Controlling the packing arrangements of dyes is a facile way of tuning their photophysical and/or photochemical properties, thus enabling new sensing mechanisms for photofunctional tools. Here, we present a general and robust strategy toward water-stable J-aggregated dye-templated nanoassemblies by incorporating an amphiphilic diblock copolymer and a stimuli-responsive dye as the only two building components. An iodo-substituted boron dipyrromethene (BODIPY) was adopted as a template to direct the self-assembly of poly(ethylene glycol)-block-polycaprolactone (PEG−PCL), forming a core−shell nanoplate with slip-stacked BODIPYs as core surrounded by hydrophilic PEG shell. The self-assembled nanoplate is stable in cell culture medium and possesses a built-in stimuli-responsiveness that arises from BODIPY bearing meso-carboxylate protecting group, which is efficiently removed upon treatment with peroxynitrite. The resulting negative charges lead to rearrangement of dyes from J-stacking to nonstacking, which activates photoinduced singlet oxygen production from the nanoassemblies. The stimuli-activatable photosensitivity has been exploited for specific photodynamic ablation of activated RAW 264.7 cells with excessive endogenous peroxynitrite. In light of the generality of the sensing mechanism, the concept described herein will significantly expand the palette of design principles to develop diverse photofunctional tools for biological research and clinical needs.

The design of organic photothermal agents (PTAs) for in vivo applications face a demanding set of performance requirements, especially intense NIR-absorptivity and sufficient photobleaching resistance. J-aggregation offers a facile way to tune the optical properties of dyes, thus providing a general design platform for organic PTAs with the desired performance. Herein, we present a supramolecular strategy to build a water-stable, nonphotobleaching, and NIR-absorbing nano-PTA (J-NP) from J-aggregation of halogenated BODIPY dyes (BDP) for efficient in vivo photothermal therapy. Multiple intermolecular halogen-bonding and π–π stacking interactions triggered the formation of BDP J-aggregate, which adsorbed amphiphilic polymer chains on the surface to provide PEGylated sheetlike nano-J-aggregate (J-NS). We serendipitously discovered that the architecture of J-NS was remodeled during a long-time ultrafiltration process, generating a discrete spherical nano-J-aggregate (J-NP) with controlled size. Compared with J-NS, the remodeled J-NP significantly improved cellular uptake efficiency. J-aggregation brought J-NP striking photothermal performance, such as strong NIR-absorptivity, high photothermal conversion efficiency up to 72.0%, and favorable nonphotobleaching ability. PEGylation and shape-remodeling imparted by the polymer coating enabled J-NP to hold biocompatibility and stability in vivo, thereby exhibiting efficient antitumor photothermal activities. This work not only presents a facile J-aggregation strategy for preparing PTAs with high photothermal performance but also establishes a supramolecular platform that enables the appealing optical functions derived from J-aggregation to be applied in vivo.

A general approach toward highly fluorogenic probes across the visible spectrum for various analytes offers significant potential for engineering a wide range of bioprobes with diverse sensing and imaging functions. Here we show a facile and general strategy that involves introducing a new fluorogenic mechanism in boron dipyrromethene (BODIPY) dyes, based on the principle of stimuli-triggered dramatic reduction in the electron-withdrawing capabilities of the meso-substituents of BODIPYs. The fluorogenic mechanism has been demonstrated to be applicable in various BODIPYs with emission maxima ranging from green to far red (509, 585, and 660 nm), and the synthetic strategy allows access to a panel of highly fluorogenic bioprobes for various biomolecules and enzymes (HO, HS, and protease) via introducing specific triggering motifs. The potency of the general design strategy is exemplified by its application to develop a mitochondria-targeting far-red probe capable of imaging of endogenous HO in living cells.

Dye assemblies exhibit fascinating properties and performances, both of which depend critically on the mutual packing arrangement of dyes and on the supramolecular architecture. Herein, we engineered, for the first time, an intriguing chlorosome‐mimetic 2D crystalline J‐dimer lamellar structure based on halogenated dyes in aqueous media by employing two distinct orthogonal halogen‐bonding (XB) interactions. As the only building motif, antiparallel J‐dimer was formed and stabilized by single π‐stacking and dual halogen⋅⋅⋅π interactions. With two substituted halogen atoms acting as XB donors and the other two acting as acceptors, the constituent J‐dimer units were linked by quadruple highly‐directional halogen⋅⋅⋅halogen interactions in a staggered manner, resulting in unique 2D lamellar dye assemblies. This work champions and advances halogen‐bonding as a remarkably potent tool for engineering dye aggregates with a controlled molecular packing arrangement and supramolecular architecture.