Molecular Design of NIR-II Polymethine Fluorophores for Bioimaging and Biosensing

Abstract

Organic polymethine fluorophores with emission in the NIR-II window (1000–1700 nm) are receiving enormous attention in biomolecular medicine and bioimaging, attributed to the high absorption coefficients, bright NIR-II emission, excellent biocompatibility, and molecule adjustability. Recently, researchers have devoted significant effort to designing and improving NIR-II polymethine fluorophores and making notable progress in the NIR-II fluorescence imaging performance. This review summarizes recent developments in the molecular engineering design mentality of polymethine fluorophores and probes and highlights their extensive bioimaging and biosensing applications. Furthermore, we elucidate the potential challenges and perspectives of these NIR-II polymethine dyes in chemical and biomedicine imaging, which may stimulate the further development of high-performance NIR-II polymethine dye contrast agents for their future clinical applications.

A Fast and Reversible Responsive Bionic Transmembrane Nanochannel for Dynamic Single-Cell Quantification of Glutathione

“…Upon experimental optimizations including a SiRh concentration of 1 mM (Figure S9) and incubation time of 2 h (Figure S10), the condensation reaction of SiRh with amine groups decreased the intensity of positive charges and thus weakened the ICR (blue curve). Considering the increase in contact angle experiments (from 53.8 ± 1.5° to 65.7 ± 1.8°) before and after SiRh modification (Figure S11), the increased surface hydrophobicity might be the reason for the reduced of surface charge. − In addition, the strong fluorescence of SiRh within the nanotip confirmed its successful modification (Figure c). The changes in the surface charge with each step of the modification were also verified by zeta potential measurements on the simulated surface of silica nanoparticles with the same treatment (Figure S12).…”

“…Stimuli-responsive small molecule probes endowed with structural diversity, high selectivity, sensitivity and good responsibility have shown promise for molecular recognition, biosensing and imaging. − Taking the purpose of precise quantification, they have also been synergized with the nanochannels to eliminate the probe diffusion during measurements. For instance, Li et al presented an NO gating system in a nanochannel of a polyethylene terephthalate membrane based on a spiro ring opening-closing reaction between o -phenylenediamine and NO, allowing for ionic NO biosensing .…”

Controlled In Situ Self-Assembly of Biotinylated Trans-Cyclooctene Nanoparticles for Orthogonal Dual-Pretargeted Near-Infrared Fluorescence and Magnetic Resonance Imaging

“…Stimuli-triggered in situ self-assembly (STAY) strategy, − which involves small-molecule probes with well-defined chemical structures and ultimately forms nanostructures when triggered by a stimulus, such as an enzyme, has shown potential for use in molecular imaging − and drug delivery. − The STAY strategy combines the good tissue penetration ability of small molecules with the long residence time of nanomaterials in tumors. − This facilitates bypassing the poor tumor penetration of nanoparticles and fast washout of small molecules from the tumor tissues. Therefore, the STAY strategy has the potential to enhance the delivery and accumulation of probes in the target tissue for imaging or therapy.…”

NIR-II Light Excited Heptamethine Cyanine/Prodrug/Albumin Nanoparticles for Photothermal/Photodynamic/Chemo Combination Therapy

“…Additionally, the NIR-II region exhibits lower tissue autofluorescence, which leads to improved signal-to-noise ratios and enhances the efficiency of imaging and therapeutic applications. This reduction in autofluorescence enables more accurate and precise detection and treatment of target tissues. − However, the development of high-performance NIR-II fluorophores still faces constraints such as a narrow HOMO–LUMO gap, poor biocompatibility, and inadequate water solubility. These limitations result in the weak NIR-II fluorescence brightness and signal when applied in vivo.…”