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Facile Synthesis of Amine-Functionalized Eu 3+ -Doped La(OH) 3 Nanophosphors for Bioimaging

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ABSTRACT

Here, we report a straightforward synthesis process to produce colloidal Eu3+-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene glycol) serves as a high-boiling point solvent allowing for nanoscale particle formation as well as a convenient medium for solvent exchange and subsequent surface modification. The La(OH)3:Eu3+ NPs produced by this process were ~3.5 nm in diameter as determined by transmission electron microscopy. The NP surface was coated with aminopropyltriethoxysilane to provide chemical functionality for attachment of biological ligands, improve chemical stability and prevent surface quenching of luminescent centers. Photoluminescence spectroscopy of the NPs displayed emission peaks at 597 and 615 nm (λex = 280 nm). The red emission, due to 5D0 → 7F1 and 5D0 → 7F2 transitions, was linear with concentration as observed by imaging with a conventional bioimaging system. To demonstrate the feasibility of these NPs to serve as optical probes in biological applications, an in vitro experiment was performed with HeLa cells. NP emission was observed in the cells by fluorescence microscopy. In addition, the NPs displayed no cytotoxicity over the course of a 48-h MTT cell viability assay. These results suggest that La(OH)3:Eu3+ NPs possess the potential to serve as a luminescent bioimaging probe.

No MeSH data available.


Photoluminescence spectra of a as-synthesized NPs and b APTES-coated NPs (λex = 280 nm). Images of optical phantoms containing 5 mg/mL as-synthesized NPs a inset and APTES-coated NPs, b inset (λem = 575 - 650 nm).
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Figure 4: Photoluminescence spectra of a as-synthesized NPs and b APTES-coated NPs (λex = 280 nm). Images of optical phantoms containing 5 mg/mL as-synthesized NPs a inset and APTES-coated NPs, b inset (λem = 575 - 650 nm).

Mentions: The optical properties of the La(OH)3:Eu3+ NPs were evaluated by fluorescence spectroscopy under UV excitation in the broad Eu–O charge transfer band [35,36]. The photoluminescence spectra of the as-synthesized NPs, shown in Figure 4a (λex = 280 nm), display typical Eu3+ emission peaks at 597 and 615 nm due to the 5D0 → 7F1 (magnetic-dipole) and 5D0 → 7F2 (electronic-dipole) transitions, respectively. The emission spectra of APTES-coated NPs, shown in Figure 4b, display the same peak positions; however, the intensity of the 615-nm emission relative to the 5D0 → 7F1 is increased. The stronger 5D0 → 7F2 transition is likely due to the migration of Eu3+ ions to crystalline positions in the NP lattice during aging over the surface modification process. In addition, the intensity of emission in the red spectral region was enhanced by surface coating, as described previously. Analysis of the APTES-coated NP in an optical phantom (Figure 4b inset, 5 mg/mL) displayed ~44% enhancement in emission intensity when compared to bare NPs (Figure 4a inset).


Facile Synthesis of Amine-Functionalized Eu 3+ -Doped La(OH) 3 Nanophosphors for Bioimaging
Photoluminescence spectra of a as-synthesized NPs and b APTES-coated NPs (λex = 280 nm). Images of optical phantoms containing 5 mg/mL as-synthesized NPs a inset and APTES-coated NPs, b inset (λem = 575 - 650 nm).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211300&req=5

Figure 4: Photoluminescence spectra of a as-synthesized NPs and b APTES-coated NPs (λex = 280 nm). Images of optical phantoms containing 5 mg/mL as-synthesized NPs a inset and APTES-coated NPs, b inset (λem = 575 - 650 nm).
Mentions: The optical properties of the La(OH)3:Eu3+ NPs were evaluated by fluorescence spectroscopy under UV excitation in the broad Eu–O charge transfer band [35,36]. The photoluminescence spectra of the as-synthesized NPs, shown in Figure 4a (λex = 280 nm), display typical Eu3+ emission peaks at 597 and 615 nm due to the 5D0 → 7F1 (magnetic-dipole) and 5D0 → 7F2 (electronic-dipole) transitions, respectively. The emission spectra of APTES-coated NPs, shown in Figure 4b, display the same peak positions; however, the intensity of the 615-nm emission relative to the 5D0 → 7F1 is increased. The stronger 5D0 → 7F2 transition is likely due to the migration of Eu3+ ions to crystalline positions in the NP lattice during aging over the surface modification process. In addition, the intensity of emission in the red spectral region was enhanced by surface coating, as described previously. Analysis of the APTES-coated NP in an optical phantom (Figure 4b inset, 5 mg/mL) displayed ~44% enhancement in emission intensity when compared to bare NPs (Figure 4a inset).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Here, we report a straightforward synthesis process to produce colloidal Eu3+-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene glycol) serves as a high-boiling point solvent allowing for nanoscale particle formation as well as a convenient medium for solvent exchange and subsequent surface modification. The La(OH)3:Eu3+ NPs produced by this process were ~3.5 nm in diameter as determined by transmission electron microscopy. The NP surface was coated with aminopropyltriethoxysilane to provide chemical functionality for attachment of biological ligands, improve chemical stability and prevent surface quenching of luminescent centers. Photoluminescence spectroscopy of the NPs displayed emission peaks at 597 and 615 nm (λex = 280 nm). The red emission, due to 5D0 → 7F1 and 5D0 → 7F2 transitions, was linear with concentration as observed by imaging with a conventional bioimaging system. To demonstrate the feasibility of these NPs to serve as optical probes in biological applications, an in vitro experiment was performed with HeLa cells. NP emission was observed in the cells by fluorescence microscopy. In addition, the NPs displayed no cytotoxicity over the course of a 48-h MTT cell viability assay. These results suggest that La(OH)3:Eu3+ NPs possess the potential to serve as a luminescent bioimaging probe.

No MeSH data available.