Ju Cheng

A sensitive colorimetric and ratiometric fluorescent probe for mercury species in aqueous solution and living cells

A highly sensitive and selective fluorescent probe for inorganic and organic mercury species displays colorimetric and ratiometric response in a buffer solution via mercury promoted cleavage reaction. The probe is demonstrated to detect CH(3)HgCl in living cells.

Biomimetic and Cell-Mediated Mineralization of Hydroxyapatite by Carrageenan Functionalized Graphene Oxide

In bone tissue engineering, it is imperative to design multifunctional biomaterials that can induce and assemble bonelike apatite that is close to natural bone. In this study, graphene oxide (GO) was functionalized by carrageenan. The resulting GO-carrageenan (GO-Car) composite was further used as a substrate for biomimetic and cell-mediated mineralization of hydroxyapatite (HA). It was confirmed that carrageenan on the GO surface facilitated the nucleation of HA. The observation of the effect of the GO-Car on the adhesion, morphology, and proliferation of MC3T3-E1 cells was investigated. In vitro studies clearly show the effectiveness of GO-Car in promoting HA mineralization and cell differentiation. The results of this study suggested that the GO-Car hybrid will be a promising material for bone regeneration and implantation.

Cu2+-selective fluorescent chemosensor based on coumarin and its application in bioimaging

A new fluorescent sensor L1 based on coumarin was synthesized. It shows high sensitivity and selectivity toward Cu(2+) in aqueous solution. The complexation mode and corresponding quenching mechanism were elucidated by ESI-MS and DFT calculations. In addition, biological imaging studies have demonstrated that L1 can detect Cu(2+) in living cells.

Gelatin functionalized graphene oxide for mineralization of hydroxyapatite: biomimetic and in vitro evaluation

We report a facile modification of graphene oxide (GO) by gelatin to mimic charged proteins present in the extracellular matrix during bone formation. The bioinspired surface of GO-gelatin (GO-Gel) composite was used for biomimetic mineralization of hydroxyapatite (HA). A detailed structural and morphological characterization of the mineralized composite was performed. Additionally, MC3T3-E1 cells were cultured on the GO-Gel surfaces to observe various cellular activities and HA mineralization. Higher cellular activities such as cell adhesion, cell proliferation, and alkaline phosphatase activity (ALP) were observed on the GO-Gel surface compared with the GO or glass surface. The increase of ALP confirms that the proposed GO-Gel promotes the osteogenic differentiation of MC3T3-E1 cells. Moreover, the evidence of mineralization evaluated by scanning electron microscopy (SEM) and alizarin red staining (ARS) corroborate the idea that a native osteoid matrix is ultimately deposited. All these data suggest that the GO-Gel hybrids will have great potential as osteogenesis promoting scaffolds for successful application in bone surgery.

Fluorescent graphene oxide composites synthesis and its biocompatibility study

In this research, we developed a “clean” and “wet” route to produce sandwich-like fluorescent CdQ2/GO composites sheets starting from graphene oxide (GO) and Cd2+ in water/ethanol solution in one pot. The as-prepared CdQ2/GO composites sheets were fully characterized by IR, XRD, TEM and TGA analysis. The CdQ2/GO composites exhibited a strong fluorescence emission centered at 500 nm. Both the solid sample and the water dispersion could demonstrate strong green fluorescence. When incubated with Hep G2 cells at 37 °C, the CdQ2/GO composites were found to adhere to the surroundings of the cell membrane, resulting in strong green fluorescence observed by laser confocal fluorescence microscopy. MTT assay experiment results showed that this kind of composite material had low cytotoxicity at the concentration of 400 μg mL−1. We believe this method and composite materials will open up a brand new avenue for wider applications of graphene-based materials in the detection of other types of biomarkers, biomolecular interactions, and fluorescence imaging in vitro and in vivo.

An 1,3,4-oxadiazole-based OFF–ON fluorescent chemosensor for Zn2+ in aqueous solution and imaging application in living cells

A new 1,3,4-oxadiazole-based fluorescence chemosensor 1, N-(2-ethoxy-2-oxoethyl)-N-(5-(2-hydroxy-3,5-di-tert-butylphenyl)-[1,3,4]oxadiazol-2-yl)glycine ethyl ester, has been designed and synthesized. Its fluorescence properties and selectivity for various metal ions were investigated in detail. A prominent fluorescence enhancement only for Zn(2+) was found in aqueous acetonitrile solution and the response mechanism of 1 was analyzed by time-resolved fluorescence decay and DFT calculations. Furthermore, the fluorescence imaging of Zn(2+) in living cells was successfully applied.

A sensitive colorimetric and ratiometric fluorescent chemodosimeter for Hg2+ and its application for bioimaging

A colorimetric and ratiometric fluorescent chemodosimeter for Hg2+ has been developed based on mercury ion-promoted hydrolysis of a naphthalimide-derived aryl vinyl ether. The chemodosimeter displays a highly sensitive and selective response with significant changes in both color (from colorless to jade-yellow) and fluorescence (from blue to green) in PBS buffer solution (containing 1% CH3CN, pH = 7.4). The chemodosimeter exhibits a ratiometric fluorescent response towards Hg2+ with a very low detection limit (3.6 nM), which can be used to detect Hg2+ ions in drinking water. Furthermore, the chemodosimeter has been successfully applied to the imaging of Hg2+ ions in living cells with an emission change from blue to green.

A coumarin-derived fluorescent chemosensor for selectively detecting Cu2+ : Synthesis, DFT calculations and cell imaging applications

A novel coumarin-based fluorescent probe L ((4E)-4-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl) methyleneamino)-1,2-dihyydro-2,3-dimethyl-1-phenylpyrazol-5-one) has been developed as a simple and efficient chemosensor which exhibits a significant fluorescence reduction in the presence of metal cations. This sensor exhibits high selectivity and sensitivity toward Cu(2+) over other common cations. The mechanism for detecting copper was evaluated by time-dependent density functional theory (TD-DFT) calculations and the coordination mode was also confirmed by density functional theory (DFT) calculations. Furthermore, results of cell imaging in this study indicate that this new probe may be useful for detection and monitoring of Cu(2+) in biological applications.

MC3T3-E1 preosteoblast cell-mediated mineralization of hydroxyapatite by poly-dopamine-functionalized graphene oxide

We report a biomimetic mineralization of hydroxyapatite induced by poly-dopamine-functionalized reduced graphene oxide (RGO-PDA). Graphene oxide was first simultaneously reduced and surface functionalized by one-step oxidative polymerization of dopamine. The resultant RGO-PDA was further used as a bioinspired surface to mimic the mineralization of hydroxyapatite during bone formation. MC3T3-E1 cells were cultured on the RGO-PDA substrates to observe various cellular activities and hydroxyapatite mineralization. The MC3T3-E1 cells on RGO-PDA substrates show higher cellular activities such as proliferation, adhesion, and osteogenic differentiation over the bare glass and graphene oxide substrates. Those results suggest the potentials of using RGO-PDA as osteogenesis-promoting scaffolds for successful applications in bone tissue regeneration.

New fluorescent probe for Zn2+ imaging in living cells and plants

A new fluorescent probe, L1 based on 8-aminoquinoline, was designed and synthesized. It exhibits high selectivity and sensitivity toward Zn2+ over other common metal ions (especially Cd2+). Under physiological conditions (pH 7.0), the probe displays an 8-fold fluorescence turn-on response to Zn2+. Furthermore, using laser scanning confocal techniques, it can be used to effectively monitor and distinguish Zn2+ from Cd2+ in living cells and plant tissues.