Multiphase Behavior of Tetraphenylethylene Derivatives with Different Polarities at High Pressures

Polypseudorotaxanes Derived from Tetraphenylethylene: Preparation and Tandem-Activated Aggregation-Induced Emission

Tuning the fluorescence of aggregation-induced emission (AIE)-based materials in a reversible way is essential and a requisite for their applications. The multiple host-guest interactions of polypseudorotaxanes (PPRs) could alter the aggregation state of hydrophobic AIE-based polymeric materials and consequently switch the fluorescence. Herein, tetraphenylethylene (TPE) as a typical AIE molecule has been incorporated into the main chains of the guest polyurethane via a step condensation between poly(ethylene glycol) (PEG)-based dicarbonate and TPE-diamine along with the cleavable disulfide bonds. γ-Cyclodextrins (γ-CDs) can selectively recognize the TPE units at the polyurethane chains to afford a PPR. Hydrophilic PEG segments and γ-CD molecules in the PPR could promote the disaggregation of TPE units, suppressing the fluorescence emission of TPE. To restore the aggregated state and fluorescence of TPE units, tris(2-carboxyethyl)phosphine (TCEP) and α-amylase are sequentially introduced to cleave the disulfide bonds and cut α-1,4 glycosidic bonds of γ-CD, reactivating the AIE behavior of PPR tandemly and accomplishing the reversible cycle of tuning the fluorescence of TPE. The present study provides a tandem way to switch the AIE behavior of polymeric materials reversibly.

Ground- and excited-state dynamic control of an anion receptor by hydrostatic pressure

Stimulus-responsive supramolecular architectures have become an attractive alternative to conventional ones for many applications in sensing, drug-delivery and switchable memory systems. Herein, we used an anion receptor (H: host) as a hydrostatic-pressure-manipulatable fluorescence foldamer and halide anions as chiral (binaphthylammonium) and achiral (tetrabutylammonium) ion pairs (SS or RR ·X and TBA·X; X = Cl, Br), and then investigated their (chir)optical properties and molecular recognition behavior under hydrostatic pressures. The conformational changes and optical properties of H in various organic solvents were revealed by UV/vis absorption and fluorescence spectra and fluorescence lifetimes upon hydrostatic pressurization. The anion-recognition abilities of H upon interactions with SS or RR·X and TBA·X at different pressure ranges were determined by hydrostatic-pressure spectroscopy to quantitatively afford the binding constant (K anion) and apparent reaction volume changes . The results obtained indicate that hydrostatic pressure as well as solvation plays significant roles in the dynamic control of the present supramolecular system in the ground and excited states. This work will provide a new guideline for further developing hydrostatic-pressure-responsive foldamers and supramolecular materials.

Hydrostatic Pressure-Regulated Cellular Calcium Responses

Hydrostatic pressure control has attracted much attention and presents a still challenging objective from mechanobiological viewpoints. Herein, we reveal the calcium entry processes in HeLa cells by means of hydrostatic pressure spectroscopy. The steady-state fluorescence spectral data comprehensively elucidated the factors controlling the outcomes of the hydrostatic pressure-stimulated calcium entry behavior. The present work leads to a new perspective on ion regulations in living cells and an attractive alternative to conventional mechanostimuli.