Photon‐Upconverting Nanoparticles for Optical Encoding and Multiplexing of Cells, Biomolecules, and Microspheres

Abstract

Photon-upconverting nanoparticles (UCNPs) are lanthanide-doped nanocrystals that emit visible light under near-infrared excitation (anti-Stokes emission). This unique optical property precludes background fluorescence and light scattering from biological materials. The emission of multiple and narrow emission lines is an additional hallmark of UCNPs that opens up new avenues for optical encoding. Distinct emission signatures can be obtained if the multiple emission of UCNPs is tuned by their dopant composition or by surface modification with dyes. Tuning the intensity of only one of the multiple emission lines and using another one as a constant reference signal enables the design of ratiometric codes that are resistant to fluctuations in absolute signal intensities. Combining several UCNPs each displaying a distinct set of emission lines expands the coding capacity exponentially and lays the foundation for highly multiplexed analyte detection. This Review highlights the potential of UCNPs for labeling and encoding biomolecules, microspheres, and even whole cells.

Phase angle encoded upconversion luminescent nanocrystals for multiplexing applications

“…Inherited from the studies on fluorescent dyes and quantum dots, optical multiplexing strategies using UCNPs have been developed in the spectral domain 7,[24][25][26][27] , time domain 28 and spatial domain 29,30 . However, studies of the complex luminescence mechanisms involving sequential multi-step photophysical and energy transfer processes featuring complex luminescence kinetics are still at their infancy [31][32][33][34] , and may open possibility to develope unique multiplexing strategies in other domains.…”

Composite particles with magnetic properties, near-infrared excitation, and far-red emission for luminescence-based oxygen sensing

“…These advantageous features along with excellent photostability render UCLNPs highly attractive for bioimaging and bioanalytical applications [13][14][15][16] . Recently, UCLNPs have been employed as nanolamps for monitoring enzymatic reactions and for the determination of glucose and ethanol levels 17,18 .…”

A review of synthetic methods for the production of upconverting lanthanide nanoparticles

“…[4][5][6][7] For these reasons, UCNPs have been pursued as contrast agents for biomedical imaging during the past decade. [8][9][10][11] They are not, however, without disadvantages. Of primary concern is the low upconversion e±ciency of the base nanoparticles when compared to the downconversion luminescence of°uorescent dyes.…”