Decheng Bai

A new rhodamine-based chemosensor for Cu2+ and the study of its behaviour in living cells.

A new rhodamine-based chemosensor (L1) was synthesized, and it exhibits high sensitivity and selectivity for the copper cation over other commonly coexistent metal ions in aqueous solution. Upon the addition of Cu(2+), the spirolactam ring of L1 was opened and a 1 : 1 metal-ligand complex was formed. Fluorescent imaging of Cu(2+) in living cells is also successfully demonstrated.

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.

A rhodamine-based “turn-on” fluorescent chemodosimeter for Cu2+ and its application in living cell imaging

A new fluorescent probe 1, N-(Rhodamine-6G)lactam-hydrazinecarbothioamide, was synthesized as a fluorescent and colorimetric chemodosimeter in aqueous solution for Cu(2+). Following Cu(2+)-promoted ring opening, redox and hydrolysis reactions, comparable amplifications of absorption and fluorescence signals were observed upon addition of Cu(2+); this suggests that chemodosimeter 1 effectively avoided the fluorescence quenching caused by the paramagnetic nature of Cu(2+). Importantly, 1 can selectively recognize Cu(2+) in aqueous media in the presence of other trace metal ions in organisms, abundant cellular cations and the prevalent toxic metal ions in the environment with high sensitivity (detection limit <3 ppb) and a rapid response time (<2 min). In addition, the biological imaging study has demonstrated that 1 can detect Cu(2+) in the living cells.

A coumarin-based two-photon probe for hydrogen peroxide.

A new fluorescence probe was developed for hydrogen peroxide (H2O2) detection based on donor-excited photo induced electron transfer (D-PET) mechanism, together with the benzil as a quenching and recognizing moiety. The benzil could convert to benzoic anhydride via a Baeyer-Villiger type reaction in the presence of H2O2, followed by hydrolysis of benzoicanhydride to give benzoic acid, and the fluorophore released. The probe was synthesized by a 6-step procedure starting from 4-(diethylamino)salicylaldehyde. A density functional theory (DFT) calculation was performed to demonstrate that the benzil was a fluorescence quencher. The probe was evaluated in both one-photon and two-photon mode, and it exhibited high selectivity toward H2O2 over other reactive oxygen species and high sensitivity with a detection limit of 0.09 μM. Furthermore, the probe was successfully applied to cell imaging of intracellular H2O2 levels with one-photon microscopy and two-photon microscopy. The superior properties of the probe made it of great potential use in more chemical and biological researches.

Transition metal complexes of 2, 6-di ((phenazonyl-4-imino) methyl)-4-methylphenol: structure and biological evaluation.

A symmetric ligand 2, 6-di ((phenazonyl-4-imino)methyl)-4-methylphenol (Dpmp) and its cobalt dinuclear complex (Co2(Dpmp)2(NO3)2(H2O)2·NO3·EtOH, (1) and zinc mononuclear complex Zn(Dpmp)(NO3)2, (2) have been prepared. The crystal structures were determined by single-crystal X-ray diffraction. The biological activity has been evaluated by examining their anti-oxidative activity and ability to bind to bovine serum albumin (BSA) and calf-thymus DNA (CT DNA) with UV-vis absorption, fluorescence, viscosity measurements and circular dichroism (CD) spectroscopies. The complexes exhibit good binding propensity to BSA and CT DNA. Both 1 and 2 have been found to promote cleavage of pUC19 DNA in the absence of any reducing agent. Antioxidant tests in vitro show the compounds possess significant antioxidant activity against superoxide and hydroxyl radicals.

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.