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.

A coumarin-derived fluorescent chemosensor for selectively detecting Cu²âº: 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.

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.

Hybrid composite Ni(OH)2@NiCo2O4 grown on carbon fiber paper for high-performance supercapacitors.

We have successfully fabricated and tested the electrochemical performance of supercapacitor electrodes consisting of Ni(OH)2 nanosheets coated on NiCo2O4 nanosheets grown on carbon fiber paper (CFP) current collectors. When the NiCo2O4 nanosheets are replaced by Co3O4 nanosheets, however, the energy and power density as well as the rate capability of the electrodes are significantly reduced, most likely due to the lower conductivity of Co3O4 than that of NiCo2O4. The 3D hybrid composite Ni(OH)2/NiCo2O4/CFP electrodes demonstrate a high areal capacitance of 5.2 F/cm(2) at a cycling current density of 2 mA/cm(2), with a capacitance retention of 79% as the cycling current density was increased from 2 to 50 mA/cm(2). The remarkable performance of these hybrid composite electrodes implies that supercapacitors based on them have potential for many practical applications.

Facile synthesis of Pd-based bimetallic nanocrystals and their application as catalysts for methanol oxidation reaction.

We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations.

In situ preparation, characterization, magnetic and catalytic studies of surfactant free RGO/Fe(x)Co(100-x) nanocomposites.

A novel, "wet" and "clean" methodology was developed to prepare Fe(x)Co(100-x) nanoparticles on reduced graphene oxide (RGO) surfaces in an aqueous solution through a coreduction process. Without any surface treatment, Fe(x)Co(100-x) nanoparticles can in situ grow on the RGO sheets. It was found that RGO nanosheets can effectively prevent the aggregation of Fe(x)Co(100-x) nanoparticles. The results reveal that the RGO/Fe(x)Co(100-x) nanocomposites have ferromagnetic characteristics and show composition dependent magnetic properties. The effectiveness of the as-prepared RGO/Fe(x)Co(100-x) nanocomposites as solid phase heterogeneous catalysts have been evaluated, for the first time, on the well-known 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) in the presence of excess sodium borohydride. The effect of initial 4-NP concentration, and catalyst loading dose were evaluated. The catalyst efficiency was examined on the basis of turnover frequency (TOF) and recyclability. The RGO/Fe25Co75 nanocomposites exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the graphene oxide (GO) supports also enhance the catalytic activity via a synergistic effect. The as-prepared RGO/Fe(x)Co(100-x) nanocomposite catalysts are very efficient, stable, easy to prepare, eco-friendly, cost-effective, and have potential industrial applications.

Selective off-on fluorescent chemosensor for detection of Fe3+ ions in aqueous media.

A Fe(3+) chemosensor L1 was successfully synthesized with a quinoline moiety bound to rhodamine 6G hydrazide. The sensor L1 shows high selectivity and sensitivity to Fe(3+) in aqueous solution in the presence of other trace metal ions in organisms, abundant cellular cations and prevalent toxic metal ions in the environment. In addition, biological imaging and micro computed tomography (MCT) technology studies have demonstrated that L1 could act as a turn-on fluorescent chemosensor for Fe(3+) in living cells.

Surfactant free RGO/Pd nanocomposites as highly active heterogeneous catalysts for the hydrolytic dehydrogenation of ammonia borane for chemical hydrogen storage.

In this study, monodisperse palladium (Pd) nanoparticles on reduced graphene oxide (RGO) surfaces were successfully prepared by a "wet" and "clean" method in aqueous solution. Without any surface treatment, Pd nanoparticles are firmly attached to the RGO sheets. These RGO/Pd nanocomposites exhibited catalytic activity in hydrogen generation from the hydrolysis of ammonia borane (AB). Their hydrolysis completion time and activation energy were 12.5 min and 51 ± 1 kJ mol(-1), respectively, which were comparable to the best Pd-based catalyst reported. The TOF values (mol of H(2)× (mol of catalyst × min)(-1)) of RGO/Pd is 6.25, which appears to be one of the best catalysts reported so far. We also obtained a (11)B NMR spectrum to investigate the mechanism of this catalytic hydrolysis process. This simple and straightforward method is of significance for the facile preparation of metal nanocatalysts with high catalytic activity on proper supporting materials.

Recognition of copper and hydrogen sulfide in vitro using a fluorescein derivative indicator.

We report the development of a fluorescein-based chemosensor (L1) for monitoring ions or micromolecules (H(2)S). Copper ions are known to be toxic at high concentrations and hydrogen sulfide induces various problems. Herein we develop a simple method for detecting Cu(II) and H(2)S with high selectivity and sensitivity. The chemosensor L1 displays on-off-on type fluorescence change with alternately added Cu(II) and H(2)S to the media along with reversible forming-separating of the complex. The potential biomedical relevance of the chemical mechanisms involved in the detection of L1 is described.

K, Ca complexes with a sulfonic ligand: structure and DNA-binding properties.

A novel 4-(2,4-dihydroxybenzylideneamino)benzenesulfonic acid (HL), and its kalium(I), calcium(II) complexes [M(L)n]·2nH(2)O·Cl(n) (M=K(1) n=1, M=Ca(2) n=2), have been prepared and characterized. The crystal and molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The interaction of 1, 2 and ligand (L) with calf thymus DNA was investigated by UV-visible (UV-vis), fluorescence and viscosity measurements. Experimental results indicate that 1, 2 and L could bind to DNA via the intercalation mode, and the binding affinity of 1 is stronger than that of 2 and L. The intrinsic binding constants of 1, 2 and L were 5.60×10(5), 6.53×10(5) and 1.44×10(5)M(-1), respectively. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. The results indicated that 1 and 2 could cleave pBR322 DNA.

Magnetic Fe3O4 nanoparticles coupled with a fluorescent Eu complex for dual imaging applications.

Magnetic 8 nm Fe(3)O(4) nanoparticles (NPs) were synthesized and modified with dopamine (DPA) and polyethylene glycol (PEG) diacid. The water soluble Fe(3)O(4)-DPA-PEG NPs were then conjugated with the fluorescent Eu(iii) complex of tris(dibenzoylmethane)-5-amino-1,10-phenanthroline (BMAP), giving an Fe(3)O(4)-DPA-PEG-BMAP-Eu NP conjugate. The conjugate was both colloidally and chemically stable in phosphate buffered solutions and could be used as a probe for magnetic resonance and fluorescent imaging.

A retrievable and highly selective fluorescent probe for monitoring sulfide and imaging in living cells.

A novel selective fluorescent chemosensor based on an 8-hydroxyquinoline-appended fluorescein derivative (L1) was synthesized and characterized. Once combined with Cu(2+), it displayed high specificity for sulfide anion. Among the various anions, only sulfide anion induced the revival of fluoresecence of L1, which was quenched by Cu(2+), resulting in "off-on"-type sensing of sulfide anion. What's more, the sensor was retrievable to indicate sulfide anions with Cu(2+), and S(2-), in turn, increased. With the addition of Cu(2+), compound L1 could give rise to a visible pink-to-yellow color change and green fluorescence quenching. The resulting yellow solution could change to pink and regenerate to green fluorescence immediately upon the addition of sulfide anion; however, no changes were observed in the presence of other anions, including CN(-), P(2)O(7)(4-), and other forms of sulfate, making compound L1 an extremely selective and efficient sulfide chemosensor. The signal transduction occurs via reversible formation-separation of complex L1Cu and CuS. What's more, the biological imaging study has demonstrated that the chemosensor can detect sulfur anions in biological systems at a relatively low concentration.

Spectroscopic studies on the interaction between an anticancer drug ampelopsin and bovine serum albumin.

The interaction between bovine serum albumin (BSA) and the anticancer drug molecule ampelopsin (AMP) was investigated using fluorescence spectroscopy, circular dichroism (CD) spectra, and time-resolved spectra under simulated physiological conditions. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by AMP in terms of a dynamic quenching process. Binding constants and binding sites were calculated. The thermodynamic parameters indicated that the hydrogen bonding and weak van der Waals force played a major role in the interaction. The site marker competitive experiments suggested that the binding site of AMP and BSA was probably located on site III. Based on the Förster's theory, the average binding distance between AMP and BSA was obtained (r=5.47nm). The binding of AMP and BSA leaded to conformational changes of BSA according to synchronous fluorescence spectra, CD data and mean fluorescence lifetime values.

Cu(2+)-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.

Synthesis, DNA binding and cleavage activities of copper (II) thiocyanate complex with 4-(N,N-dimethylamino)pyridine and N,N-dimethylformamide.

Two novel copper(II) thiocyanate complexes with 4-(N,N-dimethylamino) pyridine and N,N-dimethylformamide (1) and with 4-(N,N-dimethylamino) pyridine (2) have been synthesized and characterized. The crystal and molecular structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Antioxidative activity tests in vitro showed that complex 1 has significant antioxidative activity against hydroxyl free radicals from the Fenton reaction and also oxygen free radicals, which is better than standard antioxidants like vitamin C and mannitol. The interaction of complex 1 with calf thymus DNA was investigated by spectroscopic, cyclic voltammetry, and viscosity measurements. Results suggest that complex 1 can bind to DNA via partial intercalation mode. Moreover, complex 1 has been found to cleavage of plasmid DNA pBR322.

Biocompatible hydroxyapatite nanoparticles as a redox luminescence switch.

A redox luminescence switch was prepared by doping hydroxyapatite nanoparticles with CePO(4):Tb. The resulting multifunctional material exhibits good biocompatibility, biological affinity, and potential drug-carrying capability. The luminescent hydroxyapatite nanoparticles may find important applications in biomedical diagnostics, drug delivery, and biological sensors.

A turn-on chemosensor for Hg2+ in aqueous media and its application in "MCT" imaging in living cells.

A turn-on chemosensor L1, which exhibits high selectivity and sensitivity toward Hg(2+) over other common metal ions in aqueous media under a physiological pH window via a 1:1 binding mode, had been synthesized and characterized. L1 provides good fluorescent imaging of Hg(2+) in living cells. Particularly, we adopted the "micro computed tomography (MCT)" technology, successfully demonstrating the method of Hg(2+) sensing by L1 in cell lines, also the cell permeability of L1 and its imaging position in the cells.

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.

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.

Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA.

The binding properties on [PrL2(NO3)](NO3)2 (L=9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7Hpyrido[1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) to bovine serum albumin (BSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-Vis absorbance spectroscopy. The results showed that [PrL2(NO3)](NO3)2 strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was about 1, and the efficiency of Förster energy transfer provided a distance of 4.26 nm between tryptophan and [PrL2(NO3)](NO3)2 binding site. At 288, 298, 310 K, the quenching constants of BSA-[PrL2(NO3)](NO3)2 system were 5.11×10(4), 4.33×10(4) and 3.71×10(4) l M(-1). ΔH, ΔS and ΔG were obtained based on the quenching constants and thermodynamic theory (ΔH<0, ΔS>0 and ΔG<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL2(NO3)](NO3)2-BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL2(NO3)](NO3)2 in aqueous solution. Moreover, the interaction between [PrL2(NO3)](NO3)2 and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL2(NO3)](NO3)2 with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL2(NO3)](NO3)2 can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.