Silole‐Based Red Fluorescent Organic Dots for Bright Two‐Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging

Abstract

Robust luminescent dyes with efficient two-photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation-caused quenching. In this work, a red fluorescent silole, 2,5-bis[5-(dimesitylboranyl)thiophen-2-yl]-1-methyl-1,3,4-triphenylsilole ((MesB)2 DTTPS), is synthesized and characterized. (MesB)2 DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation-enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2 DTTPS within lipid-PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two-photon absorption cross section of 3.43 × 10(5) GM, which yields a two-photon action cross section of 1.09 × 10(5) GM. These (MesB)2 DTTPS dots show good biocompatibility and are successfully applied to one-photon and two-photon fluorescence imaging of MCF-7 cells and two-photon in vivo visualization of the blood vascular of mouse muscle in a high-contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network.

Organic Dots Based on AIEgens for Two‐Photon Fluorescence Bioimaging

“…Various functionalized siloles have been studied for the applications in optoelectronic devices, chemical sensors, bioprobes, etc . Recently, by rational design, a red fluorescent silole derivative, 2,5‐bis[5‐(dimesitylboranyl)thiophen‐2‐yl]‐1‐methyl‐1,3,4‐triphenylsilole ((MesB) 2 DTTPS), containing (dimesitylboranyl)thiophen‐2‐yl groups at the 2,5‐positions of central silole core was prepared ( Figure ) . The incorporation of (dimesitylboranyl)thiophen‐2‐yl groups induces electronic donor–acceptor interaction between silole and thiophen‐2‐yl units, which gives rise to good red fluorescence and two‐photon absorption properties.…”

“…Molecular structure and X‐ray single‐crystal structure of (MesB) 2 DTTPS (thermal ellipsoids set at 50% probability). Reproduced with permission . Copyright 2016, Wiley‐VCH.…”

“…E) MCF‐7 cell viabilities after incubation with (MesB) 2 DTTPS‐Tat dots for 24 and 48 h at different concentrations. Reproduced with permission . Copyright 2016, Wiley‐VCH.…”

“…(MesB) 2 DTTPS dots were excited at 820 nm, and the emitted light was detected through a 595/30 nm filter. Reproduced with permission . Copyright 2016, Wiley‐VCH.…”

Ultrasmall Organic Nanoparticles with Aggregation-Induced Emission and Enhanced Quantum Yield for Fluorescence Cell Imaging

“…21,22 Encapsulation of organic dye molecules into nanoparticles (NPs) may afford a promising strategy to extend the circulation life-time as particle-based agents and reduce the potential cytotoxicity. 23 However, the fluorescence intensity of conventional fluorophores tends to decrease when they are in in close contact; a common phenomenon known as aggregation-caused quenching (ACQ), which presents a dilemma for conventional fluorophores used in biomedical imaging. 24 Recently, opposite to the aforementioned ACQ effect, fluorescent molecules with aggregation-induced emission (AIE) feature, that is, the compound is non-emissive in solution but highly fluorescent once in its aggregated state, have been widely investigated for bio-imaging.…”