In Vivo High-resolution Ratiometric Fluorescence Imaging of Inflammation Using NIR-II Nanoprobes with 1550 nm Emission

Abstract

Quantitatively imaging the spatiotemporal distribution of biological events in living organisms is essential to understand fundamental biological processes. Self-calibrating ratiometric fluorescent probes enable accurate and reliable imaging and sensing, but conventional probes using wavelength of 400–900 nm suffer from extremely low resolution for in vivo application due to the disastrous photon scattering and tissue autofluorescence background. Here, we develop a NIR-IIb (1500–1700 nm) emissive nanoprobe for high-resolution ratiometric fluorescence imaging in vivo. The obtained nanoprobe shows fast ratiometric response to hypochlorous acid (HOCl) with a detection limit down to 500 nM, through an absorption competition-induced emission (ACIE) bioimaging system between lanthanide-based downconversion nanoparticles and Cy7.5 fluorophores. Additionally, we demonstrate the superior spatial resolution of 1550 nm to a penetration depth of 3.5 mm in a scattering tissue phantom, which is 7.1-fold and 2.1-fold higher than that of 1064 and 1344 nm, respectively. With this nanoprobe, clear anatomical structures of lymphatic inflammation in ratiometric channel are observed with a precise resolution of ∼477 μm. This study will motivate the further research on the development of NIR-II probes for high-resolution biosensing in vivo.

Novel NIR-II organic fluorophores for bioimaging beyond 1550 nm

“…13 Very few inorganic NIR-IIb uorophores such as single-walled carbon nanotubes (SWNTs), rare earth doped nanoparticles, and quantum dots have been investigated for biosensing and bioimaging beyond 1500 nm. 7g,8f, [13][14][15][16][17] It is worth noting that organic FD-1080 J-aggregates were rst accomplished with high resolution imaging of the cerebral and hindlimb vasculature with uorescence emission tailing into 1500 nm with a quantum yield (QY) of 0.0545%. 17 The signal-tobackground ratio (SBR) was 3.3-fold higher than that of NIR-IIa (1300-1400 nm) imaging.…”

Tm3+‐Sensitized NIR‐II Fluorescent Nanocrystals for In Vivo Information Storage and Decoding

“…Within the NIR‐II window, several studies have confirmed increased imaging resolution by using NIR‐II b (1500–1700 nm) emitting probes . Among these materials, Er 3+ ‐doped rare‐earth nanocrystals exhibiting efficient downshifted luminescence (1525 nm) in this wavelength region are applied for in vivo bioimaging –. However, one nonnegligible issue is that the previously reported excitation wavelength is mostly located at NIR‐I region such as 808 nm and 980 nm owing to the limited sensitizers (Yb 3+ , Nd 3+ ) .…”

Recent Advances on Activatable NIR‐II Fluorescence Probes for Biomedical Imaging

“…[77] The nanoprobe SPNP25 is achieved through blending a ClO − -responsive nonfullerene acceptor 3,9-bis(2-methylene- ( (Figure 7d-f). [78] In this system, excitation wavelength is used at 808 nm, i.e., in the absorption overlapping region, the NIR-II fluorescence of DCNPs is very weak because of the energy filtration by strong absorbance of Cy7.5 at 808 nm under the DCNPs. Under ClO − environment, the Cy7.5 is degraded and thus reversed the Images of e) 980 nm and f) 1180 nm and g) ratiometric (F 980 /F 1180 ) channels of microneedle patches for lipopolysaccharide-induced inflammation at each time points.…”