The Self-assembly of Cyanine Dyes for Biomedical Application In Vivo

Intriguing H-Aggregates of Heptamethine Cyanine for Imaging-Guided Photothermal Cancer Therapy

Organic small-molecule-based photothermal agents such as cyanine dyes have received increasing attention in developing novel cancer therapies with potential clinical utility but suffer from poor stability, low photothermal efficiency, and limited accumulation at tumor sites in molecular forms. Self-assembly of small-molecule dyes into supramolecular assemblies may address these concerns by controlling the molecular organization of dye monomers to form structures of a higher order. Among them, H-aggregates of dyes favor face-to-face contacts with strongly overlapping areas, which always have a negative connotation to exhibit low or no fluorescence in most cases but may emanate energy in nonradiative forms such as heat for photothermal cancer therapy applications. Here, the synergistic self-assembly of cyanine dyes into H-aggregates is developed as a new supramolecular strategy to fabricate small-molecule-based photothermal nanomaterials. Compared to the free cyanine dyes, the H-aggregates assembled from pyrene or tetraphenylethene (TPE) conjugating cyanine exhibit the expected absorption spectral blue shift and fluorescence self-quenching but unique photothermal properties. Remarkably, the obtained H-aggregates are saucer-shaped nanoparticles that exhibit passive tumor-targeting properties to induce imaging-guided photothermal tumor ablation under irradiation. This supramolecular strategy presented herein may open up new opportunities for constructing next-generation small-molecule-based self-assembly nanomaterials for PTT cancer therapy in clinics.

Supramolecular Nanodiscs Self-Assembled from Non-Ionic Heptamethine Cyanine for Imaging-Guided Cancer Photothermal Therapy

Supramolecular nanomedicines, which use supramolecular design to improve the precision and effectiveness of pharmaceutical practice and optimize pharmacokinetic profiles, have gathered momentum to battle cancer and other incurable diseases, for which traditional small-molecular and macromolecular drugs are less effective. However, the lack of clinical approval of supramolecular assembly-based medicine underscores the challenges facing this field. A 2D nanodisc-based supramolecular structure is formed by a non-ionic heptamethine cyanine (Cy7) dye, which generates fluorescence self-quenching but unique photothermal and photoacoustic properties. These Cy7-based supramolecular nanodiscs exhibit passive tumor-targeting properties to not only visualize the tumor by near-infrared fluorescence imaging and photoacoustic tomography but also induce photothermal tumor ablation under irradiation. Due to the nature of organic small molecule, they induce undetectable acute toxicity in mice and can be eliminated by the liver without extrahepatic metabolism. These findings suggest that the self-assembling cyanine discs represent a new paradigm in drug delivery as single-component supramolecular nanomedicines that are self-delivering and self-formulating, and provide a platform technology for synergistic clinical cancer imaging and therapy.