Attention:

Certain features of Sigma-Aldrich.com will be down for maintenance the evening of Friday August 18th starting at 8:00 pm CDT until Saturday August 19th at 12:01 pm CDT.   Please note that you still have telephone and email access to our local offices. We apologize for any inconvenience.

Sunstone® Luminescent UCP Nanocrystals

For more information, please contact monika.baeumle@sial.com

For Low Background Detection in Life Science Applications

  • Eliminate autofluorescence in biological samples
  • Large anti-Stokes shift produces discrete emission signals for multiplex techniques
  • Resistant to photobleaching and fading
  • Biocompatible and non-toxic
  • Small particle size for life science applications

Upconversion Imaging Background

While fluorescent imaging applications are commonly used in life science research, inherent limitations to fluorescence, especially for cellular applications, have encouraged development of alternative techniques and compounds. Upconversion luminescence using rare-earth doped nanocrystals is increasingly being used in commercial and industrial applications and more recently has been used in life science applications to overcome these limitations found with quantum dots and other normal fluorophores (see Figure 1).

Illustration of fundamental difference between quantum dots with normal fluorescence and upconversion nanocrystals

Figure 1. Illustration of fundamental difference between quantum dots with normal fluorescence and upconversion nanocrystals.

Normal fluorescence converts higher-energy (shorter wavelength) light to lower-energy (longer wavelength) emitted light. Upconversion luminescence is based on the absorption of two or more low-energy (longer wavelength, typically infrared) photons by a nanocrystal followed by the emission of a single higher-energy (shorter wavelength) photon (see Figure 2). This energy transfer is most often accomplished using a combination of rare-earth lanthanides as dopants on ceramic microparticles. Upconversion luminescence is a unique process and does not occur in nature.

Simplified principle of up-conversion luminescence

Figure 2: Simplified principle of up-conversion luminescence. Two or more low-energy photons (longer infrared wavelength) are absorbed by an upconverting phosphor followed by the emission of a single higher-energy photon (shorter visible wavelength).

The ability to adjust the size, morphology, absorption, emission, rise time, decay time, power density, and other properties of upconversion nanocrystals enables the formation of materials with an infinite amount of distinctive signatures. Upconversion crystals and nanocrystals with sizes ranging from 5 nm to 400 microns have been prepared, and the morphology of the crystals can be spherical, hexagonal, cubic, rod-shaped, diamond-shaped, and random.

Upconversion nanocrystals do not photobleach and allow permanent excitation with simultaneous signal integration. They can be stored indefinitely without a decrease in light emitting efficiency and thus allow repeated irradiation and analysis.

Sunstone® Upconverting Nanocrystals (Sunstone UCP Nanocrystals)

Sunstone Nanocrystals from Intelligent Material Solutions® Inc. are a proprietary, novel series of rare earth-doped nanocrystals of small size, high quantum efficiency, and high photoluminescent intensity functionalized for use in industrial and life sciences applications. These patented materials possess unique and inherent atomic states that allow the conversion of various wavelengths of light energy up and down the electromagnetic spectrum.

Sunstone Nanocrystals are synthesized using specific compositions of individual rare earths and other host elements. Upconversion luminescence by Sunstone Nanocrystals occurs through a combination of a trivalent rare-earth sensitizer (e.g. Yb, Nd, Er, or Sm) as the element that initially absorbs the electromagnetic radiation and a second lanthanide activator (e.g. Er, Ho, Pr, Tm) ion in an optical passive crystal lattice that serves as the emitting elements. By varying the concentrations and ratios of rare earths, different emission spectra can be elicited from the same combination of elements.

Eliminate Autofluorescence in Biological Samples
Upconversion bioimaging has significantly lower autofluorescence (see Figure 3) and a higher signal to noise ratio when compared to single-photon excitation for fluorescence detection.

Comparison of Sunstone Upconversion Nanocrystals to fluorescein

Figure 3. Comparison of Sunstone Upconversion Nanocrystals (left) to fluorescein (right) for imaging of prostate serum antigen (PSA) in human prostate cancer immunohistology sample. Notice the absence of tissue autofluorescence in the sample detected using Sunstone Upconversion nanocrystals (left).
Figure provided by Intelligent Materials, Inc.
(Dr. Sam Niedbala, Lehigh University)

Large Anti-Stokes Shift for Discrete Emission Signals in Multiplex Techniques
A large anti-Stokes shift (up to 500 nm) with upconversion phosphorescence means well-separated and discrete emission peaks from the infrared excitation source. For NIR emitting nanoparticles, the longer wavelength allows deeper penetration of the exciting light into biological tissues. Furthermore, by varying the concentration and ratio of lanthanides, the decay time of Sunstone nanocrystals can be modified from less than a femtosecond to a millisecond or longer, and these temporal properties are reproducible for a specific formulation, ensuring consistency in replicate tests. Standard detectors can easily differentiate these temporal signatures. A combination of Sunstone Nanocrystals can be applied in an assay using a single excitation source to produce different emission signals for multiplex applications.

Small Particle Size for Life Science Applications
Sunstone Nanocrystals available through Sigma-Aldrich are 30 nm rods, which are small enough for life science applications without further processing (see Figure 4). Sunstone Nanocrystals have a high degree of structural homogeneity, allowing for finely tuned temporal properties and narrow spectral emission. The nanocrystals are synthesized in the β crystal phase (β-NaYF4), requiring low phonon energy for upconversion.1 Sunstone Nanocrystals exhibit excellent size distribution, uniformity in shape, and high monodispersity.

Additional sizes and morphologies of Sunstone Nanocrystals will be made available in the future to support life science research.

Transmission electron microscope images of rod-shaped ~30-nm NaYF4 Sunstone Upconverting Nanocrystals

Figure 4. Transmission electron microscope images of rod-shaped ~30-nm NaYF4 Sunstone Upconverting Nanocrystals. Sunstone Nanocrystals exhibit excellent size distribution, uniformity in shape, and high monodispersity.

Resistant to Photobleaching and Fading
Sunstone Upconverting Nanocrystals do not photobleach and allow permanent excitation with simultaneous signal integration. They can be stored indefinitely without a decrease in light emitting efficiency for repeated irradiation and analysis.

Biocompatible and Non-Toxic
Sunstone Nanocrystals are biocompatible and non-toxic20, with no cytotoxicity against human osteosarcoma cells.2  Upconverting nanocrystals have been used in in vivo experiments with C. elegans3 and mice4 without demonstrating toxicity.

Life Science Applications

Upconverting materials have been used in a broad variety of life science applications including:

  • Immunohistochemistry2,5-7
  • Immunocytochemistry5-7
  • Multiplex immunoassays5,6
  • Nucleic acid microarrays6,8,9
  • In vivo, in situ, and ex situ biomedical imaging2,3,5,10,11, 17, 18, 19
  • Flow cytometry8,12
  • Enzymatic assays6,8,12
  • Fluorescence resonance energy transfer (FRET) bioanalytical assays12

Sunstone Nanocrystals are ideal for life science detection and imaging with broad applicability in many in vitro and in vivo techniques. Sunstone Nanocrystals are extremely robust and can be incorporated into many chemical and biochemical compositions without losing their phosphorescence as long as the medium in which they are dispersed is optically transparent to both the absorbed and emitted radiation. Unlike larger upconverting particles  (200-400 nm), Sunstone Nanocrystals have a 30 nm core, allowing them to be used in life science applications including in vivo imaging without prior milling.

With sharp emission bands and large anti-Stokes shifts, Sunstone Nanocrystals may be used in multiplex techniques allowing identification of multiple emission spectra from a single sample (see Figure 5). The nanocrystals are also suitable for FRET based assay systems.

Simultaneous dual-label imaging of CD-4 and CD-3 human lymphocytes

Figure 5. Simultaneous dual-label imaging of CD-4 and CD-3 human lymphocytes using antibodies conjugated to different Sunstone Nanocrystals.
    CD-3: Yb:Er doped, green emission
    CD-4, Yb:Tm doped, blue emission
Figure provided by Intelligent Materials, Inc.
(Dr. Sam Niedbala, Lehigh University)

Sunstone Nanocrystals have been used for in vivo and in situ macroscopic lymphatic imaging in mice (see Figure 6). Multiplex analysis using 980 nm excitation was performed by using a combination of green-emitting and red-emitting upconversion particles.4

Luminescent in vivo and in situ lymphatic imaging with infrared Sunstone Upconverting nanocrystals

Figure 6. Luminescent in vivo and in situ lymphatic imaging with infrared Sunstone Upconverting nanocrystals obtained with both spectral and single shot imaging. The nanocrystals depicted the draining lymph nodes during in vivo and in situ imaging in mice. Due to the minimal background, single shot luminescence images obtained at 800 nm were comparable to the spectrally unmixed images which were post processed to remove autofluorescence4. (Dr. Hisataka Kobayashi, National Institutes of Health)

Carboxylated Sunstone Nanocrystals may be attached to biomolecules via the carboxyl group after EDC activation. Carboxylated nanocrystals can also be conjugated via electrostatic binding. Carboxylated Sunstone Nanocrystals can be conjugated to a variety of biomolecules including:

  • Antibodies
  • Enzymes
  • Substrates
  • Small molecules and inhibitors

Avidin conjugated Sunstone Nanocrystals can be used in common biotin-avidin/streptavidin reporter systems.

Ordering Information

Product No. Description Functional Group λEx (nm) λEm max. (nm)* Crystal morphology Add to Cart
89157 Sunstone Upconverting nanocrystals UCP 804, carboxylated Carboxyl 976 804 10 - 60
nm rods
61334 Sunstone Upconverting nanocrystals UCP 545, carboxylated Carboxyl 976 545 10 - 60
nm rods
66698 Sunstone Upconverting nanocrystals UCP 538, carboxylated Carboxyl 976 538 10 - 60
nm rods
90838 Sunstone Upconverting nanocrystals UCP 475, carboxylated Carboxyl 976 475 10 - 60
nm rods
76736 Sunstone Upconverting nanocrystals UCP 804, streptavidin conjugated Streptavidin 976 804 10 - 60
nm rods
90992 Sunstone Upconverting nanocrystals UCP 545, streptavidin conjugated Streptavidin 976 545 10 - 60
nm rods
75207 Sunstone Upconverting nanocrystals UCP 538, streptavidin conjugated Streptavidin 976 538 10 - 60
nm rods
89043 Sunstone Upconverting nanocrystrals UCP 475, streptavidin conjugated Streptavidin 976 475 10 - 60
nm rods
67345 Sunstone Upconverting nanocrystals UCP 475 no 976 475 10 - 60
nm rods
57688 Sunstone Upconverting nanocrystals UCP 475, amin conjugated amine 976 475 10 - 60
nm rods
74932 Sunstone Upconverting nanocrystals UCP 538 no 976   10 - 60
nm rods
52498 Sunstone Upconverting nanocrystals UCP 538, amine conjugated amine 976 538 10 - 60
nm rods
73909 Sunstone Upconverting nanocrystals UCP 538, biotin conjugated biotin 976 538 10 - 60
nm rods
74344 Sunstone Upconverting nanocrystals UCP 545, amine conjugated amine 976 545 10 - 60
nm rods
79882 Sunstone Upconverting nanocrystals UCP 545, biotin conjugated biotin 976 545 10 - 60
nm rods
53367 Sunstone Upconverting nanocrystals UCP 804 no 976 804 10 - 60
nm rods
73702 Sunstone Upconverting nanocrystals UCP 804, amine conjugated amine 976 804 10 - 60
nm rods
43177 Sunstone Upconverting nanocrystals UCP 804, biotin conjugated biotin 976 804 10 - 60
nm rods
08389 Sunstone Upconverting nanocrystals UCP 538
none 976 538 ≤ 150 nm, diamonds
06741 Sunstone Upconverting nanocrystals UCP 545 none 976 545 ≤ 150 nm, diamonds
40473 Sunstone Upconverting nanocrystals UCP 804 none 976 804 ≤ 150 nm, diamonds
88791 Sunstone Upconverting nanocrystals UCP 538, amine conjugated Amine 976 538 ≤ 150 nm, diamonds
44439 Sunstone Upconverting nanocrystals UCP 545, amine conjugated Amine 976 545 ≤ 150 nm, diamonds
91562 Sunstone Upconverting nanocrystals UCP 804, amine conjugated Amine 976 804 ≤ 150 nm, diamonds
94203 Sunstone Upconverting nanocrystals UCP 538, carboxylated Carboxyl 976 538 ≤ 150 nm, diamonds
01500 Sunstone Upconverting nanocrystals UCP 545, carboxylated Carboxyl 976 545 ≤ 150 nm, diamonds
75122 Sunstone Upconverting nanocrystals UCP 804, carboxylated Carboxyl 976 804 ≤ 150 nm, diamonds
43587 Sunstone Upconverting nanocrystals UCP 538, streptavidin conjugated Streptavidin 976 538 ≤ 150 nm, diamonds
76889 Sunstone Upconverting nanocrystals UCP 545, streptavidin conjugated Streptavidin 976 545 ≤ 150 nm, diamonds
39456 Sunstone Upconverting nanocrystals UCP 804, streptavidin conjugated Streptavidin 976 804 ≤ 150 nm, diamonds
43722 Sunstone Upconverting nanocrystals UCP 538, biotin conjugated Biotin 976 538 ≤ 150 nm, diamonds
78269 Sunstone Upconverting nanocrystals UCP 545, biotin conjugated Biotin 976 545 ≤ 150 nm, diamonds
72577 Sunstone Upconverting nanocrystals UCP 804, biotin conjugated Biotin 976 804 ≤ 150 nm, diamonds

*Refers to strongest signal.

Sunstone is a registered trademark of Intelligent Material® Solutions Inc.
Sunstone upconverting nanocrystals are produced under license from SRI International.

 

FAQ

  1. What is upconversion fluorescence / phosphorescence / luminescence?
    Normal fluorescence converts higher-energy (shorter wavelength) light to lower-energy (longer wavelength) emitted light. Upconversion luminescence is based on the absorption of two or more low energy (longer wavelength) photons followed by emission of a single higher energy (shorter wavelength) photon. Most upconversion luminescent materials operate by using the combination of a trivalent rare-earth sensitizer (e.g. Yb, Er or Sm) and a second lanthanide activator (e.g. Er, Ho, Pr, Tm) ion in an optically passive crystal lattice.

  2. What is the average crystal size of the Sunstone® Upconverting Nanocrystals?
    The Sunstone Upconverting Nanocrystals particle core has an average diameter of 30 nm. The hydrodynamic diameter is higher, depending of the environment. Additional sizes and morphologies of Sunstone Nanocrystals will be made available in the future to support life science research. For specific inquiries, please contact Sigma Technical Services.

  3. What life science applications are Sunstone® Upconverting Nanocrystals used for?
    Sunstone Upconverting Nanocrystals have a variety of life science applications including immunohistochemistry, immunocytochemistry, multiplex immunoassay techniques, nucleic acid microarrays, biomedical imaging, flow cytometry, enzymatic assays, and fluorescence resonance energy transfer (FRET) bioanalytical assays.  Other industrial applications for upconversion particles include use in lasers, displays, quantum counters, and inks for security printing.

  4. What kind of luminescence do Sunstone® Upconverting Nanocrystals have?
    Sunstone Upconverting Nanocrystals emit visible or near infrared phosphorescence light after excitation, typically with infrared (980 nm) light.

  5. What is the chemical nature of the surface of Sunstone® Upconverting Nanocrystals?
    Sunstone Upconverting Nanocrystals are available with surface modification for subsequent covalent binding of target molecules e.g., biomolecules (antibodies or streptavidin), linkers, or inorganic substances. The nanocrystal surface is based on PEG-derivatives that may have additional carboxyl (-COOH), biotin, or amine functional groups.

 

Instrumentation Recommendations

The following are representative of instruments suitable for near-IR upconversion phosphorescence using Sunstone® Nanocrystals, but is not meant to be an all-inclusive list of instruments.

Spectrometers

  • Cary Eclipse fluorescence spectrophotometer (Agilent Technologies, USA) with a standard R928 red-sensitive photomultiplier (Hamamatsu Photonics, Japan) was equipped with IR laser diode module C2021-F1 (Roithner Lasertechnik, Austria). An IR laser diode module and a long-pass filter glass RG-850 (Andover Corporation, USA) was mounted to a cuvette holder of the spectrophotometer. Emitted light was collected using bio/chemiluminescence mode of the spectrophotometer from 350 to 850 nm.12
  • Fiber-optically coupled USB4000 fluorescence spectrometer (Ocean Optics, USA) using an external continuous-wave laser centered at ~980 nm as the excitation source (Dragon  Lasers, China).1

Benchtop Scanner

  • 96-well FluoroCount microtiter plate reader (Perkin Elmer, USA) modified with an external 980 nm 1.2W IR laser (Oclaro, USA).9

Microscopes

  • Inverted fluorescence microscope (Leica Microsystems, Germany) equipped with a 980 nm NIR laser and a Nikon digital camera.12
  • Epifluorescence microscope (Leica Microsystems, Germany) modified with a 980 nm light from a xenon XBO 75 W lamp.9
  • Olympus microscopes using 975 diode laser (QPhotonics LLC, USA); with a laser diode driver; Thorlabs LDC 30 65 – 488. Detection: xy translation monitored filter coupled; Ocean Optics, USB 2000.

In vivo Imaging

  • Maestro in vivo spectral imaging system (CRI Inc., USA) equipped with a 980 nm diode laser excitation source (B&W TEK Inc., USA).4

Other Possible Excitation Laser Sources

  • JDSU 3000 series 660 mW Fiber Bragg grating stabilized 976 +/- 1 nm pump module (PN 30-7602-660).
  • Edmund Optics fiber laser 976 nm 450 mW (PN NT62-688).
  • Newport LD Module, 980 nm, 220 mW, CW – (Model: LQC980-220E)

References

  1. Feng Wang, Debapriya Banerjee,Yongsheng Liu, Xueyuan Chenc and Xiaogang Liu, Analyst, 2010, 135, 1839–1854

    1b. Ye, X., Collins, J.E., Kang, Y., Chen, J., Chen, D.T., Yodh, A.G., and Murray, C.B. Morphologically controlled synthesis of colloidal upconversion nanophosphors and their shape-directed self-assembly. Proc. Natl. Acad. Sci. USA, 107, 22430-5 (2010).

  2. Shan, J., Chen, J., Meng, J., Collins, J., Soboyejo, W., Friedberg, J.S., and Ju, Y. Biofunctionalization, cytotoxicity, and cell uptake of lanthanide doped hydrophobically ligated NaYF4 upconversion nanophosphors. J. Appl. Phys., 104, 094308 (2008).

  3. Lim, S.F., Riehn, R., Ryu, W.S., Khanarian, N., Tung, C.K., Tank, D., and Austin, R.H. In vivo and scanning electron microscopy imaging of upconverting nanophosphors in Caenorhabditis elegans. Nano Lett., 6, 169-74 (2006).

  4. Kobayashi, H., Kosaka, N., Ogawa, M., Morgan, N., Smith, P.D., Murray, C.B., Ye, X., Collins, J., Kumar, G.A., Bell, H., and Choyke, P.L. In vivo multiple color lymphatic imaging using upconverting nanocrystals. J. Mater. Chem., 19, 6481–84 (2009).

  5. Bünzli, J-C.G. Lanthanide luminescence for biomedical analyses and imaging. Chem. Rev., 110, 2729–55 (2010).

  6. Corstjens, P., Chen, Z., Zuiderwijk, M., Bau, H.H., Abrams, W.R., Malamud, D., Sam Niedbala, R., and Tanke, H.J. Rapid assay format for multiplex detection of humoral immune responses to infectious disease pathogens (HIV, HCV, and TB). Ann. N.Y. Acad. Sci., 1098, 437-445 (2007).

  7. Wang, M., Mi, C.-C., Wang, W.-X., Liu, C.-H., Wu, Y.-F., Xu, Z.-R., Mao, C.-B., and Xu, S.-K. Immunolabeling and NIR-excited fluorescent imaging of HeLa cells by using NaYF4:Yb,Er upconversion nanoparticles. J. Phys. Chem., 113, 19021-7 (2009).

  8. Abrams, W.R., Barber, C.G., McCann, K., Tong, G., Chen, Z., Mauk, M.G., Wang, J., Volkov, A., Bourdelle, P., Corstjens, P.L., Zuiderwijk, M., Kardos, K., Li, S., Tanke, H.J., Sam Niedbala, R., Malamud, D., and Bau, H. Development of a microfluidic device for detection of pathogens in oral samples using upconverting phosphor technology (UPT). Ann. N.Y. Acad. Sci., 1098, 375-388 (2007).

  9. Corstjens, P.L.A.M., Li, S., Zuiderwijk, M., Kardos, K., Abrams, W.R., Niedbala, R.S. and Tanke, H.J. Infrared up-converting phosphors for bioassays. IEE Proc. Nanobiotechnol., 152, 64–72 (2005).

  10. Xue, X., Wang, F., and Liu, X. Emerging functional nanomaterials for therapeutics. J. Mater. Chem., 21, 13107-13127 (2011).

  11. Chatterjee, D.K., and Yong, Z. Upconverting nanoparticles as nanotransducers for photodynamic therapy in cancer cells. Nanomedicine (Lond.), 3, 73 -82 (2008).

  12. Soukka, T., Kuningas, K., Rantanen, T., Haaslahti, V., and Lövgren, T. Photochemical characterization of up-converting inorganic lanthanide phosphors as potential labels. J. Fluoresc., 15, 513-28 (2005).

  13. Wang, M., Mi, C.-C., Wang, W.-X., Liu, C.-H., Wu, Y.-F., Xu, Z.-R., Mao, C.-B., and Xu, S.-K. Immunolabeling and NIR-excited fluorescent imaging of HeLa cells by using NaYF(4):Yb,Er upconversion nanoparticles. ACS Nano, 3, 1580-6 (2009).

  14. Kokko, T., Liljenback, T., Peltola, M.T., Kokko, L., and Soukka, T. Homogeneous dual-parameter assay for prostate-specific antigen based on fluorescence resonance energy transfer. Anal. Chem., 80, 9763–8 (2008).

  15. Soukka, T., Rantanen, T., and Kuningas, K. Photon upconversion in homogeneous fluorescence-based bioanalytical assays. Ann. N.Y. Acad. Sci., 1130, 188–200 (2008).

  16. Zijlmans, H.J.M.A.A., Bonnet, J., Burton, J., Kardos, K., Vail, T., Niedbala, R.S., and Tanke H.J. Detection of cell and tissue surface antigens using up-converting phosphors: A new reporter technology. Anal. Biochem., 267, 30–36 (1999).

  17. M González-Béjar et al., Upconversion Nanoparticles for Bioimaging and Regenerative Medicine, Front Bioeng Biotechnol. 2016, 4, 47

  18. Feng Chen, Wembo Bu, Weibo Cai, Jialin Shi, Functionalized Upconversion Nanoparticles: Versatile Nanoplatform for Translational Research, Curr Mol Med, 2013 Dec; 13 (10); 1613 – 1632

  19. Scott A. Hildebrand, Fangwei Shao, Christopher Salthouse, Umar Mahmood, Ralph Weissleder, Upconversion Luminescent Nanomaterial: Application to In Vivo Bioimaging, Chem Commun (Camb) 2009, Jul 28 (28); 4188-4190

  20. Maria V. Vedunova, Tatiana A. Mishchenko, Elena V. Mitroshina, Natalia V. Ponomareva, Andrei V. Yudintev, All N. Generalo, Sergey M. Devev, Irina V. Mukhina, Alexey V. Semyanov, Andrei V. Zvyagin, Cytotoxic effects of upconversion nanoparticles in primary hippocampal cultures, RSC Advanced, 2016, Issue 40, in progress

 

For further questions, please contact Product Manager monika.baeumle@sial.com.