Reversibly Photoswitching Upconversion Nanoparticles for Super-Sensitive Photoacoustic Molecular Imaging.

Angew Chem Int Ed Engl

Molecular Imaging Program at Stanford, Departments of Radiology and Chemistry, School of Medicine, Stanford University, Stanford, CA 94305, USA.

Published: May 2022

Photoacoustic (PA) imaging uses light excitation to generate the acoustic signal for detection and improves tissue penetration depth and spatial resolution in the clinically relevant depth of living subjects. However, strong background signals from blood and pigments have significantly compromised the sensitivity of PA imaging with exogenous contrast agents. Here we report a nanoparticle-based probe design that uses light to reversibly modulate the PA emission to enable photoacoustic photoswitching imaging (PAPSI) in living mice. Such a nanoprobe is built with upconverting nanocrystals and photoswitchable small molecules and can be switched on by NIR light through upconversion to UV energy. Reversibly photoswitching of the nanoprobe reliably removed strong tissue background, increased the contrast-to-noise ratio, and thus improved imaging sensitivity. We have shown that PAPSI can image 0.05 nM of the nanoprobe in hemoglobin solutions and 10 labeled cancer cells after implantation in living mice using a commercial PA imager.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9038665PMC
http://dx.doi.org/10.1002/anie.202116802DOI Listing

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