Thesis

Development of a dual-imaging platform for the analysis of nanoparticle assemblies in suspension and bioaffinity interactions

Creator
Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18035
Person Identifier (Local)
  • 202186196
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Bioaffinity sensors underpin many healthcare and diagnostic technologies, enabling the detection of disease biomarkers, therapeutic agents and other molecular species. Their application spans from point-of-care diagnostics to advanced laboratory instrumentation, supporting clinical monitoring, early disease detection and targeted drug delivery. Despite this widespread utility, current platforms remain limited in analytical performance. Conventional immunoassays often lack the sensitivity to detect low-abundance biomarkers, despite their clinical relevance at trace concentrations. Most analytical platforms also operate within fixed and narrow dynamic ranges, preventing accurate quantification across several orders of magnitude. In addition, ensemble-based measurements mask individual binding events that underlie biomolecular recognition, while multiplexing capabilities remain restricted, limiting simultaneous detection of multiple biomarkers in a single assay. Nanoparticle-enhanced biosensors have emerged as versatile tools to address these challenges, offering strong optical signals, tuneable surface chemistry and compatibility with diverse assay formats. Nanoparticle-based sensing approaches typically involve either bulk solution analysis of nanoparticle aggregation, which is spectrograph-based, or focuses on single-camera (and single modal) imaging of nanoparticle adsorption on a sensor surface. Between these two configurations, there has been very little research on the dynamic imaging of nanoparticle assemblies in suspension and developing this capability for real-time bioaffinity sensing. In this thesis, the overall aim was to develop and apply a dual-modal imaging platform for higher throughput, real-time imaging and tracking of discrete nanoparticle assemblies in suspension. This is supported by demonstrating the development of a nanoparticle assembly whose design and optimization directly benefits from these new measurement capabilities and also demonstrating the advantages of working flexibly between combinations of Rayleigh / fluorescence and dual-colour fluorescence for both assembly characterization and as an approach for higher throughput single target bioaffinity detection. A nanoparticle design for multimodal imaging was developed which involved the coassembly of gold nanorods (AuNRs) and quantum dots (QDs). A robust approach for the preparation of these optically bright nanotags was developed involving a layer-bylayer surface modification approach using polyelectrolytes and poly(tannic acid) to produce biocompatible and stable AuNR-QD nanoassemblies suitable for subsequent bioconjugation. Both AuNR-QDs and individual QDs were systematically characterized using complementary bulk and single-nanoparticle methods to confirm colloidal stability and discrete assemblies. In particular, correlated Rayleigh scattering and fluorescence dynamic dual imaging was demonstrated for these assemblies to highlight the utility of the dual imaging platform. The functionality of AuNR-QDs was demonstrated in static sandwich assays with C-reactive protein (CRP), a clinically relevant inflammatory biomarker, which confirmed their potential for integration into single-and dual-colour assay formats using both individual and combined nanostructures. A major focus of the project was the design and optimization of a platform for the dualmodal imaging of suspended nanoparticles. System requirements were established to support simultaneous multimodal detection, including precise camera alignment, calibration, optimized optics and tailored filter combinations to minimize spectral overlap. Acquisition parameters were tuned for correlated modalities, while microfluidic designs were tested to address focal depth differences between scattering and fluorescence. Proof-of-concept dual-colour assays based on streptavidin-biotin interactions further demonstrated correlated imaging of discrete assemblies and optimized system design. Automated analysis pipelines were developed to support high-throughput, quantitative tracking of dual-colour assemblies in suspension. Following on from dual-modal correlated Rayleigh scattering and fluorescence dynamic imaging of AuNR-QD assemblies in suspension, the system was subsequently applied to dual-colour CRP assays, integrating biofunctionalized AuNRQDs and individual QDs of different emission colours. The formation of discrete dualcolour nanoassemblies was successfully demonstrated both in buffer and serum, validating highly sensitive and specific detection under physiologically relevant conditions. By combining nanoparticle engineering, systematic nanoparticle characterization and comprehensive optical system development, this work establishes the basis for high-throughput single target bioaffinity sensing. It eliminates ensemble averaging through single-particle counting while extending the dynamic range and enabling multiplex detection at the single-particle level. These advances provide a foundation for ultrasensitive and clinically adaptable biosensing platforms with strong potential for early disease detection and diagnostic applications.
Advisor / supervisor
  • Wark, Alastair W.
Resource Type
DOI
Embargo Note
  • This thesis is restricted to Strathclyde users only until 30th May 2031.

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