Chemistry Reference
In-Depth Information
nanoparticles are not very popular because of their inherent
limitations of low penetration depth and high phototoxicity, and
hence downconversion nanoparticles are finding applications
mainly in electronics and optics rather than biology. Significant
studies have been done in the last decade for developing these rare
earth nanomaterials with upconversion fluorescence as an excellent
fluorescent label for different fluorescence microscopy applications.
Such upconversion nanomaterials, absorbing in the NIR and
emitting in the visible/NIR regions, have significantly contributed to
improvement in resolution, sensitivity and decrease in background
autofluorescence in fluorescence microscopy techniques. The use of
NIR as an excitation source has advantages such as low phototoxicity
and high signal-to-noise ratio as NIR does not excite biological
samples and, hence, has negligible background autofluorescence.
Despite rapid development in this field, there are still many challenges
and avenues for improvement. The only advantage of organic dyes
over these nanoparticles is their smaller size. So the development of
sub-10 nm nanoparticles with good upconversion fluorescence will
allow the fluorescence labeling of intracellular components.
Various reports show the promise of lanthanide-doped
upconversion nanoparticles in deep tissue
fluorescence
microscopy. However, there is a long way to go before it reaches
clinical testing. More studies are needed to improve the imaging
depth and resolution
in vivo
. This is possible with the current
development of lanthanide-doped upconversion nanoparticles with
the capabilities of multimodal imaging. Syntheses of nanoparticles,
which show upconversion fluorescence and MRI contrast, have been
reported. But incorporation of isotopes such as
in vivo
I can be
done to enable other multimodal imaging techniques such as PET
and SPECT in combination with fluorescence imaging using the
upconversion fluorescence. All these developments will give a new
dimension to
124
I or
125
fluorescence molecular imaging.
Thus the use of fluorescent rare earth nanomaterials in fluorescence
imaging techniques is a burgeoning, interdisciplinary field holding a
lot of promise in the years to come.
in vitro
and
in vivo
Acknowledgements
The authors would like to acknowledge the financial support from
Singapore A*STAR SBIC and National University of Singapore.
