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Bio/chemical sensing and generation of reactive oxygen species based on upconverting nanoparticles.

Jesu Raj, Joe Gerald (2017). Bio/chemical sensing and generation of reactive oxygen species based on upconverting nanoparticles. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 168 p.

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The intention of this thesis is to explore new applications of hybrid near-infrared (NIR) perturbable lanthanide (Ln3+) upconverting nanoparticles (UCNPs) in the fields of DNA biosensing and copper ion (Cu2+) chemical sensing. Furthermore, the use of these UCNPs as well as superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with an organometallic iridium (Ir) complex for the generation of reactive oxygen species (ROS), which are reactive intermediates in photodynamic therapeutic applications, is investigated. First, we investigated DNA biosensing by synthesizing Ln3+-based, UV/blue emitting, thulium (Tm3+) and ytterbium (Yb3+) co-doped NaYF4 UCNPs as the energy donor upon 980 nm NIR excitation. These UV/blue emitting UCNPs were then integrated into polymer-based nanoparticle and this polymer/upconverting nanohybrid material was appropriately functionalized with the probe DNA sequence via its amino end. In a separate synthesis monodispersed gold nanoparticles (AuNPs) and an Ir complex were prepared. The presence of two carboxyl functional groups on the Ir complex provided suitable conjugation chemistry for the covalent attachment of the complex to the surface of AuNPs through a suitable linker molecule having a thiol functional group. The other end of the probe DNA sequence possessing a thiol end was directly functionalized on the AuNPs thus forming the energy acceptor nanohybrid material. The donor UCNP/polymer nanohybrid and the acceptor AuNP/Ir nanohybrid were brought to close proximity through the helical structure formation of the probe DNA. This facilitates the energy transfer between the Tm3+/Yb3+ co-doped UCNPs and the Ir complex functionalized AuNPs. Subsequent addition of target DNA sequence resulted in the DNA hybridization and elongation thus increasing the distance between the donor and acceptor species. Since this energy transfer is distance dependent, a highly sensitive and selective DNA nanosensor was developed that is sensitive to picomolar concentration of target DNA and highly selective up to a single base mismatch. Optical nanosensors based on the Tm3+/Yb3+ doping pair in a different upconverting host crystal such as LiYF4 offers many advantages. In contrast to the NaYF4 host matrix, LiYF4 offers more intense NIR to UV/blue upconversion. These optical features of LiYF4 thus enable the designing of multifunctional nanoplatforms based on LiYF4 UCNPs with combined dual-mode (that is, upconversion and conventional luminescence) detection. In another part of this thesis, we have integrated a naturally occurring, medicinally important organic compound, curcumin, in combination with the Tm3+/Yb3+ co-doped LiYF4 UCNPs. This NIR perturbable organic/inorganic nanohybrid material has been successfully used as a chemical sensor for the detection of Cu2+ ions and showed high sensitivity, selectivity, biocompatibility and excellent Stern-Volmer features. Energy transfer has been achieved between the donor UCNPs and the locally decorated curcumin as an acceptor or reporter molecule. The energy transfer has been a key feature in sensing of Cu2+and was achieved by careful synthesis of UV/visible and NIR emitting LiYF4:Tm3+/Yb3+ co-doped UCNPs followed by coating of a thin layer of silica (SiO2) in order to render them water dispersible. These SiO2 coated UCNPs act as suitable donor material when functionalized with highly biocompatible curcumin leading to the formation of the inorganic/organic nanohybrid, which has been proven to be an excellent material for sensing of Cu2+ ions with high selectivity. The detection limit of this nanohybrid has been found to be 4.75 nM, which is far lower than the allowed Cu2+ limit for drinking water allowed by the United States Environmental Protection Agency (USEPA). This curcumin tagged nanohybrid material also showed a robust selectivity towards Cu2+ ion even in the presence of other metal ions including heavy metals. Another section of this thesis deals with the synthesis of monodispersed LiYF4:Tm3+, Yb3+@SiO2 UCNPs and their functionalization with varying concentrations of the Ir complex, used in the DNA sensing chapter 3 of this thesis, on their surface. The photophysical properties of these LiYF4:Tm3+,Yb3+@SiO2-Ir nanostructures were investigated and it was demonstrated that upon surface functionalization with the Ir complex, a complete quenching of the upconverted UV emission from the Tm3+ ions was observed. Following absorption of the upconverted UV light, the Ir complex demonstrated a capacity to generate ROS, which was measured in the presence of a probe molecule 1,3-Diphenylisobenzofuran (DPBF). Spectroscopic studies of the upconversion luminescence showed that the photosensitization of the Ir complex was radiative in nature. To confirm that the generation of ROS was in fact due to photosensitization of the Ir complex from the UCNPs, two control experiments were also carried out. First, LiYF4:Tm3+,Yb3+@SiO2 UCNPs alone (without the Ir complex) were studied to observe if the upconverted UV light itself was capable of generating ROS. Second, the Ir complex alone was studied following excitation at 980 nm. In both cases, no ROS was observed indicating that both the UCNPs and the Ir complex are required to generate ROS. This newly developed LiYF4:Tm3+,Yb3+@SiO2-Ir nanoplatform lays the foundation for the NIR triggered generation of ROS, which effectively eliminates the need for low penetrating, high energy external UV excitation, normally required for such photosensitizers. In addition we have synthesized and integrated a multi-modal nanoprobe that consists of an Ir complex functionalized on the surface of SiO2 coated SPIONs. This particular nanohybrid offers generation of ROS under direct UV illumination, however, it allows for the possibility of exploiting the paramagnetic component of the system for potential applications such as magnetically guided targeting and magnetic resonance imaging. The production of ROS is vital in applications with regard to surface oncology. Since the as synthesized Ir complex exhibits intense visible emission under UV excitation, this Ir complex decorated SPIONs system offers multiple applications such as imaging, and ROS generation hence could be used as a multi-modal nanoprobe.

Type de document: Thèse Thèse
Directeur de mémoire/thèse: Vetrone, Fiorenzo
Informations complémentaires: Résumé avec symboles
Mots-clés libres: nanoparticules; DNA; upconversion; biosensing; sensitive detection of ssDNA; near infrared sensing; curcumin tagged; reactive oxygen species
Centre: Centre Énergie Matériaux Télécommunications
Date de dépôt: 29 août 2017 19:02
Dernière modification: 29 août 2017 19:02
URI: http://espace.inrs.ca/id/eprint/5288

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