Reversibly Photoswitching Upconversion Nanoparticles for Super-Sensitive Photoacoustic Molecular Imaging

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

14 Scopus Citations
View graph of relations


  • Cheng Liu
  • Xianchuang Zheng
  • Tingting Dai
  • Huiliang Wang
  • Bing Chen
  • Steven Chu
  • Jianghong Rao


Original languageEnglish
Article numbere202116802
Journal / PublicationAngewandte Chemie (International Edition)
Publication statusOnline published - 9 Feb 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 104 labeled cancer cells after implantation in living mice using a commercial PA imager.

Research Area(s)

  • Imaging Agents, Near-infrared, Photoacoustic Imaging, Reversible Photoswitching, Upconversion Nanoparticles, SEMICONDUCTING POLYMER NANOPARTICLES, TOMOGRAPHY, MICROSCOPY, RECEPTOR, AGENT