Ni-Catalyzed Dimerization and Arylation of Diarylacetylenes with Arylboronic Acids

A new, facile, and efficient protocol for the synthesis of polysubstituted conjugated 1,3-dienes through Ni-catalyzed tandem dimerization/cross-coupling reaction of diarylacetylenes and arylboronic acids in the presence of a catalytic amount of B₂pin₂ has been developed. A series of arynes and arylboronic acids with different substituents participated well in this catalytic system, affording a variety of useful conjugated 1,3-dienes

Palladium-Catalyzed Hydrocarbonylative C–N Coupling of Alkenes with Amides

An efficient palladium-catalyzed hydrocarbonylative C–N coupling of alkenes with amides has been developed. The reaction was performed via hydrocarbonylation of alkenes, followed by acyl metathesis with amides. Both intermolecular and intramolecular reactions proceed smoothly to give either branched or linear amides in high turnover number (3500) with NH₄Cl or NMP·HCl as a proton source under the palladium catalysis. This reaction offers a catalytic convenient approach to deuterated amides when inexpensive NMP·DCl served as a deuterium source

Highly Selective Fluorogenic Multianalyte Biosensors Constructed via Enzyme-Catalyzed Coupling and Aggregation-Induced Emission

The development of a highly selective and fast responsive fluorogenic biosensor for diverse analytes ranging from bioactive small molecules to specific antigens is highly desirable but remains a considerable challenge. We herein propose a new approach by integrating substrate-selective enzymatic reactions with fluorogens exhibiting aggregation-induced emission feature. Tyrosine-functionalized tetraphenylethene, TPE-Tyr, molecularly dissolves in aqueous media with negligible fluorescence emission; upon addition of horseradish peroxidase (HRP) and H₂O₂, effective cross-linking occurs due to HRP-catalyzed oxidative coupling of tyrosine moieties in TPE-Tyr. This leads to fluorescence emission turn-on and fast detection of H₂O₂ with high sensitivity and selectivity. As a validation of the new strategy’s generality, we further configure it into the biosensor design for glucose through cascade enzymatic reactions and for pathologically relevant antigens (e.g., human carcinoembryonic antigen) by combining with the ELISA kit

Efficient Synthesis of Single Gold Nanoparticle Hybrid Amphiphilic Triblock Copolymers and Their Controlled Self-Assembly

We report on a robust approach to the size-selective and template-free synthesis of asymmetrically functionalized ultrasmall (<4 nm) gold nanoparticles (AuNPs) stably anchored with a single amphiphilic triblock copolymer chain per NP. Directed NP self-assembly in aqueous solution can be facilely accomplished to afford organic/inorganic hybrid micelles, vesicles, rods, and large compound micelles by taking advantage of the rich microphase separation behavior of the as-synthesized AuNP hybrid amphiphilic triblock copolymers, PEO–AuNP–PS, which act as the polymer–metal–polymer analogue of conventional amphiphilic triblock copolymers. Factors affecting the size-selective fabrication and self-assembly characteristics and the time-dependent morphological evolution of NP assemblies were thoroughly explored

Rationally Engineering Phototherapy Modules of Eosin-Conjugated Responsive Polymeric Nanocarriers via Intracellular Endocytic pH Gradients

Spatiotemporal switching of respective phototherapy modes at the cellular level with minimum side effects and high therapeutic efficacy is a major challenge for cancer phototherapy. Herein we demonstrate how to address this issue by employing photosensitizer-conjugated pH-responsive block copolymers in combination with intracellular endocytic pH gradients. At neutral pH corresponding to extracellular and cytosol milieu, the copolymers self-assemble into micelles with prominently quenched fluorescence emission and low ¹O₂ generation capability, favoring a highly efficient photothermal module. Under mildly acidic pH associated with endolysosomes, protonation-triggered micelle-to-unimer transition results in recovered emission and enhanced photodynamic ¹O₂ efficiency, which synergistically actuates release of encapsulated drugs, endosomal escape, and photochemical internalization processes

Rh-Catalyzed Sequential Oxidative C–H and N–N Bond Activation: Conversion of Azines into Isoquinolines with Air at Room Temperature

A rhodium-catalyzed sequential oxidative C–H annulation reaction between ketazines and internal alkynes has been developed via C–H and N–N bond activation with air as an external oxidant, which led to an efficient approach toward isoquinolines with high atom efficiency at rt. Utilizing the distinctive reactivity of this catalysis, both N-atoms of the azines could be efficiently incorporated to the desired isoquinolines under very robust and mild reaction conditions

Schizophrenic Core–Shell Microgels: Thermoregulated Core and Shell Swelling/Collapse by Combining UCST and LCST Phase Transitions

A variety of slightly cross-linked poly­(2-vinylpyridine)–poly­(<i>N</i>-isopropylacrylamide) (P2VP–PNIPAM) core–shell microgels with pH- and temperature-responsive characteristic were prepared via seeded emulsion polymerization. Negatively charged sodium 2,6-naphthalenedisulfonate (2,6-NDS) could be internalized into the inner core, followed by formation of (P2VPH⁺/SO₃^2–) supramolecular complex through the electrostatic attractive interaction in acid condition. The thermoresponsive characteristic feature of the (P2VPH⁺/SO₃^2–)–PNIPAM core–shell microgels was investigated by laser light scattering and UV–vis measurement, revealing an integration of upper critical solution temperature (UCST) and lower critical solution temperature (LCST) behaviors in the temperature range of 20–55 °C. The UCST performance arised from the compromised electrostatic attractive interaction between P2VPH⁺ and 2,6-NDS at elevated temperatures, while the subsequent LCST transition is correlated to the thermo-induced collapse of PNIPAM shells. The controlled release of 2,6-NDS was monitored by static fluorescence spectra as a function of temperature change. Moreover, stopped-flow equipped with a temperature-jump accessory was then employed to assess the dynamic process, suggesting a millisecond characteristic relaxation time of the 2,6-NDS diffusion process. Interestingly, the characteristic relaxation time is independent of the shell cross-link density, whereas it was significantly affected by shell thickness. We believe that these dual thermoresponsive core–shell microgels with thermotunable volume phase transition may augur promising applications in the fields of polymer science and materials, particularly for temperature-triggered release

An Efficient Rh/O₂ Catalytic System for Oxidative C–H Activation/Annulation: Evidence for Rh(I) to Rh(III) Oxidation by Molecular Oxygen

A novel and efficient Rh/O₂ catalytic system has been developed and shown to catalyze highly efficient oxidative C–H activation/annulation reactions, producing a broad range of isoquinolinium salts with high turnover numbers (up to 740). Mechanistic studies provided strong evidence of facile oxidation of Rh­(I) to Rh­(III) by molecular oxygen facilitated by acid

Self-Immolative Polymersomes for High-Efficiency Triggered Release and Programmed Enzymatic Reactions

Stimuli-triggered disassembly of block copolymer vesicles or polymersomes has been conventionally achieved via solubility switching of the bilayer-forming block, requiring cooperative changes of most of the repeating units. Herein we report an alternative approach by incorporating hydrophobic blocks exhibiting stimuli-triggered head-to-tail cascade depolymerization features. Amphiphilic block copolymers bearing this motif self-assemble into self-immolative polymersomes (SIPsomes). By modular design of terminal capping moieties, visible light, UV light, and reductive milieu can be utilized to actuate SIPsomes disintegration into water-soluble small molecules and hydrophilic blocks. The design of SIPsomes allows for triggered drug co-release and controllable access toward protons, oxygen, and enzymatic substrates. We also demonstrate programmed (OR-, AND-, and XOR-type logic) enzymatic reactions by integrating SIPsome encapsulation and trigger/capping moiety-selective cascade depolymerization events

Intracellular Cascade FRET for Temperature Imaging of Living Cells with Polymeric Ratiometric Fluorescent Thermometers

Intracellular temperature plays a prominent role in cellular functions and biochemical activities inside living cells, but effective intracellular temperature sensing and imaging is still in its infancy. Herein, thermoresponsive double hydrophilic block copolymers (DHBCs)-based fluorescent thermometers were fabricated to investigate their application in intracellular temperature imaging. Blue-emitting coumarin monomer, CMA, green-emitting 7-nitro-2,1,3-benzoxadiazole (NBD) monomer, NBDAE, and red-emitting rhodamine B monomer, RhBEA, were copolymerized separately with <i>N</i>-isopropylacrylamide (NIPAM) to afford dye-labeled PEG-<i>b</i>-P­(NIPAM-<i>co</i>-CMA), PEG-<i>b</i>-P­(NIPAM-<i>co</i>-NBDAE), and PEG-<i>b</i>-P­(NIPAM-<i>co</i>-RhBEA). Because of the favorable fluorescence resonance energy transfer (FRET) potentials between CMA and NBDAE, NBDAE and RhBEA, as well as the slight tendency between CMA and RhBEA fluorophore pairs, three polymeric thermometers based on traditional one-step FRET were fabricated by facile mixing two of these three fluorescent DHBCs, whereas exhibiting limited advantages. Thus, two-step cascade FRET among three polymeric fluorophores was further interrogated, in which NBD acted as a bridging dye by transferring energy from CMA to RhBEA. Through the delicate optimization of the molar contents of three polymeric components, a ∼8.4-fold ratio change occurred in the temperature range of 20–44 °C, and the detection sensitivity improved significantly, reached as low as ∼0.4 °C, which definitely outperformed other one-step FRET thermometers in the intracellular temperature imaging of living cells. To our knowledge, this work represents the first example of polymeric ratiometric thermometer employing thermoresponsive polymer-based cascade FRET mechanism