Low irradiance multiphoton imaging with alloyed lanthanide nanocrystals.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30082844.
- Also identified by DOI 10.1038/s41467-018-05577-8 and PMC identifier 6079005.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Multiphoton imaging techniques that convert low-energy excitation to higher energy emission are widely used to improve signal over background, reduce scatter, and limit photodamage. Lanthanide-doped upconverting nanoparticles (UCNPs) are among the most efficient multiphoton probes, but even UCNPs with optimized lanthanide dopant levels require laser intensities that may be problematic. Here, we develop protein-sized, alloyed UCNPs (aUCNPs) that can be imaged individually at laser intensities >300-fold lower than needed for comparably sized doped UCNPs. Using single UCNP characterization and kinetic modeling, we find that addition of inert shells changes optimal lanthanide content from Yb<sup>3+</sup>, Er<sup>3+</sup>-doped NaYF<sub>4</sub> nanocrystals to fully alloyed compositions. At high levels, emitter Er<sup>3+</sup> ions can adopt a second role to enhance aUCNP absorption cross-section by desaturating sensitizer Yb<sup>3+</sup> or by absorbing photons directly. Core/shell aUCNPs 12 nm in total diameter can be imaged through deep tissue in live mice using a laser intensity of 0.1 W cm<sup>-2</sup>.