Incorporation of Planar Blocks into Twisted Skeletons: Boosting Brightness of Fluorophores for Bioimaging beyond 1500 Nanometer

Abstract

The brightness of organic fluorescence materials determines their resolution and sensitivity in fluorescence display and detection. However, strategies to effectively enhance the brightness are still scarce. Conventional planar π-conjugated molecules display excellent photophysical properties as isolated species but suffer from aggregation-caused quenching effect when aggregated owing to the cofacial π–π interactions. In contrast, twisted molecules show high photoluminescence quantum yield (ΦPL) in aggregate while at the cost of absorption due to the breakage in conjugation. Therefore, it is challenging to integrate the strong absorption and high solid-state ΦPL, which are two main indicators of brightness, into one molecule. Herein, we propose a molecular design strategy to boost the brightness through the incorporation of planar blocks into twisted skeletons. As a proof-of-concept, twisted small-molecule TT3-oCB with larger π-conjugated dithieno­[3,2-b:2′,3′-d]­thiophene unit displays superb brightness at the NIR-IIb (1500–1700 nm) than that of TT1-oCB and TT2-oCB with smaller thiophene and thienothiophene unit, respectively. Whole-body angiography using TT3-oCB nanoparticles presents an apparent vessel width of 0.29 mm. Improved NIR-IIb image resolution is achieved for femoral vessels with an apparent width of only 0.04 mm. High-magnification through-skull microscopic NIR-IIb imaging of cerebral vasculature gives an apparent width of ∼3.3 μm. Moreover, the deeply located internal organ such as bladder is identified with high clarity. The present molecular design philosophy embodies a platform for further development of in vivo bioimaging.

Biologically Excretable Aggregation‐Induced Emission Dots for Visualizing Through the Marmosets Intravitally: Horizons in Future Clinical Nanomedicine

“…To detect the excretion of AIEgens with aliphatic chains in vivo directly, we selected four other typical kinds of NIR-II AIE fluorophores in which the two possess aliphatic chains (2TT-oC610B [13] and TT3-oCB [24] ) but the others (TQ-BPN [14] and BPN-BBTD [11] ) do not. With OTPA-BBT (in this work), we PEGylated all the five kinds of AIEgens via Pluronic F127 (Figure 2E) and intravenously injected them to the mice respectively (10 mg kgBW −1 ).…”

Biologically excretable AIE dots for visualizing through the marmosets intravitally: horizons in future clinical nanomedicine

“…To detect the excretion of AIEgens with aliphatic chains in vivo directly, we selected four other typical kinds of NIR-II AIE fluorophores in which the two possess aliphatic chains (2TT-oC26B [13] and TT3-oCB [24] ) but the others (TQ-BPN [14] and BPN-BBTD [11] ) do not. With OTPA-BBT (in this work), we PEGylated all the five kinds of AIEgens via Pluronic F127 (Figure 2E) and intravenously injected them to the mice respectively (10 mg kgBW −1 ).…”

Donor/π-Bridge Manipulation for Constructing a Stable NIR-II Aggregation-Induced Emission Luminogen with Balanced Phototheranostic Performance

“…It is found that the introduce of congested 3,4-ethoxylene dioxythiophene (EDOT) or ortho-alkylated thiophene can increase the torsion angle between D/π-bridge and A as well as distort the conjugated backbone, thus boosting the fluorescence quantum yield (QY) in aggregate state. [43][44][45] By contrast, the bared thiophene or meta-alkylated thiophene can hardly constrain the reciprocal intermolecular interactions even further installing more distorted rotors. 46,47 Notwithstanding those intriguing advancement, much effort on developing novel D/π-bridge to enrich the library of NIR-II AIE theranostic agent deserves to be devoted.…”