Design, Synthesis, and Application of a Small Molecular NIR-II Fluorophore with Maximal Emission beyond 1200 nm

Abstract

Small molecular fluorophores in the second near-infrared window (NIR-II) have aroused much interest because of their excellent performance. Herein, a new small molecular NIR-II fluorophore, FM1210, with maximal emission beyond 1200 nm is reported. Compared to the corresponding control fluorophore CF1065, FM1210 exhibits an increase of 145 nm in the emission maximum, which is ascribed to the simultaneous introduction of both a Se atom and amino groups into the benzo[1,2-c:4,5-c′]bis([1,2,5]thiadiazole) skeleton. This large increase in the maximal emission enables FM1210 to be capable of in vivo imaging with lower autofluorescence, higher signal-to-background ratio, and better resolution. Moreover, nanosized FM1210 encapsulated in liposomes possesses passive targeting ability and good water solubility, and is suitable for imaging a tumor and even its vasculature with high signal-to-background ratio.

Enlarging the Reservoir: High Absorption Coefficient Dyes Enable Synergetic Near Infrared‐II Fluorescence Imaging and Near Infrared‐I Photothermal Therapy

“…As shown in Figure 4b, owing to the introduction of two DPP units, TDADT NPs displayed significantly redshifted maximum absorption (838 vs 758 nm) and emission (1275 vs 1114 nm) peaks than that of TADAT NPs. Notably, the maximum emission wavelength of TDADT NPs is located at 1275 nm, which is among the longest ones for BBTD‐based small molecular dyes, [ 14 ] giving lower autofluorescence, higher signal‐to‐background ratio, and better spatial resolution in vivo imaging. The NIR‐II QY of TADAT and TDADT NPs is determined to be 0.2% and 0.1%, respectively, under 808 nm excitation using IR‐26 dye (QY = 0.5% in dichloroethane) as a reference (Figure 4c).…”

“…[ 19 ] It should be noted that the QY of 0.1% for TDADT NPs is one of the highest reported as far with a long emission wavelength (1275 nm) and high ε of >2.0 × 10 5 L mol −1 cm −1 . [ 14 ] Moreover, the NPs display excellent photostability as the negligible absorption intensity variation upon continuous 808 nm laser irradiation (Figure S16, Supporting Information). Then we evaluated the NIR‐II imaging qualities of the NPs.…”

“…Particularly, TDADT with two DPP units shows a long emission peak at 1275 nm, among the highest ones reported. [ 14 ] Notably, TADAT and TDADT reveal the fluorescence QY of 0.2% and 0.1% and photothermal conversion efficiency (PCE) of 64.3% and 60.4%, respectively. The better photophysical properties of the TDADT molecule motivate us to apply it for NIR‐II fluorescence‐guided surgery and PTT of tumors.…”

Activatable NIR‐II Fluorescent Probes Applied in Biomedicine: Progress and Perspectives

“…With the continuous emergence of excellent NIR‐II AFPs, the application of NIR‐II biological imaging technology in biomedical field has made considerable progress. Here, certain significant researches that associated with NIR‐II bioimaging of NIR‐II AFPs are presented, including precise tissue bioimaging, [90–94] dynamic bioimaging for monitoring [95–98] and multiplexed bioimaging [99–102] …”

“…Wang et al. designed a novel organic fluorophore FM1210 by simultaneously introducing both amino groups and a Se atom into the benzo[1,2‐c : 4,5‐c′]bis([1,2,5]thiadiazole) (BBTD) framework [93] . In their research, NIR‐II bioimaging of tumors and tumor vasculature in mice was acquired by utilizing FM1210 encapsulated in liposomes (FM1210‐NPs) (Figure 6).…”