Achieving J-aggregation of a molecule is a fascinating way to construct fluorescent imaging as well as photothermal therapy agents in the second near-infrared window. Modulation of the balance between intermolecular...
Due to the hydrophobicity of the cyanine dye and the huge conjugated plane, the cyanine dye is prone to H-aggregation in the aqueous solution, and the ultraviolet absorption is blue-shifted....
Most NIR-II fluorescent dyes, especially polymethine cyanine, face the inevitable self-quenching phenomenon in an aqueous solution. This unacceptable property has severely limited their application in high-resolution biological imaging. Here, a NIR-II macromolecular probe (MPAE) is synthesized through the structure modification of molecule probe and the covalent coupling of an amphiphilic polypeptide, which presents considerable biocompatibility and negligible systemic side effect. The molecule probe's stereo structure and the polymer's conjugation could effectively prevent the 𝝅-𝝅 stacking, thereby exhibiting excellent quenching resistance in aqueous solutions (absolute QY = 0.178%). This remarkable feature endows it with deeper tissue penetration than the clinically used indocyanine green (ICG) and high contrast brightness at the tumor site for the NIR-II fluorescence imaging. Based on the effective accumulation of tumor sites and considerable photothermal conversion efficiency (40.07%), the MPAE-NPS presents superior antitumor efficiency on breast tumor-bearing mice under the 1064 nm irradiation without rebound or recurrence. All these outstanding performances reveal the great promise of MPAE-NPS in Nano-drug delivery and imaging-assisted photothermal therapy in the NIR-II window.
With the continuous development of organic materials for optoelectronic devices and biological applications, J-aggregation has attracted a great deal of interest in both dye chemistry and supramolecular chemistry. Except for the characteristic red-shifted absorption and emission, such ordered head-to-tail stacked structures may be accompanied by special properties such as enhanced absorption, narrowed spectral bandwidth, improved photothermal and photodynamic properties, aggregation-induced emission enhancement (AIEE) phenomenon, and so forth. These excellent properties add great potential to J-aggregates for optical imaging and phototherapy in the near-infrared (NIR) region. Despite decades of development, the challenge of rationally designing the molecular structure to adjust intermolecular forces to induce J-aggregation of organic dyes remains significant. In this review, we discuss the formation of J-aggregates in terms of intermolecular interactions and summarize some recent studies on J-aggregation dyes for NIR imaging and phototherapy, to provide a clear direction and reference for designing J-aggregates of near-infrared organic dyes to better enable biological applications.
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