Unlocking the NIR‐II AIEgen for High Brightness through Intramolecular Electrostatic Locking

Abstract

Fluorescent imaging and biosensing in the near‐infrared‐II (NIR‐II) window holds great promise for non‐invasive, radiation‐free, and rapid‐response clinical diagnosis. However, it’s still challenging to develop bright NIR‐II fluorophores. In this study, we report a new strategy to enhance the brightness of NIR‐II aggregation‐induced emission (AIE) fluorophores through intramolecular electrostatic locking. By introducing sulfur atoms into the side chains of the thiophene bridge in TSEH molecule, the molecular motion of the conjugated backbone can be locked through intramolecular interactions between the sulfur and nitrogen atoms. This leads to enhanced NIR‐II fluorescent emission of TSEH in both solution and aggregation states. Notably, the encapsulated nanoparticles (NPs) of TSEH show enhanced brightness, which is 2.6‐fold higher than TEH NPs with alkyl side chains. The in vivo experiments reveal the feasibility of TSEH NPs in vascular and tumor imaging with a high signal‐to‐background ratio and precise resection for tiny tumors. In addition, polystyrene nanospheres encapsulated with TSEH are utilized for antigen detection in lateral flow assays, showing a signal‐to‐noise ratio 1.9‐fold higher than the TEH counterpart in detecting low‐concentration antigens. This work highlights the potential for developing bright NIR‐II fluorophores through intramolecular electrostatic locking and their potential applications in clinical diagnosis and biomedical research.

Quinoidal π-Bridges for a Fused-Ring Acceptor with Enhanced Near-Infrared-II Photothermal Therapy and Fluorescent Emission beyond 1500 nm

“…45 By modifying the NPs with RGD, selective uptake by 4T1 cells was improved, enabling effective targeting and imaging of tumors. 46 Upon intravenous injection of cRGD CNTIC-4F NPs (200 μL, 1 mg mL −1 ) into mice bearing a 4T1 tumor, the fluorescence intensity excited by a 1064 nm laser increases in the tumor region (Figures 4f and S14), peaking at 24 h postadministration before gradually declining due to liver metabolism and clearance of NPs (Figures 4g and S13). The infrared thermal images visualize a temperature rise from 35 to 50 °C at the tumor site within 5 min under excitation of a 1064 nm laser, consistent with the high PCE of CNTIC-4F NPs (Figure 4h,j).…”

“…cRGD (cyclic arginine–glycine–aspartic acid) was employed as a targeting ligand to enhance the specificity of CNTIC-4F NPs toward tumors . By modifying the NPs with RGD, selective uptake by 4T1 cells was improved, enabling effective targeting and imaging of tumors . Upon intravenous injection of cRGD CNTIC-4F NPs (200 μL, 1 mg mL –1 ) into mice bearing a 4T1 tumor, the fluorescence intensity excited by a 1064 nm laser increases in the tumor region (Figures f and S14), peaking at 24 h postadministration before gradually declining due to liver metabolism and clearance of NPs (Figures g and S13).…”