Biofunctionalization of upconversion nanoparticles for intracellular labeling and imaging

Asrat, Tesfaye Eshete

Biofunctionalization of upconversion nanoparticles for intracellular labeling and imaging

Asrat, Tesfaye Eshete

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Publication Type:: Thesis
Issue Date:: 2022

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Field	Value	Language
dc.contributor.author	Asrat, Tesfaye Eshete
dc.date.accessioned	2023-09-08T04:03:30Z
dc.date.available	2023-09-08T04:03:30Z
dc.date.issued	2022
dc.identifier.uri	http://hdl.handle.net/10453/172006
dc.description	University of Technology Sydney. Faculty of Science.	en_US.UTF-8
dc.description.abstract	Lanthanide-doped upconversion nanoparticles (UCNPs) are emerging as the next-generation agent for intracellular fluorescent labeling and imaging. To label the subcellular structures using UCNPs, vast opportunities and immense potential lay in their surface functionalization and subsequent bioconjugations. The surface stability and reactivity of UCNPs determine their specific interactions with target molecules, and it enables control of the degree of non-specific bindings to the surroundings. The targetability of UCNPs could be optimized by molecule-specific moiety via conjugating to the grafted polymers on the surface of nanoparticles. As the surface of UCNPs is highly positively charged, due to the exposed lanthanide ions at the lattice termination sites, the nanocrystal surfaces allow the tethering of polymers with negative charges. Therefore, the design and tethering polymers is the key factor in producing functional inorganic nanoparticles with a desirable surface property. Throughout the Ph.D. study, a new understanding of the roles of polymers in functionalizing UCNPs has been achieved by systematic investigations of multiple RAFT copolymers. RAFT copolymers play a crucial role in controlling surface features and reactivities of UCNPs by manipulating physicochemical properties. The UCNP's surface coupling efficiency could be enhanced using highly reactive triblock RAFT copolymers containing methacrylic acid (MAA). Through increasing surface carboxylic acids density and by enabling an extended surface reactive site, advances in reactivity and dispersibility of UCNPs could be achieved. The surface graft copolymer composition determines the amphiphilicity, dispersibility, and stability of UCNPs. The concept of double copolymer surface grafting using stepwise co-grafting has been implemented to attain high control of surface composition. Efficient immobilization of antibodies and peptides to UCNPs enables the targeting and imaging of single biomolecules and intracellular structures. The performed intracellular labeling and imaging experiments prove that the functionalized UCNPs are suitable for detailed intracellular labeling and investigations. This thesis, therefore, contributes to developing the next-generation super-resolution probes for single-molecule tracking and live cell imaging applications. Moreover, besides visualization of structural features and dynamics of molecular-level phenomena, the functionalized nanoparticles could be implemented as a nano-theranostic tool for personalized nanomedicine.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/172006/2/02whole.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2022 Tesfaye Eshete Asrat
dc.rights	au.edu.uts.lib/cph
dc.title	Biofunctionalization of upconversion nanoparticles for intracellular labeling and imaging	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Lanthanide-doped upconversion nanoparticles (UCNPs) are emerging as the next-generation agent for intracellular fluorescent labeling and imaging. To label the subcellular structures using UCNPs, vast opportunities and immense potential lay in their surface functionalization and subsequent bioconjugations. The surface stability and reactivity of UCNPs determine their specific interactions with target molecules, and it enables control of the degree of non-specific bindings to the surroundings. The targetability of UCNPs could be optimized by molecule-specific moiety via conjugating to the grafted polymers on the surface of nanoparticles. As the surface of UCNPs is highly positively charged, due to the exposed lanthanide ions at the lattice termination sites, the nanocrystal surfaces allow the tethering of polymers with negative charges. Therefore, the design and tethering polymers is the key factor in producing functional inorganic nanoparticles with a desirable surface property. Throughout the Ph.D. study, a new understanding of the roles of polymers in functionalizing UCNPs has been achieved by systematic investigations of multiple RAFT copolymers. RAFT copolymers play a crucial role in controlling surface features and reactivities of UCNPs by manipulating physicochemical properties. The UCNP's surface coupling efficiency could be enhanced using highly reactive triblock RAFT copolymers containing methacrylic acid (MAA). Through increasing surface carboxylic acids density and by enabling an extended surface reactive site, advances in reactivity and dispersibility of UCNPs could be achieved. The surface graft copolymer composition determines the amphiphilicity, dispersibility, and stability of UCNPs. The concept of double copolymer surface grafting using stepwise co-grafting has been implemented to attain high control of surface composition. Efficient immobilization of antibodies and peptides to UCNPs enables the targeting and imaging of single biomolecules and intracellular structures. The performed intracellular labeling and imaging experiments prove that the functionalized UCNPs are suitable for detailed intracellular labeling and investigations. This thesis, therefore, contributes to developing the next-generation super-resolution probes for single-molecule tracking and live cell imaging applications. Moreover, besides visualization of structural features and dynamics of molecular-level phenomena, the functionalized nanoparticles could be implemented as a nano-theranostic tool for personalized nanomedicine.

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