Junchen Wu

Amphiphilic diarylethene as a photoswitchable probe for imaging living cells.

This communication reports a unique example of water-soluble and fluorescent-switchable amphiphilic diarylethene. This compound performs stable vesicle aggregation in water and shows aggregation-dependent emission in its open form. The fluorescence can be effectively switched by alternating between UV and visible light irradiation. This compound thus can stain KB cells for switchable living cell imaging with excellent resistance to fatigue.

Peptide Functionalized Polydiacetylene Liposomes Act as a Fluorescent Turn-On Sensor for Bacterial Lipopolysaccharide

Mixed polydiacetylene (PDA) liposomes functionalized on their surface with a fluorescent pentalysine peptide derivative and histidine in a ratio of 1:9 can identify bacterial lipopolysaccharide (LPS). Upon photopolymerization of the self-assembled liposomes the initial fluorescence of the peptide-diacetylene amphiphiles is quenched. Interaction with LPS in aqueous solution or on the surface of E. coli DH5α restores the fluorescence. This increase in fluorescence is selective for LPS relative to other negatively charged analytes including nucleotides and ctDNA. This simple turn-on fluorescent sensor allows detecting LPS even at low micromolar concentrations.

Sonication-Triggered Instantaneous Gel-to-Gel Transformation

Two new peptide-based isomers containing cholesterol and naphthalic groups have been designed and synthesized. We found that the position of L-alanine in the linker could tune the gelation properties and morphologies. The molecule with the L-alanine residue positioned in the middle of the linker (1b) shows better gelation behavior than that with L-alanine directly linked to the naphthalimido moiety (1a). As a result, a highly thermostable organogel of 1b with a unique core-shell structure was obtained at high temperature and pressure in acetonitrile. Moreover, the gels of 1a and 1b could undergo an instantaneous gel-to-gel transition triggered by sonication. Ultrasound could break the core-shell microsphere of 1b and the micelle structure of 1a into entangled fibers. By studying the mechanism of the sonication-triggered gel-to-gel transition process of these compounds, it can be concluded that ultrasound has a variety of effects on the morphology, such as cutting, knitting, unfolding, homogenizing, and even cross-linking. Typically, ultrasound can cleave and homogenize pi-stacking and hydrophobic interactions among the gel molecules and then reshape the morphologies to form a new gel. This mechanism of morphology transformation triggered by sonication might be attractive in the field of material storage and controlled release.

Multiresponsive Switchable Diarylethene and Its Application in Bioimaging

A multiresponsive fluorescent switch based on diarylethene and terpyridine units was developed. It exhibits effective switchable fluorescence which can be controlled by UV/visible light or metal ion/EDTA in solution. More importantly, having low toxicity, it can enter live cells as a fluorescent probe and can also serve as a detector for the biological process of metal ion transmembrane transport.

A molecular peptide beacon for the ratiometric sensing of nucleic acids.

A pyrene-functionalized cationic oligopeptide 1 efficiently binds to double-stranded DNA, as shown by different spectrophotochemical studies. Upon binding, the conformation of 1 changes from a folded to an extended form, which leads to a distinct change in the fluorescence properties. Thus, 1 functions as a molecular peptide beacon, and as it is easily taken up by cells, 1 can also be used for imaging of nucleic acids within cells.

Tunable Gel Formation by Both Sonication and Thermal Processing in a Cholesterol-Based Self-Assembly System

A family of asymmetric cholesterol-based fluorescent organogelators containing naphthalimide, connected by two acylamines and different alkyl-chain spacers, have been designed and prepared. These compounds can gelate a variety of organic solvents with both ultrasound stimuli and general sol-gel processes. The self-assembly and gelling properties of the compounds depend on the length of the alkyl chains and can be controlled by ultrasound stimuli and renewed by a thermodynamic process. The morphologies and surface wetabilities of the xerogels prepared from these gelators are strongly affected by environmental stimuli. The mechanism of the process was investigated by confocal laser scanning microscopy, transmission or scanning electron microscopy, wide-angle X-ray scattering analysis, and rheological experiments. The studies reveal that the cooperation and relative competition of multiple intermolecular interactions, influenced by the sonication or thermal stimulus, are the main contributors for the aggregation or nucleation processes; this results in the macrodifferences in morphology and surface properties. These results provide a deeper understanding of the intermediate transition state of the gel during use of an ultrasound stimulus.

Tunable red–green–blue fluorescent organogels on the basis of intermolecular energy transfer

One or two-component gels with tunable emission colours were obtained from the assembly of three red–green–blue fluorescent molecules. The intermolecular energy transfer between these molecules played a crucial role in providing the tunable colour by a single excitation wavelength of 365 nm in the mixed gels. These gels are ideal constituents for the design of supramolecular light harvesting assembled materials, which afford a novel approach to display in soft organic materials with tunable optical properties.

Inclusion of tetracycline hydrochloride within supramolecular gels and its controlled release to bovine serum albumin.

Three amphiphilic 3,4,5-trihydroxybenzoic derivatives with alkyl chains of different lengths were designed and synthesized. A small amount of these compounds can trap a large quantity of the water-soluble drug tetracycline hydrochloride (TH) within a stable gel in aqueous ethanol. Release experiments were carried out with solutions of bovine serum albumin (BSA) and various concentrations of L-isoleucine, L-phenylalanine, and L-tryptophan. The results indicate that the release rate of TH for a BSA solution (10 mg/mL) was faster than that with the other solutions because of the strong interaction between TH and BSA. Furthermore, to gain an insight into the release dynamics, we studied the release ratios as a function of the square root of time (t1/2). During the initial 1.75 h, diffusion is the dominant release process in water, whereas intermolecular interaction controls TH release in the BSA solution.

Gelation induced reversible syneresis via structural evolution

This paper reports a large volume change in a cholesterol based molecular gel in the presence of multi-amine as the gelling solvents dissociated from the gel in a dynamic manner. The release capability can be controlled by the ratio of multi-amine. The shrinkage capability can be restored and recycled by a gel–sol transformation. The mechanism of the shrinkage was followed by SEM, confocal laser scanning microscopy and X-ray diffraction studies. A structural evolution from lamellar vesicles to a more compact hexagonal structure driven by competitive intermolecular hydrogen bonds was proved to dominate the process of the solvent release. Moreover, the process can be stopped by addition of organic acid such as trifluoroacetic acid, which favors the application of this kind of material for molecular delivery systems.

Molecular Beacons of Xeno-Nucleic Acid for Detecting Nucleic Acid

Molecular beacons (MBs) of DNA and RNA have aroused increasing interest because they allow a continuous readout, excellent spatial and temporal resolution to observe in real time. This kind of dual-labeled oligonucleotide probes can differentiate between bound and unbound DNA/RNA in homogenous hybridization with a high signal-to-background ratio in living cells. This review briefly summarizes the different unnatural sugar backbones of oligonucleotides combined with fluorophores that have been employed to sense DNA/RNA. With different probes, we epitomize the fundamental understanding of driving forces and these recognition processes. Moreover, we will introduce a few novel and attractive emerging applications and discuss their advantages and disadvantages. We also highlight several perspective probes in the application of cancer therapeutics.