Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Biology and Chemical Technology | en_US |
| dc.creator | Mak, Ho Nam | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13646 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Design, development, and study of reaction-based luminescent and MRI probes for sensing and imaging | en_US |
| dcterms.abstract | Hydrogen sulfide (H2S) is recognized as a reactive sulfur species (RSS) and is highly toxic. It can be produced endogenously and plays a vital role in cellular processes in the human body. However, to date, most sensing probes are single-modality design, which limits their sensitivity and utility. Chapter 3 mainly focuses on synthesis and application of reaction-based fluorescence/T1-MRI dual-modality probe, NBD[Gd]-L2, for H2S imaging. NBD[Gd]-L2 provides both fluorescence and MRI signal responses in the presence of H2S. In the fluorescence response, it shows an 88.4% fluorescence quenching with a detection limit of 578 nM in 60 minutes. In biological experiments, NBD[Gd]-L2 demonstrates low cytotoxicity in a selected normal cell line (HK-2) and a cancer cell line (HeLa) and exhibits a "turn-off" property in confocal experiments when the cells are incubated with exogenous H2S. In the MRI response, the T1-weighted relaxivity (r1) value demonstrates a 36.4% reduction because of the loss of molecular weight and changes in the residual water lifetime of the Gd3+ complex. Due to the reduction in r1 value, NBD[Gd]-L2 in MR phantom experiments shows a "bright" image at the initial state and the image is "darkened" after the addition of H2S. This study provides a lanthanide-based fluorescence/MRI dual probe for the detection of H2S. | en_US |
| dcterms.abstract | Hydrazine (N2H4) is well known as a highly reactive chemical compound and has been utilized in various scientific research and industrial fields. However, it is highly toxic to the human body and has the potential to pollute the environment through industrial processes. In Chapter 4, the focus is mainly on the design, development and study of a lanthanide-based hydrazine probe, Hz[Ln]-L1. When Tb3+ ions are coordinated, Hz[Tb]-L1 exhibits a luminescence response signal for hydrazine detection. In the presence of hydrazine, Hz[Tb]-L1 demonstrates a 129-fold enhancement of the Tb luminescence in three minutes with a detection limit of 256 nM. When Gd3+ is inserted into the ligand, an obvious magnetic response is produced by Hz[Gd]-L1 in response to hydrazine. In detail, the T1-weighted relaxivity value (r1) shows a 2.7-fold enhancement, increasing from 1.5 mM-1s-1 to 4.0 mM-1s-1. Additionally, in the MRI phantom experiment, Hz[Gd]-L1 demonstrates a "dark" image in the initial state which turns "bright" after interacting with hydrazine. From the luminescence lifetime experiment and HRMS analysis, it is confirmed that the phthalimide group is removed in the presence of hydrazine, causing the hydration number of the complex to change from 0 to 1 and resulting in an r1-enhancing property. This study provides a lanthanide-based probe for hydrazine, showing a 129-fold increase in Tb luminescence and a 2.7-fold enhancement in the T1-weighted relaxivity with the coordination of Tb or Gd, respectively. | en_US |
| dcterms.abstract | Formaldehyde is also well known as an environmental toxin and carcinogen. An overload of formaldehyde can damage the central nervous system. It is important to develop selective and sensitive fluorescent probes for formaldehyde imaging. Recently, an analyte regenerating strategy for formaldehyde has been developed. The key to this strategy is enabling formaldehyde detection with no or minimum perturbation to the homeostasis of formaldehyde in biological systems. However, extra care should be taken with formaldehyde regenerating fluorescent probes due to the risk of degradation of the probe. In Chapter 5, formaldehyde regenerate fluorescent probes, Cou-NSu is designed and studied. Although Cou-NSu shows a selective response toward formaldehyde, a self-enhancing emission peak appears upon storage in a 10 mM PBS buffer solution/ 1% DMSO which could adversely affect the accuracy and reproducibility of formaldehyde detection. From the LC-MS analysis, a hydrolysate of Cou-NSu is found, confirming that Cou-NSu undergoes hydrolysis in the presence of water at neutral pH. This limits the biological application of current analyte regenerate strategy for formaldehyde detection. Of note, the hydrolysis of probe employing this strategy has not been previously observed and reported. This study provides a new formaldehyde probe designed following the analyte-regenerating strategy, pointing out the risk of hydrolysis which may negatively affect the quantification study of formaldehyde. | en_US |
| dcterms.abstract | In conclusion, four chemical probes are designed for detecting heavy metals or small molecules, that are environmentally and physiologically toxic. It is hoped that the reaction-based chemical probes described here will inspire the design of powerful chemical tools for practical applications in environmental and biomedical fields in the future. | en_US |
| dcterms.extent | 254 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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