A novel aggregation‐induced emission fluorescent probe with large Stokes shift for sensitive detection of pH changes in live cells

Abstract

The detection of intracellular pH is crucial for elucidating the pathological process of cancers, as well as for medical diagnostic applications. Here, we developed an aggregation-induced emission active pH-responsive fluorescent probe (TPE-DCP) for sensitively detecting cell pH changes. The probe shows obvious pH-sensing properties at $615 nm, with a pKa value of 6.82 and a good linear pH response ranging from 8.5 to 4.5. TPE-DCP holds advantages such as excellent anti-interference performance, good photostability, and low cytotoxicity, and has been successfully used to image intracellular pH changes in cells.

Visualizing intracellular dynamics with AIE probes

“…Jia et al designed an AIE probe with a large stokes shift to detect intracellular pH changes. 24 The reported probe, TPE-DCP, displayed fluorescence enhancement in an acidic environment and a dramatic decrease in fluorescence in a basic environment. Intracellular pH detection from 4.5–8.5 by fluorescence enhancement was achieved in HepG2 cells where TPE-DCP displayed gradual red emission enhancement with the strongest signal at pH 4.5.…”

Donor–Acceptor–Donor Near-Infrared-II Aggregation-Induced Emission Luminogens (AIEgens) Encapsulated within Nanometer-Sized Exosomes for Tumor Imaging

“…Fluorescence imaging performed in the transparent second near-infrared (NIR-II, 1000–1700 nm) biowindow has recently been a powerful tool to directly visualize dynamic biological processes owing to its noninvasive damage control, real-time visualization, and high sensitivity and imaging resolution as well as deep tissue penetration and high signal-to-background ratio (SBR). − So far, tremendous fluorophores emitting within the NIR-II region, including inorganic and organic NIR-II fluorophores, have been reported for various biological imaging applications. − Notably, remarkable accomplishments have been made by organic NIR-II fluorophores due to their metal-free safety, ease of processability, and clinical translation. − However, when these inherent hydrophobic fluorophores were fabricated into nanoparticles (NPs) with an aggregated state for biological applications, they always suffer from a low NIR-II quantum yield (QY) because of the emission quenching resulting from the strong intermolecular interactions, termed as the aggregation-caused quenching (ACQ) effect. − Fortunately, as an alternative method, aggregation-induced emission (AIE), which was discovered by Tang et al, holds great potential to address the quenching problem. − To drive emission to the NIR-II window, AIE luminogens (AIEgens) are usually designed as donor–acceptor–donor (D–A–D) structures with typical molecular motors to suppresses the strong intermolecular interactions. − However, compared to the systematically well-explored near-infrared-I (NIR-I, 650–900 nm) AIEgens, the research on D–A–D-type NIR-II AIEgens received a snub, by contrast, owing to their lack of diversity and low AIE character (α AIE < 2, a value defined as the ratio of PL intensity at water fraction ( f w ) = 90% to that of f w = 0%), which has become a bottleneck in the bioimaging field. − …”

New pyrrolo[3,2‐b]pyrroles with AIE characteristics for detection of dichloromethane and chloroform

“…The ongoing development of new fluorescent dyes and their application as fluorescent probes containing pyrene [1][2][3][4] or tetraphenylethylene (TPE) [5][6][7][8] moieties has expanded the need for dyes with diverse spectral and physicochemical properties. Since 1,2,4,5-tetraaryl-1,4-dihydropyrrolo [3,2-b]pyrroles (TAPPs) were synthesized via a one-pot multicomponent reaction, this category of compound has attracted great attention due to their diverse selection of substituent groups, tunable electronic properties, and fantastic optical properties [9].…”