Bright Near-Infrared π-Conjugated Oligomer Nanoparticles for Deep-Brain Three-Photon Microscopy Excited at the 1700 nm Window in Vivo

Developing a 1700 nm excited three-photon fluorescent group is significant for achieving in vivo imaging of deep brain tissues. Professor Li Shengliang from Soochow University, Professor Wang Ke from Shenzhen University, and Chun-Sing Lee from City University of Hong Kong designed and synthesized a fluorescent molecule (OFET) and used it for three-photon microscopy imaging of live mouse brains at record imaging depths.

Key Points of This Article:

(1) OFET molecules have high fluorescence brightness. When integrated into water-dispersible nanoparticles (OEFT NPs), they exhibit near-infrared (NIR) maximum emission at 820 nm. Under 1720 nm excitation, the three-photon action cross-section of OFET NPs is 1.06×10⁻⁸² cm⁶ s²/photon², which is more than twice that of commonly used SR101 dye.

(2) Thanks to the long excitation wavelength 1720 nm in the second near-infrared region and the emission wavelength 820 nm in the first near-infrared region, which have high tissue penetration depth, high brightness, and large three-photon action cross-section, OFET NPs show good performance for deep brain imaging, clearly resolving mouse brain vasculature at a depth of 1696 μm, and showing no significant cytotoxicity even at high concentrations.

In summary, the fluorescent π-conjugated oligomers developed in this study have enormous application potential in high-resolution 3PM imaging of in vivo deep tissues.

References:

Shengliang Li. et al. Bright Near-Infrared π‑Conjugated Oligomer Nanoparticles for Deep-Brain Three-Photon Microscopy Excited at the 1700 nm Window in Vivo. ACS Nano. 2022

DOI: 10.1021/acsnano.2c03813

https://pubs.acs.org/doi/10.1021/acsnano.2c03813

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