags hold potential as bright through-tissue imaging agents in combination with SESORS. The final focus of this thesis was on the preparation of antibody-conjugated, shell-isolated nanotags designed to specifically and selectively target two upregulated biomarkers associated with distinct breast cancer phenotypes. Single-core SHINs were bioconjugated to anti-oestrogen receptor-alpha (ERα) and anti-human epidermal growth factor 2 (HER2) antibodies to target ERα and HER2 positive breast cancer cells. 3D SERS microscopy coupled with conventional 3D Raman mapping was used to track the cellular localisation of the nanotags in 2D cell cultures over a period of 16 hours to determine the time dependence of nanotag uptake. 3D SERS mapping was used to identify nanotag location within the 3D volume of a cell in combination with conventional Raman mapping to detect the intrinsic cellular signal, thereby providing unequivocal verification of nanotag uptake within the cell volume or at the cell membrane. The study showed that anti-ERα nanotags preferentially accumulated in the cytoplasm of ERα(+) MCF-7 cells after 8 hours, with minimal non-specific uptake, whilst anti-HER2 nanotags showed binding to overexpressed membrane-bound HER2 in HER2(+) SK-BR-3 cells after 1 hour. 3D SERS and conventional Raman mapping were also used to determine if the nanotags had potential to be applied as a multiplex to determine breast cancer cell phenotype. 2D cell cultures consisting of MCF-7 and SK-BR-3 cells were treated either with a single-plex or a duplex of the antibody-conjugated nanotags. Each nanotag type was functionalised with either 4-(1H-pyrazol-4-yl)pyridine (PPY) or 1,2-bis(4-pyridyl)ethylene (BPE) enabling each nanotag location to be determined even when co-localised. 3D SERS mapping in mixed cell cultures showed that the anti-ERα nanotags had high specificity and selectivity for MCF-7 cells, with very low accumulation in ERα(–) SK-BR-3 cells, whilst the anti-HER2 nanotags accumulated preferentially at the cell membrane of SK-BR-3 cells, where HER2 is overexpressed. This study further highlighted the excellent targeting effects of the nanotags and the amenability of SERS as a combined imaging and phenotyping tool. This thesis highlights how targeted antibody-conjugated nanotags, tailored to give bright SERS signals with NIR laser excitation have the potential to be used as combined breast cancer phenotyping and imaging agents using SERS microscopy. Furthermore, this work also showcased the through-tissue performance of the nanotags, indicating the amenability of the nanotags to be applied in SESORS.
Advisor / supervisor
  • Graham, Duncan (Professor of Chemistry)
  • Faulds, Karen
Resource Type
Note
  • This thesis was previously held under moratorium from 7th June 2024 until 7th June 2026.
DOI
Date Created
  • 2023
Embargo Note
  • The digital copy of this thesis is restricted to Strathclyde users only until 7th June 2029.

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