Hydrophilic surface modification of upconversion nanoparticles for LRET-based DNA assays

Zhou, Yingzhu

Hydrophilic surface modification of upconversion nanoparticles for LRET-based DNA assays

Zhou, Yingzhu

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Publication Type:: Thesis
Issue Date:: 2018

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Field	Value	Language
dc.contributor.author	Zhou, Yingzhu
dc.date.accessioned	2019-01-09T21:43:52Z
dc.date.available	2019-01-09T21:43:52Z
dc.date.issued	2018
dc.identifier.uri	http://hdl.handle.net/10453/129401
dc.description	University of Technology Sydney. Faculty of Science.	en_AU
dc.description.abstract	Upconversion nanoparticles (UCNPs) are emerging as a new-generation optical nanomaterial that has drawn tremendous research interests. UCNPs can sequentially absorb two or more lower-energy photons in near-infrared (NIR) range to emit one higher energy photon, typically in the visible and ultraviolet range. This anti-Stokes’ property offers a great deal of opportunities in biological and analytical applications, because NIR excites negligible amount of autofluorescence background in visible range that is an issue in conventional methods using UV or visible excitation. Furthermore, UCNPs are biocompatible, resistant to photobleaching and photoblinking, tunable in size, morphology, and composition. All these characteristics offer their potentials in diverse applications, including bioassays, chemical detections, bio-imaging, single-molecule tracking, thermometers, security inks, and photothermal therapy etc. UCNPs are used in aqueous suspension, in particular, biomedical and analytical applications for targets recognition and detection, which requires a hydrophilic surface. However, UCNPs are synthesised in the organic solvent with the inherent hydrophobic surface. The key is to modify their surface from being hydrophobic into hydrophilic. Among a series of surface modification strategies, ligand exchange stands out because of its simplicity, and versatility for further conjugations with functional groups. This thesis focuses on a systematic study of the hydrophilic surface modification methods to identify a one-step ligand exchange strategy for UCNPs. Based on this study, development of a robust homogenous assay, based on Luminescence Resonance Energy Transfer (LRET), is also demonstrated to achieve detection of DNA disease biomarkers. In this thesis, Chapter I covers the objectives, structure and organization; Chapter II gives the detailed literature review and the introduction of UCNPs; followed by Chapter III, a systematical evaluation of the performance of four common polymers in transferring the surface of UCNPs from being hydrophobic to hydrophilic. Chapter IV reports the development of a platform for DNA detection in homogeneous solutions based on LRET, which work has been published as a peer-reviewed article.	en_AU
dc.format	Thesis (MSc)
dc.language.iso	en_AU	en_AU
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/129401/2/02whole.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	au.edu.uts.lib/ppc
dc.subject	upconversion nanoparticles
dc.subject	UCNPs
dc.subject	surface modification
dc.subject	ligand exchange
dc.subject	ligand substitution
dc.subject	Luminescence Resonance Energy Transfer
dc.subject	LRET
dc.title	Hydrophilic surface modification of upconversion nanoparticles for LRET-based DNA assays	en_AU
dc.type	Thesis	en_AU
utslib.copyright.status	open_access

Abstract:

Upconversion nanoparticles (UCNPs) are emerging as a new-generation optical nanomaterial that has drawn tremendous research interests. UCNPs can sequentially absorb two or more lower-energy photons in near-infrared (NIR) range to emit one higher energy photon, typically in the visible and ultraviolet range. This anti-Stokes’ property offers a great deal of opportunities in biological and analytical applications, because NIR excites negligible amount of autofluorescence background in visible range that is an issue in conventional methods using UV or visible excitation. Furthermore, UCNPs are biocompatible, resistant to photobleaching and photoblinking, tunable in size, morphology, and composition. All these characteristics offer their potentials in diverse applications, including bioassays, chemical detections, bio-imaging, single-molecule tracking, thermometers, security inks, and photothermal therapy etc. UCNPs are used in aqueous suspension, in particular, biomedical and analytical applications for targets recognition and detection, which requires a hydrophilic surface. However, UCNPs are synthesised in the organic solvent with the inherent hydrophobic surface. The key is to modify their surface from being hydrophobic into hydrophilic. Among a series of surface modification strategies, ligand exchange stands out because of its simplicity, and versatility for further conjugations with functional groups. This thesis focuses on a systematic study of the hydrophilic surface modification methods to identify a one-step ligand exchange strategy for UCNPs. Based on this study, development of a robust homogenous assay, based on Luminescence Resonance Energy Transfer (LRET), is also demonstrated to achieve detection of DNA disease biomarkers. In this thesis, Chapter I covers the objectives, structure and organization; Chapter II gives the detailed literature review and the introduction of UCNPs; followed by Chapter III, a systematical evaluation of the performance of four common polymers in transferring the surface of UCNPs from being hydrophobic to hydrophilic. Chapter IV reports the development of a platform for DNA detection in homogeneous solutions based on LRET, which work has been published as a peer-reviewed article.

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