Synthesis of Silicon-Substituted Hemicyanines for Multimodal SWIR Imaging

Phospha-RosIndolizine Dye with Shortwave Infrared (SWIR) Absorption and Emission

Shortwave infrared (SWIR, 1000-1700 nm) absorbing and emitting dyes are needed for infrared diodes and sensors used in a wide variety of industrial and medical applications. Herein, an electron-withdrawing phosphine oxide (P═O) substituted xanthene is coupled with strong indolizine donors to produce a SWIR absorbing (λabs = 1294 nm in DCM) and emitting (λemis = 1450 nm in DCM) dye called PRos1450. The unique properties of this dye are characterized via photophysical, electrochemical, and computational analyses.

A Dual-Function Hemicyanine Material with Highly Efficient Photothermal and Photodynamic Effect Used for Tumor Therapy

Small molecular organic optical agents with synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT), hold credible promise for anti-tumor therapy by overcoming individual drawbacks and enhancing photon utilization efficiency. However, developing effective dual-function PTT-PDT photosensitizers (PSs) for efficient synergistic phototherapy remains challenging. Here, a benz[c,d]indolium-substituted hemicyanine named Rh-BI, which possesses a high photothermal conversion efficiency of 41.67% by exhaustively suppressing fluorescence emission, is presented. Meanwhile, the rotating phenyl group at meso-site induces charge recombination to enhance the molar extinction coefficient up to 13.58 × 104 M-1cm-1, thereby potentiating the photodynamic effect. Under 808 nm irradiation, Rh-BI exhibits significant phototoxicity in several cancer cell types in vitro with IC50 values as low as ≈0.5 µM. Moreover, treatment of 4T1 tumor-bearing mice with Rh-BI under laser irradiation successfully inhibits tumor growth. In a word, an effective strategy is developed to build PTT-PDT dual-functional optical materials based on hemicyanine backbone for tumor therapy by modulating conjugation system interaction to adjust the energy consumption pathway.

Chemical Approaches to Optimize the Properties of Organic Fluorophores for Imaging and Sensing

Organic fluorophores are indispensable tools in cells, tissue and in vivo imaging, and have enabled much progress in the wide range of biological and biomedical fields. However, many available dyes suffer from insufficient performances, such as short absorption and emission wavelength, low brightness, poor stability, small Stokes shift, and unsuitable permeability, restricting their application in advanced imaging technology and complex imaging. Over the past two decades, many efforts have been made to improve these performances of fluorophores. Starting with the luminescence principle of fluorophores, this review clarifies the mechanisms of the insufficient performance for traditional fluorophores to a certain extent, systematically summarizes the modified approaches of optimizing properties, highlights the typical applications of the improved fluorophores in imaging and sensing, and indicates existing problems and challenges in this area. This progress not only proves the significance of improving fluorophores properties, but also provide a theoretical guidance for the development of high-performance fluorophores.

Activity-Based Photoacoustic Probes for Detection of Disease Biomarkers beyond Oncology

The earliest activity-based photoacoustic (PA) probes were developed as diagnostic agents for cancer. Since this seminal work over a decade ago that specifically targeted matrix metalloproteinase-2, PA instrumentation, dye platforms, and probe designs have advanced considerably, allowing for the detection of an impressive list of cancer types. However, beyond imaging for oncology purposes, the ability to selectively visualize a given disease biomarker, which can range from aberrant enzymatic activity to the overproduction of reactive small molecules, is also being exploited to study a myriad of noncancerous disease states. In this review, we have assembled a collection of recent papers to highlight the design principles that enable activity-based sensing via PA imaging with respect to biomarker identification and strategies to trigger probe activation under specific conditions.

Dihydroxanthene-Based Near-infrared Fluorescent Probes for Monitoring Mitochondrial Viscosity in Living Cells and Mice

Aberrant mitochondrial viscosity is closely associated with many diseases and cellular malfunctions. Thus, the development of reliable methods for monitoring mitochondrial viscosity variations has attracted considerable attention. Herein, through stepwise structural modulation of the dihydroxanthene fluorophore (DHX), we developed three NIR fluorescent probes, named DHX-V-1-3, for detecting mitochondrial viscosity. Among them, DHX-V-3 displayed the highest signal-to-noise ratio (67-fold) for viscosity with outstanding selectivity and showed excellent mitochondria targeting and immobilization ability. At the cellular level, the DHX-V-3 probe was successfully applied to image the mitochondrial viscosity in live cells upon treatment with lipopolysaccharide (LPS) or nystatin. Moreover, benefiting from its NIR emission and the increased depth of tissue imaging, DHX-V-3 demonstrated the ability to visualize the increased viscosity in LPS-treated mice.