Acceptor engineering for NIR-II dyes with high photochemical and biomedical performance

Abstract

It is highly important and challenging to develop donor-acceptor-donor structured small-molecule second near-infrared window (NIR-II) dyes with excellent properties such as water-solubility and chem/photostability. Here, we discovery an electron acceptor, 6,7-di(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TQT) with highest stability in alkaline conditions, compared with conventional NIR-II building block benzobisthiadiazole (BBT) and 6,7-diphenyl-[1,2,5] thiadiazolo[3,4-g]quinoxaline (PTQ). The sulfonated hydrophilic dye, FT-TQT, is further synthesized with 2.13-fold increased quantum yield than its counterpart FT-BBT with BBT as acceptor. FT-TQT complexed with FBS is also prepared and displays a 16-fold increase in fluorescence intensity compared to FT-TQT alone. It demonstrates real-time cerebral and tumor vessel imaging capability with µm-scale resolution. Dynamic monitoring of tumor vascular disruption after drug treatment is achieved by NIR-II fluorescent imaging. Overall, TQT is an efficient electron acceptor for designing innovative NIR-II dyes. The acceptor engineering strategy provides a promising approach to design next generation of NIR-II fluorophores which open new biomedical applications.

J-aggregates albumin-based NIR-II fluorescent dye nanoparticles for cancer phototheranostics

“…Small-molecule organic fluorophores with great biocompatibility have proven to be attractive candidates for clinical phototheranostics [ 5 ]. Compared with the first near-infrared biological window (NIR-I), fluorophores imaged in the second window (NIR-II, 1000–1700 ​nm) exhibit a higher temporal and spatial resolution and tissue penetration depth [ [6] , [7] , [8] , [9] , [10] , [11] ]. Polymethine cyanine-based dye IR1061 (λem ​= ​1061 ​nm in methylene chloride) is a typical small-molecule organic fluorophore whose emission wavelength is in the NIR-II window, which is composed of two heterocyclic terminal groups connected by the polymethine linker [ 12 ].…”

Cyclic enhancement of hypoxic microenvironment via an intelligent nanoamplifier for activated NIR-II fluorescence/photoacoustic imaging-guided precise synergistic therapy

“…Admittedly, excellent imaging performance for nanotheranostics should possess unprecedented tissue penetration, spatiotemporal resolution, and good biosafety [ 4 ]. Fluorescence imaging in the second near-infrared window (NIR-II FL, 1000–1700 ​nm) has received increasing attention because of its minimal photon scattering, absorption, and negligible tissue auto-fluorescence [ 5 , 6 ]. Remarkably, activatable NIR-II FL nanoprobes that uncage NIR-II FL signals merely in responding to disease-related biomarkers can effectively boost the detection sensitivity and specificity [ 7 , 8 ].…”

Water-Dispersible Activatable Nanoprobe for Detecting Cadmium-Ion-Induced Oxidative Stress in Edible Crops via Near-Infrared Second-Window Fluorescence Imaging

“…Fluorescence imaging is a noninvasive method, − which is conducive to detecting and monitoring the variation of in situ biomarkers in a real-time manner in plants. − As for in vivo fluorescence imaging in plants, the imaging quality in the shorter wavelength range (e.g., visible light (400–700 nm) or NIR-I range (700–900 nm)) is usually compromised or eroded because such pigments as chlorophylls, anthocyanins, and carotenoids in plants usually have absorptions in the visible-light wavelength range and exhibit fluorescence in the visible-light or NIR-I wavelength range. − However, near-infrared second window (NIR-II, emission: 900–1700 nm) fluorescence imaging can achieve much superior imaging performance, − owing to no interference from plant-related pigments in the NIR-II wavelength range.…”