Amphiphilicity-Controlled Polychromatic Emissive Supramolecular Self-Assemblies for Highly Sensitive and Efficient Artificial Light-Harvesting Systems

Regulation of Fluorescence and Self-assembly of a Salicylaldehyde Azine-Containing Amphiphile by Pillararene

Regulation of fluorescence and self-assembly of a salicylaldehyde azine-containing amphiphile by a water-soluble pillar[5]arene via host-guest recognition in water was realized. The fluorescence and the self-assembled aggregates of the bola-type amphiphile G can be tailored by adding different amounts of water-soluble pillar[5]arene (WP5). In addition, the emission property and self-assembly behavior of G and WP5 are responsive to pH conditions. Furthermore, the fluorescence emission property of G and the regulation by WP5 or pH conditions was applied as information encryption material, rewritable paper, and erasable ink. We believe that this fluorescence regulation strategy is promising for the construction of advanced fluorescent organic materials.

Cucurbit[8]uril Confinement-Based Secondary Coassembly for High-Efficiency Phosphorescence Energy Transfer Behavior

Aqueous supramolecular long-lived near-infrared (NIR) material is highly attractive but still remains great challenge. Herein, we report cucurbit[8]uril confinement-based secondary coassembly for achieving NIR phosphorescence energy transfer in water, which is fabricated from dicationic dodecyl-chain-bridged 4-(4-bromophenyl)-pyridine derivative (G), cucurbit[8]uril (CB[8]), and polyelectrolyte poly(4-styrene-sulfonic sodium) (PSS) via the hierarchical confinement strategy. As compared to the dumbbell-shaped G, the formation of unprecedented linear polypseudorotaxane G⊂CB[8] with nanofiber morphology engenders an emerging phosphorescent emission at 510 nm due to the macrocyclic confinement effect. Moreover, benefiting from the following secondary assembly confinement, such tight polypseudorotaxane G⊂CB[8] can further assemble with anionic polyelectrolyte PSS to yield uniform spherical nanoparticle, thereby significantly strengthening phosphorescence performance with an extended lifetime (i.e., 2.39 ms, c.f., 45.0 μs). Subsequently, the organic dye Rhodamine 800 serving as energy acceptor can be slightly doped into the polyelectrolyte assembly, which enables the occurrence of efficient phosphorescence energy transfer process with efficiency up to 80.1% at a high donor/acceptor ratio, and concurrently endows the final system with red-shifted and long-lived NIR emission (710 nm). Ultimately, the as-prepared assembly is successfully exploited as versatile imaging agent for NIR window labeling and detecting in living cells.

Three-step cascaded artificial light-harvesting systems with tunable efficiency based on metallacycles

It is still challenging to develop multi-step cascaded artificial light-harvesting systems (ALHSs) with tunable efficiency. Here, we designed novel cascaded ALHSs with AIE-active metallacycles as the light-harvesting antenna, Eosin Y (ESY) and sulforhodamine 101 (SR101) as conveyors, near-infrared emissive chlorin-e6 (Ce6) as the final acceptor. The close contact and fair spectral overlap between donor and acceptor molecules at each level ensured the efficient sequential three-step energy transfer. The excited energy was sequentially and efficiently funneled to Ce6 along the cascaded line MTPEPt1 → ESY → SR101 → Ce6. Additionally, a unique strategy for regulating the efficiency of ALHS was illustrated by adjusting hydrophilic and hydrophobic interactions.

A metal-organic framework-based fluorescence resonance energy transfer nanoprobe for highly selective detection of Staphylococcus Aureus

Survival and infection of pathogenic bacteria, such as Staphylococcus aureus (S. aureus), pose a serious threat to human health. Efficient methods for recognizing and quantifying low levels of bacteria are imperiously needed. Herein, we introduce a metal-organic framework (MOF)-based fluorescence resonance energy transfer (FRET) nanoprobe for ratiometric detection of S. aureus. The nanoprobe utilizes blue-emitting 7-hydroxycoumarin-4-acetic acid (HCAA) encapsulated inside zirconium (Zr)-based MOFs as the energy donor and green-emitting fluorescein isothiocyanate (FITC) as the energy acceptor. Especially, vancomycin (VAN) is employed as the recognition moiety to bind to the cell wall of S. aureus, leading to the disassembly of VAN-PEG-FITC from MOF HCAA@UiO-66. As the distance between the donor and acceptor increases, the donor signal correspondingly increases as the FRET signal decreases. By calculating the fluorescence intensity ratio, S. aureus can be quantified with a dynamic range of 1.05 × 103-1.05 × 107 CFU mL-1 and a detection limit of 12 CFU mL-1. Due to the unique high affinity of VAN to S. aureus, the nanoprobe shows high selectivity and sensitivity to S. aureus, even in real samples like lake water, orange juice, and saliva. The FRET-based ratiometric fluorescence bacterial detection method demonstrated in this work has a prospect in portable application and may reduce the potential threat of pathogens to human health.

Pyroptosis-Mediated Synergistic Photodynamic and Photothermal Immunotherapy Enabled by a Tumor-Membrane-Targeted Photosensitive Dimer

Overcoming the resistance to apoptosis and immunosuppression of tumor cells is a significant challenge in augmenting the effect of cancer immunotherapy. Pyroptosis, a lytic programmed cell-death pathway unlike apoptosis, is considered a type of immunogenic cell death (ICD) that can intensify the ICD process in tumor cells, releasing dramatically increased tumor-associated antigens and damage-associated molecular patterns to promote cancer immunotherapy. Herein, a tumor cell membrane-targeted aggregation-induced emission photosensitive dimer is found to be able to achieve highly efficient ICD under the synergistic effect of photodynamic and photothermal therapy. The photosensitive dimer can efficiently produce type-I reactive oxygen species (ROS) by photodynamic therapy in hypoxic tumor tissue, leading to pyroptosis by direct cell membrane damage, which is further reinforced by its photothermal effect. Furthermore, the enhanced ICD effect based on the dimer can completely eliminate the primary tumor on the seventh day of treatment and can also boost systemic antitumor immunity by generating immune memory, which is demonstrated by the superior antitumor therapeutic effects on both solid tumors and metastatic tumors when healing 4T1 tumor mouse models with poor immunogenicity.

Non-Covalent Dimer as Donor Chromophore for Constructing Artificial Light-Harvesting System in Water

Dynamic emissive materials in aqueous media have received much attention owing to their ease of preparation, tunable luminescence and environmental friendliness. However, hydrophobic fluorophores usually suffer from aggregation-caused quenching in water. In this work, we constructed an artificial light-harvesting system by using a non-covalent aggregation-induced emission dimer as antenna and energy donor. The dimer is quadruple hydrogen bonded from a ureidopyrimidinone derivative (M) containing a tetraphenylethylene group. The dispersed nano-assemblies based on the dimer in aqueous media were fabricated with the help of surfactant. By loading a hydrophobic acceptor molecule DBT into the nano-assemblies, man-made light-harvesting nanoparticles were fabricated, showing considerable energy transfer efficiency and a relatively high antenna effect. Additionally, the fluorescence color of the system can be gradually tuned by varying the content of the acceptors. This study provides a general way for the construction of an aqueous light-harvesting system based on a supramolecular dimer, which is important for potential application in luminescent materials.