Ultrabright Föster Resonance Energy Transfer Nanovesicles: The Role of Dye Diffusion

Abstract

The development of contrast agents based on fluorescent nanoparticles with high brightness and stability is a key factor to improve the resolution and signal-to-noise ratio of current fluorescence imaging techniques. However, the design of bright fluorescent nanoparticles remains challenging due to fluorescence self-quenching at high concentrations. Developing bright nanoparticles showing FRET emission adds several advantages to the system, including an amplified Stokes shift, the possibility of ratiometric measurements, and of verifying the nanoparticle stability. Herein, we have developed Forster resonance energy transfer (FRET)-based nanovesicles at different dye loadings and investigated them through complementary experimental techniques, including conventional fluorescence spectroscopy and super-resolution microscopy supported by molecular dynamics calculations. We show that the optical properties can be modulated by dye loading at the nanoscopic level due to the dye's molecular diffusion in fluid-like membranes. This work shows the first proof of a FRET pair dye's dynamism in liquid-like membranes, resulting in optimized nanoprobes that are 120-fold brighter than QDot 605 and exhibit >80% FRET efficiency with vesicle-to-vesicle variations that are mostly below 10%.

Quatsomes Loaded with Squaraine Dye as an Effective Photosensitizer for Photodynamic Therapy

“…To overcome this drawback, a promising approach is represented by the incorporation into nanoparticle systems to shield its hydrophobicity, prevent the formation of dye aggregates, and improve solubility in physiological conditions [ 24 , 26 ]. Quatsomes (QS) nanovesicles have shown successful results incorporating different cyanine dyes [ 42 , 54 , 55 , 56 , 57 ], demonstrating long-term stability and biocompatibility. Thus, as a first trial, we prepared Br-Sq-C4-loaded quatsomes (QS).…”

Nanotherapeutic Heterogeneity: Sources, Effects, and Solutions

“…In the same platform, we also observed greater size heterogeneity at higher dye contents, further emphasizing the need for uniform dye loading. [219] Even if all nanoparticles in a heterogenous mixture were loaded with exactly the same number of dyes, the nanoparticles' propensity to retain these labels will likely vary, as dye retention diverges significantly between nanotherapeutic batches with even slightly different bulk properties. [160,218,220] Finally, the type and amount of dye loaded can directly influence nanoparticles' cellular uptake and therefore likely also their pharmacokinetics and biodistribution.…”

Aggregates of Cyanine Dyes: When Molecular Vibrations and Electrostatic Screening Make the Difference

“…Cyanines are a widespread family of dyes, constituted by heterocyclic electron donors or acceptor groups linked through a polymethinic bridge. , Cyanines are of interest for several applications, including photovoltaics, bioimaging, − phototherapy, − optical devices, , sensors, etc. The tendency of cyanines to self-organize in aggregates is known since 1937 when Jelley and Scheibe first described the formation of cyanine aggregates in solution. , The photophysics of cyanine aggregates strongly depends on the details of the molecular packing, which, in turn, are affected by several factors, including the length of the polymethinic bridge, the presence of non conjugated alkyl chains and their length, the environment (including the presence of additives), etc. − The possibility to widely tune the material properties makes cyanine aggregates extremely promising for applications in photonics, electronics, imaging, etc. − A robust theoretical approach must therefore be developed to relate the intriguing properties of cyanine aggregates to their supramolecular structure.…”

“…Cyanines are a widespread family of dyes, constituted by heterocyclic electron donors or acceptor groups linked through a polymethinic bridge. 1 , 2 Cyanines are of interest for several applications, including photovoltaics, 3 bioimaging, 4 − 7 phototherapy, 8 − 10 optical devices, 11 , 12 sensors, 13 etc. The tendency of cyanines to self-organize in aggregates is known since 1937 when Jelley and Scheibe first described the formation of cyanine aggregates in solution.…”