Shuangshuang Chen

Preparation of aggregation-induced emission dots for long-term two-photon cell imaging

Two-photon fluorescence imaging has attracted increasing interest in the biological and medical fields because of its low cell damage, high resolution, large imaging depth, and easy dynamic observation. A high-performance two-photon probe with long-term imaging capability was proposed for this imaging technology. In this work, a new two-photon probe compound was synthesized from tetraphenylethylene fluorogen with aggregation-induced emission. A phenyl-[phenyl-(1,2,5-thialdiazol)] amine group was induced to red-shift the absorption and emission wavelengths of the compound. After self-assembly, fluorescent dots with aggregation-induced emission cores and hydrophobic shells terminated by -COOH were formed. Cell experiments proved that the 4-(7-(phenyl(4-(1,2,2-triphenylvinyl)phenyl)amino)benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid (TPECOOH) dots with red emission showed good biocompatibility and excellent two-photon imaging ability. TPECOOH dots were used successfully in direct long-term cell imaging with high efficiency. Even after twelve days, fluorescence imaging could still be observed in live HeLa cells.

Injectable and cross-linkable polyphosphazene hydrogels for space-filling scaffolds

Low mechanical strength is a major disadvantage of injectable hydrogels. Although the mechanical properties of hydrogels can be improved by the introduction of robust materials, the use of conventional reinforcing agents limits the medical application of injectable hydrogels due to their non-biodegradable property. We synthesized and self-assembled an injectable hydrogel from biodegradable mixed-substituted polyphosphazene and the natural organic molecule α-cyclodextrin (αCD) by host–guest inclusion. Photo-crosslinking was then employed for the hydrogel to transform it into the solid state with the desired shape. By this approach, the mechanical properties and anti-water solubility of the polyphosphazene hydrogel can meet the requirements of potential applications. In addition, the surface of the cured hydrogel can be readily tuned from cell-philic to cell-phobic by changing the ratio of two side chains of substituted polyphosphazene.

Electrochemically Tunable Cell Adsorption on a Transparent and Adhesion-Switchable Superhydrophobic Polythiophene Film

A superhydrophobic polythiophene film (SSPTH) is prepared by double-layer electrodeposition on an indium tin oxide (ITO) glass electrode. This film shows not only electroresponsive superhydrophobic features, but also high transparency compared with the usual polythiophene film. The water-droplet adhesion on the SSPTH film can be switched between sliding and pinned states under the applied potential. More intresetingly, the change in water-droplet adhesion results in a change in cell adsorption on the SSPTH film. The low-adhesion (dedoped) SSPTH films can prevent Hela cell adhesion, whereas high-adhesion (doped) SSPTH films can promote Hela cell adsorption. This controllable cell adhesion on a SSPTH film may be developed as a smart biointerface material.

Formation and properties of liquid crystalline supramolecules with anisotropic fluorescence emission

Two kinds of liquid crystalline (LC) supramolecules with anisotropic fluorescence emission were prepared by ionic self-assembly from a copolymer, derived from acrylic acid and 6-(4′-cyanobiphenyl-4-yloxy)hexyl acrylate, and oppositely charged fluorescent molecules: stilbene-based rod-like dye (Stil) or tetraphenylethene-based propeller-like dye (TPE). The supramolecules exhibited a nematic LC nature and the different structure of the fluorescent units showed different effect on the LC behaviour of the supramolecules. After being spin-coated onto an oriented PVA film, the liquid crystalline supramolecule film was thermally annealed and the anisotropic fluorescence emission was investigated. A different thermal amplification effect was found depending on the different structure of the fluorescent unit. This conclusion provides a new perspective on the design of a high-performance fluorescence polarization film.

A strategy for the synthesis of cyclomatrix-polyphosphazene nanoparticles from non-aromatic monomers

Cyclomatrix-polyphosphazenes (C-PPZs) are a new class of nanomaterials that have attracted significant interest owing to their unique inorganic–organic hybrid structure and tunable properties. The limited success that has been achieved in producing C-PPZs from non-aromatic organic monomers is ascribed to an insufficient understanding of their polymerization mechanism. In this work, by using a new strategy termed solubility-parameter-triggered polycondensation, we demonstrate experimentally and computationally that C-PPZs nanoparticle synthesis from non-aromatic monomers is feasible and solubility-parameter (SP)-dependent. The precipitation polycondensation of C-PPZ occurs once the solution SP is outside a critical SP range, while within the critical range only oligomers are detected from the reaction; this SP-dependent rule is applicable for C-PPZ oligomers from both aromatic and non-aromatic monomers. The upper/lower critical SP values increase with the increase of organic monomer hydrophilicity. The morphologies of C-PPZ products exist as clusters or nanoparticles when the reaction solvent SP is controlled below the upper critical SP or exceeds the lower critical SP, respectively. This theory presents a feasible way to predict and determine the precipitation polycondensation conditions and product morphology of any novel C-PPZ nanomaterial.

Comparison of hybrid polyimide films with silica and organosilica obtained via sol–gel process:

A series of polyimide/silica (PI–S) and polyimide/organosilica (PI–OS) hybrid films were prepared via a sol–gel process from mixtures of poly(amic acid) (PAA) and tetraethoxysilane or a silane coupling agent in solution. The PAA was synthesized from bis-(3-phthalyl anhydride) ether and 1,4-bis (4-aminophenoxy) benzene. The hybrid films were produced via an imidization reaction to form silica particles or a silica network in a polymer matrix through a programmed heating process. The derived films were characterized and compared by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, tensile testing, contact angle measurements, moisture absorption measurements, and dielectric property analysis. Both the PI–S and PI–OS hybrid matrixes showed strong regularity with the increasing silica content and greatly improved thermal stability and mechanical properties. Among them, the PI–OS hybrid films possessed superior interphase interactions and were found to have better physicochemical properties.