Development of highly luminescent and water-dispersible lanthanide-based nanomaterials for potential bio-medical imaging

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Gayanthi Kumari Attanayake (Creator)
Western Carolina University (WCU )
Web Site:
Channa De Silva

Abstract: Lanthanide metal ions exhibit fascinating optical and magnetic properties. Lanthanide-based nanomaterials have potential applications in optical devices, telecommunication, electroluminescent devices, bio-analytical sensors, and bio-medical imaging technology. Despite the recent developments, low luminescence characteristics, poor water solubility, and poor cell selectivity of lanthanide-based materials limit their use in bio-medical applications. This project is designed to mainly improve the luminescence properties of Eu(III)-based nanomaterials for their potential use in biomedical applications. In addition, we explore synthetic methods to enhance the water dispersibility and melanoma cell selectivity of the nanoparticles. Current research is designed to address the above mentioned drawbacks of lanthanide-based nanomaterials. Two different nanoparticle systems were developed in this project. i. europium (Eu)-based down-converting nanoparticles, ii. ytterbium (Yb)- erbium (Er)-based upconverting nanoparticles. Many down-converting nanoparticle systems suffer from low-luminescence efficiencies due to their poor light absorption by direct excitation of the lanthanide ions. In order to improve the luminescence characteristics, we have designed a novel nanomaterial by surface-coating it with organic chromophores having strong light absorption properties. LaEuF3.AEP (La=lanthanum, AEP = aminoethyl phosphate) nanoparticles were successfully synthesized using a low temperature heating method and Eu-based NaYF4 nanoparticles were synthesized using a high temperature heating method. A ligand exchange procedure was developed to functionalize the surface of the nanoparticles with an organic chromophore, TTA (thenoyltrifluoroacetone). The TTA functionalized Eu(III)-based nanoparticles exhibit impressive luminescence enhancements utilizing the sensitization effect. Poor water solubility is the main drawback of the upconverting nanoparticles for bio-medical applications. We have optimized a ligand exchange procedure to functionalize nanoparticle surface by using water soluble and highly coordinative aminoethyl phosphate (AEP) ligand. Water soluble AEP coated Yb- and Er-doped NaYF4 upconverting nanoparticles were prepared using high temperature method. The synthesized nanoparticles were characterized using UV-visible absorption, Fourier transform infrared (FT-IR), and fluorescence spectroscopic techniques, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and electron microscope techniques (TEM and SEM). Luminescent quantum yields of the down-converting nanoparticles were enhanced due to surface modification. The luminescence lifetime studies and luminescence enhancement of the nanoparticles will be discussed with an emphasis on their potential use in biomedical applications. Our attempts to improve the selectivity of the nanoparticles will be discussed where the nanoparticles were labeled with a melanocortin stimulating hormone (MSH4) peptide ligand targeted to human melanocortin receptors (hMCRs). Once fully developed, the nanoparticle platform has potential use in screening melanoma cancer cell surface-selective biomolecules and in vivo imaging of melanoma cancer.

Additional Information

Language: English
Date: 2013
Europium Nanoparticles, Luminescence, Quantum yields, Sensitization, Upconversion
Rare earth metals -- Optical properties -- Diagnostic use
Rare earth metals -- Solubility -- Diagnostic use
Nanostructured materials -- Optical properties -- Diagnostic use
Nanostructured materials -- Solubility -- Diagnostic use

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