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Upconversion nanomaterials: synthesis, mechanism, and applications in sensing.

Chen J, Zhao JX - Sensors (Basel) (2012)

Bottom Line: Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences.The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis.In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of North Dakota, Grand Forks, ND 58202, USA. jiao.chen@my.und.edu

ABSTRACT
Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

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In vivo cell viability of KB cells incubated with mPEG-UCNPs at different concentrations for 4–12 h [6].
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f8-sensors-12-02414: In vivo cell viability of KB cells incubated with mPEG-UCNPs at different concentrations for 4–12 h [6].

Mentions: Due to the rapid progress in developing UCNs’ applications in the biological field, the safety and toxicity of UCNs are a growing concern and extremely important. The most common methods to evaluate the toxicity are through cellular morphology and mitochondrial function, such as methylthiazolyl tetrazolium (MTT) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays. Studies have shown that UCNs are non-/low-toxicity to a broad range of cell lines [4,6,10,18,53,54]. The cells were usually treated with different concentrations of UCNs for various time range, and by measuring the cell viability percentage, the UCNs toxicity was determined. For example, in Zhang’s group, they studied both polyethyleneimine (PEI) [55] and silica-coated [18] UCNs’ cell toxicity. In the case of silica-coated UCNs, although the cell viability decreased as a function of both concentration and time, 93.4% of skeletal myoblast cells and 93.2% of BMSCs cells were still alive under 24 h incubation at a concentration of 1 μg/mL, which indicated great biocompatibility [18]. Recently, Li and co-workers investigated the UCNs’ long-term in vivo distribution and toxicity [56]. Their findings show that the mice survived for 115 days after the intravenously injection 15 mg/kg of UCNs with no apparent adverse effects observed to their health, indicating the possibility for long-term targeted imaging and therapy studies in vivo. Hu et al. treated the KB cells with different concentrations of PEG-modificed UCNs (Figure 8) [6]. Even at a high concentration of 250 μg/mL, the cell viability still remained above 80%, showing the low cytotoxicity of the nanoparticles.


Upconversion nanomaterials: synthesis, mechanism, and applications in sensing.

Chen J, Zhao JX - Sensors (Basel) (2012)

In vivo cell viability of KB cells incubated with mPEG-UCNPs at different concentrations for 4–12 h [6].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376553&req=5

f8-sensors-12-02414: In vivo cell viability of KB cells incubated with mPEG-UCNPs at different concentrations for 4–12 h [6].
Mentions: Due to the rapid progress in developing UCNs’ applications in the biological field, the safety and toxicity of UCNs are a growing concern and extremely important. The most common methods to evaluate the toxicity are through cellular morphology and mitochondrial function, such as methylthiazolyl tetrazolium (MTT) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays. Studies have shown that UCNs are non-/low-toxicity to a broad range of cell lines [4,6,10,18,53,54]. The cells were usually treated with different concentrations of UCNs for various time range, and by measuring the cell viability percentage, the UCNs toxicity was determined. For example, in Zhang’s group, they studied both polyethyleneimine (PEI) [55] and silica-coated [18] UCNs’ cell toxicity. In the case of silica-coated UCNs, although the cell viability decreased as a function of both concentration and time, 93.4% of skeletal myoblast cells and 93.2% of BMSCs cells were still alive under 24 h incubation at a concentration of 1 μg/mL, which indicated great biocompatibility [18]. Recently, Li and co-workers investigated the UCNs’ long-term in vivo distribution and toxicity [56]. Their findings show that the mice survived for 115 days after the intravenously injection 15 mg/kg of UCNs with no apparent adverse effects observed to their health, indicating the possibility for long-term targeted imaging and therapy studies in vivo. Hu et al. treated the KB cells with different concentrations of PEG-modificed UCNs (Figure 8) [6]. Even at a high concentration of 250 μg/mL, the cell viability still remained above 80%, showing the low cytotoxicity of the nanoparticles.

Bottom Line: Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences.The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis.In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of North Dakota, Grand Forks, ND 58202, USA. jiao.chen@my.und.edu

ABSTRACT
Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

Show MeSH