Near‐infrared fluorophores with absolute aggregation‐caused quenching and negligible fluorescence re‐illumination for in vivo bioimaging of nanocarriers

Abstract

Environment-responsive fluorophores with aggregation-caused quenching (ACQ) properties have been applied to track nanocarriers with reduced artefacts caused by unbound or free fluorophores but suffer from incomplete fluorescence quenching and significant re-illumination, which undermine bioimaging accuracy. Herein, through structural modifications to reinforce the hydrophobicity, planarity and rigidity of fluorophores with an aza-BODIPY framework, probes featuring absolute ACQ (aACQ) and negligible re-illumination are developed and evaluated in various nanocarriers. aACQ probes, FD-B21 and FD-C7, exhibit near-infrared emission, high quantum yield, photostability, water sensitivity, and negligible re-illumination in blood, plasma and 1% Tween-80 in contrast to ACQ probe P2 and conventional probe DiR. All nanocarriers can be labeled efficiently by the tested fluorophores. Polymeric micelles (PMs) labeled by different aACQ probes manifest similar biodistribution patterns, which however differ from that of DiR-labeled PMs and could be ascribed to the appreciable re-illumination of DiR. Significantly lower re-illumination is also found in aACQ probes (2%-3%) than DiR (20%-40%) in Caco-2, Hela, and Raw264.7 cells. Molecular dynamics simulations unravel the molecular mechanisms behind aggregation and re-illumination, supporting the hypothesis of planarity dependency. It is concluded that aACQ fluorophores demonstrate excellent water sensitivity and negligible fluorescence re-illumination, making themselves useful tools for more accurate bioimaging of nanocarriers.

Selection of an aggregation-caused quenching-based fluorescent tracer for imaging studies in nano drug delivery systems

“…A detailed step-bystep description and discussion of in vivo live imaging has been published. 49 Conclusions ACQ fluorescent dyes have an "ON → OFF" signal conversion mode, which has broad application prospects in the field of NDDSs. Our previous studies have demonstrated the application value of ACQ dye P2; however, multiple components in the biological environment may cause the re-illumination of the quenched fluorescent aggregates.…”

Electrosprayed Eudragit RL100 nanoparticles with Janus polyvinylpyrrolidone patches for multiphase release of paracetamol

“…Pharmaceutics is an interdisciplinary field in which many subjects play important roles. [1][2][3][4][5] Particularly in this nano era, nanotechniques and the corresponding complex nanostructures they produce continuously exhibit the capability to generate novel nano-drug delivery systems (DDSs). [6][7][8][9] The three directions of nanoscience, i.e., "small size, order, and structure", aim to produce all kinds of nanomaterials with increasingly smaller sizes to create arrays of nanoproducts for functional applications and to generate new complicated nanostructures and nanodevices for tailoring functional performances.…”

Matthew effect: General design strategy of ultra‐fluorogenic nanoprobes with amplified dark–bright states in aggregates

“…In this regard, we consider aggregation, a spontaneous phenomenon of hydrophobic molecules in aqueous systems, will be an effective solution to increase tetrazine-chromophore proximity and interactions, enhancing tetrazine quenching effects. [23,53] However, most conventional planar fluorophores suffer from aggregation-caused quenching (ACQ) effect, [54][55][56] which diminishes post-click turn-on emission in aggregates, making it difficult to apply this aggregation strategy for fluorogenic probe designs. Therefore, we focused on aggregation-induced emission luminogens (AIEgens), a series of dyes that exhibit weak emission in dilute solutions but significantly enhanced emission in the aggregate state, to achieve this strategy.…”