Photoacoustic and photothermal cytometry using photoswitchable proteins and nanoparticles with ultrasharp resonances

Ekaterina I. Galanzha, Dmitry A. Nedosekin, Mustafa Sarimollaoglu, Anamaria Ioana Orza, Alexandru S. Biris, Vladislav V. Verkhusha, Vladimir P. Zharov

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Photoswitchable fluorescent proteins (PSFPs) with controllable spectral shifts in emission in response to light have led to breakthroughs in cell biology. Conventional photoswitching, however, is not applicable to weakly fluorescent proteins. As an alternative, photothermal (PT) and photoacoustic (PA) spectroscopy have demonstrated a tremendous potential for studying absorbing nonfluorescent proteins and nanoparticles. However, little progress has been made in the development of switchable PT and PA probes with controllable spectral shifts in absorption. Here, we introduce the concept of photothermally switchable nanoparticles (PTSNs). To prove the concept, we demonstrated fast, reversible magnetic-PT switching of conventional and gold-coated magnetic nanoparticle clusters in cancer cells in vitro and PT switching of nonlinear ultrasharp plasmonic resonances in gold nanorods molecularly targeted to circulating cells in vivo. We showed that genetically encoded PSFPs with relatively slow switching can serve as triple-modal fluorescent, PT, and PA probes under static conditions, while PTSNs with ultrafast switching may provide higher PA sensitivity in the near-infrared window of tissue transparency under dynamic flow conditions. Application of nonlinear phenomena for super-resolution spectral PT and PA cytometry, microscopy, and spectral burning beyond the diffraction and spectral limits are also proposed. (

Original languageEnglish (US)
Pages (from-to)81-93
Number of pages13
JournalJournal of Biophotonics
Issue number1-2
StatePublished - Jan 1 2015


  • Circulating cells
  • Photoswitchable fluorescent proteins
  • Photothermal and photoacoustic spectroscopy
  • Photothermal switching
  • Plasmonic nanoparticles
  • Ultrasharp spectral resonances
  • in vivo flow cytometry

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Engineering(all)
  • Physics and Astronomy(all)


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