Aggregation of Amphiphilic Carbocyanines: Fluorination Favors Cylindrical Micelles over Bilayered Tubes

Self-Assembly of a Perfluorinated Amphiphilic Cyanine Dye into Branched Tubular J-Aggregates

The self-assembly process is governed by the individual constituents of molecules through precise non-covalent interactions. Amphiphilic cyanines are intriguing in supramolecular chemistry due to the large polarizability of their delocalized π-electron systems, their tuneable optical properties and their ability to form well-defined self-assembled structures in different media. Here we present the synthesis of a novel tetrahydroxy amphiphilic carbocyanine dye with perfluoro alkylated chains -(CH2)2-(CF2)5-CF3 as hydrophobic segments and aminoproanediol as hydrophilic segment. The target molecule was synthesized in a multi-step process, which illustrates the complexity and precision required to achieve the desired structure. This study focuses on the comparison of the influence of C8H17 and C8H4F13 tails and the effects of carboxylated and non-ionic aminopropanediol head groups as substituents on self-assembly of the TBC dye. Absorption and fluorescence measurements show similar spectroscopic properties to cyanine dyes studied previously. Cryogenic transmission electron microscopy (cryo-TEM) reveals formation of multiple supramolecular aggregates. As supramolecular assembly is very sensitive to sample preparation, multilamellar or multivesicular vesicles are obtained preferentially in vigorously vortexed solutions. Moreover, time-dependent tube formation was observed in gently mixed solutions. Thereby, we could follow the growing mechanism of the unprecedented Y-junctions of supramolecular tubes.

Tailoring Indocyanine Green J-Aggregates for Imaging, Cancer Phototherapy, and Drug Delivery: A Review

Indocyanine green J-aggregates (ICG-Jagg) have emerged as a significant subject of interest in biomedical applications due to their unique optical properties, tunable size, and excellent biocompatibility. This comprehensive review aims to provide an in-depth exploration of ICG-Jagg, with a focus on elucidating the diverse facets of their preparation and the factors that influence the preparation process. Additionally, the review discusses their applications in biomedical diagnostics, such as imaging and contrast agents, as well as their utilization in drug delivery and various phototherapeutic interventions.

The Pursuit of Shortwave Infrared-Emitting Nanoparticles with Bright Fluorescence through Molecular Design and Excited-State Engineering of Molecular Aggregates

Shortwave infrared (SWIR) fluorescence detection gradually becomes a pivotal real-time imaging modality, allowing one to elucidate biological complexity in deep tissues with subcellular resolution. The key challenge for the further growth of this imaging modality is the design of new brighter biocompatible fluorescent probes. This review summarizes the recent progress in the development of organic-based nanomaterials with an emphasis on new strategies that extend the fluorescence wavelength from the near-infrared to the SWIR spectral range and amplify the fluorescence brightness. We first introduce the most representative molecular design strategies to obtain near-infrared-SWIR wavelength fluorescence emission from small organic molecules. We then discuss how the formation of nanoparticles based on small organic molecules contributes to the improvement of fluorescence brightness and the shift of fluorescence to SWIR, with a special emphasis on the excited-state engineering of molecular probes in an aggregate state and spatial packing of the molecules in nanoparticles. We build our discussion based on a historical perspective on the photophysics of molecular aggregates. We extend this discussion to nanoparticles made of conjugated polymers and discuss how fluorescence characteristics could be improved by molecular design and chain conformation of the polymer molecules in nanoparticles. We conclude the article with future directions necessary to expand this imaging modality to wider bioimaging applications including single-particle deep tissue imaging. Issues related to the characterization of SWIR fluorophores, including fluorescence quantum yield unification, are also mentioned.