Synthesis of time-resolved fluorescence probes for the future detection and improved study of cancer

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Alyssa Marie Frediani (Creator)
Western Carolina University (WCU )
Web Site:
Brian Dinkelmeyer

Abstract: The goal of this project is to develop a diagnostic tool for detecting melanoma cells. The design entails using a polyethylene glycol (PEG) linker to attach a luminescent lanthanide complex to a peptide (MSH-4) that specifically targets G-protein coupling receptors on melanocytes. Lanthanide chelate labels, such as europium thenoyltrifluoroacetone (Eu(TTA)3), have great potential as imaging and detection agents since their luminescent properties allow them to be visualized with high efficiency over the fluorescence of a biological background. The synthesis of each component; linker, ligand, complex and peptide was attempted. The MSH-4 protein was successfully synthesized on a Rink-amide resin using an FMOC protection/deprotecting as evidenced by positive ninhydrin tests after each coupled amino acid. The phenanthroline amine ligand was successfully synthesized as well as its europium complex made. The quantum yield for the Eu(TTA)3-5-amine-1,10-phenanthroline complex was measured and was determined to be sufficient for our purposes. However, difficulties arose in attaching the PEG linker to the phenanthroline amine ligand. The amine functional group was too poor of a nucleophile to react with an O-tosylated PEG linker. This unforeseen challenge necessitated a change in the synthetic strategy. The idea came to add a functional group with a better leaving group. This led to using bromo acetic anhydride to convert the amine to a bromo acetamide. The reaction to couple this anhydride to the phenanthroline amine ligand was deemed successful by using proton and carbon NMR. The quantum yield of the new acetamide-phenanthroline ligand had reduced quantum yield as compared to the originally proposed ligand. This was investigated and concluded that the weaker electron-donating ability of the amide in this compound that is correlated to the carbonyl, negatively impacted the fluorescence of the europium complex. Future work will investigate coupling the monosubstituted PEG linker with the ligand by nucleophilic substitution of the bromine.

Additional Information

Language: English
Date: 2019
bioconjugate, lanthanide, pegylation, quantum yield

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