Color-Tunable Amphiphilic Segmented π-Conjugated Polymer Nano-Assemblies and Their Bioimaging in Cancer Cells

Controlled assembly of photosensitizers through directional interactions for effective photooxidation

Despite the fact that effective photosensitizers (PSs) can be achieved through rational molecular design, controlling the hierarchical assemblies of individual PSs with distinct function and morphological nanoscopic architectures remains a challenge. Here, very ordered one-dimensional PS polymers and their hollow tubular structures are presented from aqueous assembly of organic PS-based di- or tri-blocked supramolecules. Di-blocked PSs were interdigitated into 1D fibrils, significantly quenching photooxidation. Meanwhile, tri-blocked PSs were tilted with respect to each other to generate hollow tubules, showing remarkable photo-activities as well as photo-stability, which are particularly suited for green chemistry due to their unusual rapid photo-oxidation.

Transition-Metal Free C-C Bond Cross-Coupling of Aryl Ethers with Diarylmethanes

We describe a general and efficient transition-metal free C-C bond cross-coupling of (hetero)aryl ethers and diarylmethanes via C(sp²)-O bond cleavage. The coupling reactions mediated by KHMDS proceeded well with high efficiency, broad substrate scope, and good functional group tolerance. The robustness and practicability of this protocol also have been demonstrated by easy gram-scale preparation and diversified product derivatization.

Supramolecular self-assembly mediated aggregation-induced emission of fluorene-derived cyanostilbenes: multifunctional probes for live cell-imaging

The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a positive role in enhancing the light-emission efficiency, has piqued the interest of many researchers as it opens up a new avenue for the exploration of practically beneficial luminescent materials. Diverse AIE-active luminogens (or AIEgens) with tunable emission colours and very high quantum yields (up to unity) in the solid state have been extensively utilised in a broad range of fields including optoelectronics, energy and bioscience. In this article, we describe novel fluorene-based fluorogens that exhibit bright emission in the solid-state, mechanical stimuli-responsive optical properties and aggregation-induced emissive ability, and were able to modulate their donor and acceptor properties. The target compounds were synthesized by a Knoevenagel condensation followed by Suzuki cross-coupling reaction, which tends to result in good yields. The target cyanostilbenes (4a-4d) show different reversibly switched states with high contrast through morphology modulation and demonstrate solvatochromic, vapochromic, and AIE properties. These results strongly suggest that compound 4d has better properties than the other derivatives (4a-c) due to the presence of extended donor-acceptor ability. Moreover, density-functional theory (DFT) calculations strongly support the UV-Vis and fluorescence spectral studies. The formation of nano-flakes and cuboid-shaped nanocrystals was further confirmed by FE-SEM and AFM studies. The synthesized compound 4d displayed very bright emission in the solid state and in the aggregate state as compared with the other derivatives (4a-4c). These results might be due to the presence of high-color contrast, which is an advantage for elucidation and overcomes the challenges exhibited in live-cell imaging applications. Moreover, an MTT assay on live A549 cells incubated with the target compound (4d) showed very low cytotoxicity even at high concentrations.

Programmed Macromolecular Assembly by Dipole-Dipole Interactions with Aggregation-Induced Enhanced Emission in Aqueous Medium

Self-assembling polymers by bioinspired directional supramolecular interactions currently hold great scientific and technological interests. Herein, we report an unorthodox strategy based on a dipole-dipole interaction-mediated extended antiparallel dipolar assembly of a model merocyanine (MC) dye for maneuvering the self-assembly of a highly water-soluble MC-functionalized block copolymer (P2). Unlike traditional amphiphilic block copolymers featuring distinct hydrophobic segments (flexible aliphatic hydrocarbon chains or rigid nonpolar aromatic scaffolds), P2 comprises polyethylene glycol monomethyl ether (PEG) as a hydrophilic block and an unconventional structure-directing acrylate block functionalized with polar MC-dyes in the side chains of every repeat unit. In the absence of any additional hydrophobic assistance, P2 spontaneously self-assembles in water through the continuous opposite alignment of its pendant MCs by multiple dipole-dipole interactions to cancel out their ground state dipole moments, which initially generates an H-aggregated species with ill-defined morphology (Aggregate 1). Upon thermal annealing, Aggregate 1 reorganizes into higher-order core-shell nanodisc-like structures (Aggregate 2) driven by the orthogonal π-stacking interactions of the rigid aromatic framework derived from the extended cofacial MC-stacks. The aromatic interiors of the nanodiscs gain colloidal stability from the externally decorated hydrophilic PEG chains. While the initially formed Aggregate 1, predominantly by dipole-dipole interactions, showed remarkable thermal stability due to the cooperative effect of the polymer chain, the hierarchical assembly guided by relatively weaker dispersion forces of the MC-stacked π-surfaces could be tailored by dilution or thermal treatment. Such organized packing of pendant MCs by the dual effect of dipole-dipole interactions and π-stacking conferred several exciting properties to the P2 assembly in water. Long-range ordered antiparallel stacking of the pendant MCs rendered outstanding aggregation-induced enhanced emission (AIEE) properties to the resultant nanostructures in water with increased fluorescence lifetime, quantum yield, and Stokes shift compared to nonaggregating P2 in CHCl₃. The remarkable thermal and kinetic stability of the nanodiscs, their guest loading ability, and very low critical aggregation concentration (CAC) were demonstrated by Förster resonance energy transfer (FRET) studies with an encapsulated donor-acceptor dye pair.

Hierarchical supramolecular co-assembly formation employing multi-component light-harvesting charge transfer interactions giving rise to long-wavelength emitting luminescent microspheres

Charge transfer (CT) interaction induced formation of a hierarchical supramolecular assembly has attracted attention due to its wide diversity of structural and functional characteristics. In the present work, we report the generation of green luminescent microspheres from the charge transfer interaction induced co-assembly of a bis-naphthyl dipicolinic amide (DPA) derivative with tetracyanobenzene (TCNB) for the first time. The properties of these self-assemblies were studied both in solution and the solid-state using spectroscopic and a variety of microscopy techniques. The X-ray crystal structure analysis showed a mixed stack arrangement of DPA and TCNB. The molecular orbital and energy level calculations confirm the charge transfer complex formation between DPA and TCNB. Furthermore, energy transfer was observed from the green luminescent CT complex to a red-emitting dye, pyronin Y, in the microsphere matrix, leading to the formation of a light-harvesting tri-component self-assembly.

Green luminescent microspheres, generated via charge-transfer interaction-induced hierarchical co-assembly of a bis-naphthyl dipicolinic amide derivative and tetracyanobenzene, transfer energy to long-wave emitting dye.

Cationic Polythiophene-based Colorimetric Assay for Probing the Activity of Protein Kinase A

In this work, a novel colorimetric assay based on polythiophene derivative (PMNT) was designed for the detection of protein kinase A (PKA). PKA can catalyze the phosphorylation of peptide, leading to the conformation change of PMNT from random-coil to planar, with the disappearance of absorption peaks above 500 nm and a color change from pink to yellow. The fabricated assay exhibits a wide linear range of 0.05 - 20 U/mL with a detection limit of 0.02 U/mL for PKA activity detection. The proposed protocol has promising prospects for use in clinical diagnosis related to PKA activity.

Stimuli-Responsive Supramolecular Chirality Switching and Nanoassembly Constructed by n-Shaped Amphiphilic Molecules in Aqueous Solution

Self-assembled nanomaterials composed of amphiphilic oligomers with functional groups have been applied in the fields of biomimetic chemistry and on-demand delivery systems. Herein, we report the assembly behavior and unique properties of an emergent n-shaped rod-coil molecule containing an azobenzene (AZO) group upon application of an external stimulus (thermal, UV light). The n-shaped amphiphilic molecules comprising an aromatic segment based on anthracene, phenyl linked with azobenzene groups, and hydrophilic oligoether (chiral) segments self-assemble into large strip-like sheets and perforated-nanocage fragments in an aqueous environment, depending on the flexible oligoether chains. Interestingly, the nano-objects formed in aqueous solution undergo a morphological transition from sheets and nanocages to small one-dimensional nanofibers. These molecules exhibit reversible photo- and thermal-responsiveness, accompanied by a change in the supramolecular chirality caused by the conformational transitions of the rod backbone. The architecture of n-shaped amphiphilic molecules with a photosensitive group makes them ideal candidates for intelligent materials for applications in advanced materials science.

Synthesis and self-seeding behavior of oligo(p-phenylene vinylene)-b-poly(N-(2-hydroxypropyl)methacrylamide)

This article reports the preparation of uniform fiber- and ribbon-like nanostructures via the self-seeding of OPV₅-b-PHPMA diblock copolymers.

Nucleophilic Amination and Etherification of Aryl Alkyl Thioethers

A transition-metal-free protocol capable of synthesizing diarylated aniline derivatives is reported. This method could be further employed to prepare aryl alkyl ethers. A wide range of thioethers, anilines, as well as alcohols were tolerated thanks to the mild reaction conditions. The strength of our method was demonstrated by performing a gram-scale reaction (20 mmol) followed by conversion of the nitrile group into synthetically useful aldehyde, ketone, and carboxylic acid.

New fluorescent through-space conjugated polymers: synthesis, optical properties and explosive detection

New through-space conjugated polymers based on a tetraphenylethene foldamer are explored and utilized in explosive detection in aqueous media.

Self-assembly of all-conjugated block copolymer nanoparticles with tailoring size and fluorescence for live cell imaging

Here, we describe aqueous nanoassemblies of rod–rod diblock polythiophene into core–shell nanospheres. Benefitting from their good photostability and low cytotoxicity, the nanoparticles meet the crucial requirements for cellular imaging and other biological applications.