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Synthesis and Characterization of Near-Infrared (nir) Emissive Conjugated Polymer Dots for Tumoroid Imaging
(01. Izmir Institute of Technology, 2024) Karabacak, Soner; Yıldız, Ümit Hakan
This thesis describes the synthesis and characterization of near-infrared (NIR) emissive conjugated polymers and their polymer dots (Pdots). The Pdots were exploited to image the tumor cells and tumor spheroids. The penetration behavior of NIR emissive Pdots was characterized in five different tumor spheroid models. Three different polymerization techniques were tried to synthesize the NIR emissive polymers, namely oxidative, direct arylation, and Stille polymerization. The obtained NIR emissive polymers underwent structural and optical characterization. P1 was chosen as a model polymer to obtain Pdots from NIR emissive polymers for imaging tumoroids. Pdot preparation includes using ultrasonic emulsification to modify nonionic D-A-D type alkoxy thiophene-benzobisthiadiazole-based conjugated polymers (P1) with amphiphilic cetyltrimethylammonium bromide (CTAB). The technique yields Pdots with a significant positive surface charge of +56.5 mV ± 9.5 and an average hydrodynamic radius of 12 nm. Optical characterization reveals that these Pdots were found as emissive in the NIR region, with a maximum wavelength of 860 nm. These Pdots possess colloidal and optical properties that make them appropriate for use as fluorescence emissive probes in bioimaging applications. The advantageous use of positively charged Pdots has been proven in diffusion-limited settings such as tissues, specifically in certain tumor spheroid models produced from the tumoroid cell lines. After the fluorescence imaging analysis, the Pdots' emission intensity profile indicates that they have high penetration capability into the tumoroid models' center parts. The results show that Pdots with a single-chain donor-acceptor polymer structure that has been cationized with CTAB can penetrate through dense materials over about 1 μm. This provides valuable insights into the progression of targeted theranostic strategies in cancer therapy.
Characterization of Conjugated Polyelectrolytes for Nucleic Acid Sensing, Gene Delivery and Imaging
(01. Izmir Institute of Technology, 2022) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan
In this thesis, cationic derivatives of poly(3-alkylmethoxythiophene) (PT) which are a class of conjugated polyelectrolytes (CPE), have been synthesized. PT has been polymerized via FeCl3 oxidative polymerization, were treated in a set of solvents to elaborate coil conformation of polymer chain in different physicochemical environment. Spectroscopic and scattering techniques have ascertained that ethylene glycol is a good solvent for PT regarding Flory-Huggins theory. The smaller interaction parameter of PT with respect to ethylene glycol than water drives a thermodynamically driven ultra-small particle (Pdot) formation in aqueous phase by a rapid nanophase separation between PTrich ethylene glycol and PT-poor water phase. All CPEs have been then employed to prepare single polymer chain polymer dots (Pdot) by “nanophase separation” method. As a next step, Pdots have been characterized in terms of optical and colloidal properties that they possess in the backbone conformations altered by solvation effect. Regarding their colloidal characteristic, translocation of Pdot into cancerous cells was analyzed compared to healthy cells by 2D cell culture and co-culture studies. It has reported that Pdots have ability to penetrate through nuclear envelope in hepatocellular carcinoma whereas accumulate around nucleus of healthy liver cells in cytoplasm. Additionally, Pdots were studied in breast cancer cell lines to understand the behavior of Pdot staining in 2D cell culture of invasive and non-invasive breast cancer types. The findings suggest that Pdots are prone to penetrate into the invasive cancerous cells attributed to the greater deformations on nucleus membrane of triple negative breast cancer cells. In a next application, the enhanced photophysical property of PT exhibited in ethylene glycol media allows PT to be utilized as a fluorescent probe for determination of single nucleotide polymorphism by a non-amplification-based protocol. Fluorescence emission at specific wavelengths resulted from very distinct conformations of PT chain is the key elements for the SNP detection assay. The evaluation of optical data obtained from the probe with principal component analysis proves the separation of healthy individuals from patients with an overall 96% accuracy.

Phd Degree / Doktora

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