Document Type
Dissertation
Date of Award
12-31-2021
Degree Name
Doctor of Philosophy in Chemistry - (Ph.D.)
Department
Chemistry and Environmental Science
First Advisor
Kevin D. Belfield
Second Advisor
Hao Chen
Third Advisor
Buyang Kim
Fourth Advisor
Yuanwei Zhang
Fifth Advisor
Xuan Liu
Abstract
Fluorescent probes are a vital tool in the study of cell imaging. There are many types of fluorescent probes ranging from inorganic and organic nanoparticles to organic molecules. When used judiciously, they can help provide essential information on cellular structure and function. The introduction of two-photon microscopy has expanded the need for new probes, in particular near-infrared (NIR) absorbing and emitting fluorescent probes. The photochemical and photophysical properties of NIR probes play a crucial role in their effectiveness in cell imaging by both conventional and two-photon excitation (2PE) microscopy. In this research, the synthesis, photophysical properties, and two-photon absorption (2PA) properties of two very different classes of NIR fluorescent probes are explored.
In the first type of fluorescent probe, inorganic nanoparticles, oleic acid (OA) functionalized bismuth nanoparticles are synthesized to investigate their potential use as a NIR probe for multiphoton imaging. The bismuth nanoparticles are investigated due to their low cellular toxicity and relative abundance if Bi. The OA-Bi nanoparticles two-photon absorption properties are measured, which has not been previously reported. The second fluorescent probe type that are explored are specific squaraine derivatives, i.e., organic molecules. Azetidyl-functionalized squaraines are synthesized as part of a strategy to create long wavelength absorbing and emitting probes with high fluorescence quantum yields and improved photophysical properties. The rigidity of the phenol azetidine is hypothesized to improve the brightness and stability of the squaraine, while maintaining necessary photophysical properties and biocompatibility. The squaraines exhibit emission in the NIR range, which posits them as potentially effective probes for 2PE microscopy.
In a hybrid of nanoparticles and organic molecule probes, micelle-forming quaternary ammonium amphiphiles referred to as Quatsomes (QSs) are evaluated as an organic nanoparticle platform to encapsulate two carbocyanine fluorescent dyes. These are selected to demonstrate Forster resonance energy transfer (FRET), which is a strategy to allow excitation at one wavelength and observe emission at significantly longer wavelengths, an aspect that can be useful to discern between the probe's fluorescence and autofluorescence from cells in biological tissue. The QSs display high degrees of stability and FRET efficiency. In vitro studies show successful cell penetration, relatively low toxicity, and high colocalization in lysosomes.
Recommended Citation
Uddin, Mehrun Nahar, "Fluorescence probes for bioimaging: synthesis, photophysical properties and applications" (2021). Dissertations. 1792.
https://digitalcommons.njit.edu/dissertations/1792
