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%0 Thesis
%A Zhang, Rui
%T Engineering gold nanoconstructs for photoacoustic imaging
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Dissertation
%C Aachen
%M RWTH-2026-01044
%P 1 Online-Ressource : Illustrationen
%D 2026
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2026
%Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2026, Kumulative Dissertation
%X Anisotropic gold nanoparticles possessing unique optical properties and different surface curvature, have emerged as attractive nanostructures in recent decades. Among them, gold nanostars (AuNS) are of particular interest since they hold distinct localized surface plasmon (LSP) resonances, yielding strong light extinction and photothermal conversion efficiencies. Their LSP bands can be centered in the near-infrared (NIR) region of the spectrum, where light penetrates deeper in tissues, by adjusting the AuNS morphology, such as branch number and aspect ratio. Thereby, AuNS have been explored as optical diagnostic and therapeutic agents for photoacoustic (PA) imaging and photothermal therapy. However, the growth of anisotropic gold nanoparticles often relies on cytotoxic shape-directing agents, such as cetyltrimethylammonium bromide (CTAB), raising safety concerns. Furthermore, those reagents tend to strongly bind to the nanoparticle surface, hindering further surface functionalization and limiting their biomedical applications. In recent years, alternative shape-directing agents, such as Good’s buffers, have been explored to overcome these problems. Good’s buffers are biocompatible and widely used in cell and tissue cultures. Moreover, they can reduce gold salts to metallic gold and promote star-shaped nanoparticle growth in absence of pre-synthesized seeds. This approach is relatively simple, nevertheless, variations in the precursor concentrations (Au3+ and Good’s buffers), pH, temperature, and agitation (stirring or vortex) can largely influence the AuNS growth, leading to high polydispersity and batch-to-batch variability. Hence, in my first study, I assessed the impact of experimental factors’ first- and second-order interactions on the seedless growth of HEPES-mediated AuNS through a fractional factorial design of experiments. My findings explain inconsistencies in previous literature and highlight that simultaneous changes of two factors (secondary interactions) can cause greater effects than the sum of individual factor changes. Additionally, Good’s buffers-mediated AuNS display the key features desired for PA imaging, including strong NIR extinctions and large photothermal conversion efficiencies. Nevertheless, no systematic study had explored the construction of PA imaging probes with Good’s buffer-mediated AuNS. In my second study, I engineered the structure of AuNS by functionalizing them with (pre-)clinical polymers and explored their performance as PA probes in vitro and ex vivo. This study highlights the potential of gold nanoconstructs as PA probes and brings new insights into rational designs of nanoagents for diagnostic applications. Beyond these two main studies, my PhD research also focused on: 1. Investigating the AuNS resilience to thermal deformation by monitoring their reshaping dynamics with environmental transmission electron microscopy (TEM). By tracking the thermal reshaping of Good’s buffers (HEPES, EPPS, and MOPS)-mediated AuNS under in-situ heating TEM, we revealed and compared the deformation behaviors of the three AuNS under local (photo-)thermal conditions, as those obtained in photoacoustic and photothermal applications. This study characterized the response of individual nanoparticles to changes in the local environment and paved our way to improve the thermal stability of gold nanoconstructs. 2. Developing silver nanostructures (spheres, plates, and cubes) for PA imaging, expanding their applications beyond most common uses, such as antimicrobial and wound healing. This study demonstrated the capabilities of (anisotropic) silver nanoparticles, including a few therapeutic formulations being investigated in clinical trials, as PA imaging agents, which may offer new opportunities in image-guided therapy.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2026-01044
%U https://publications.rwth-aachen.de/record/1026897