The spontaneous release of a high-molecular-weight aggregate containing immunoglobulin G from the surface of Ehrlich ascites tumor cells

The spontaneous release of tumor cell antigens from the cell surface into the circulation has been proposed as a mechanism whereby tumors may escape the immune response of the host. In this study we have found that Ehrlich ascites tumor cells after removal from the host (mouse) spontaneously release significant amounts of cell surface components during incubation for 1 h in cold isotonic buffer. Immunodiffusion studies revealed that immunoglobulin G (IgG) and a complement component (C3) are included in this spontaneously released material. These surface-bound humoral immune components are apparently released in the form of a high-molecular-weight aggregate (cell coat particle) as shown by ultracentrifugation and ultrafiltration experiments. Precipitation of IgG from the cell coat particle preparation with antibodies directed against mouse IgG followed by detergent gel electrophoresis of the immune precipitate revealed five major bands in addition to the heavy and light chains of IgG. These results suggest that host IgG is tightly bound to several other components at the cell surface, perhaps in the form of immune complexes. IgG is localized on the tumor cell surface in a highly heterogenous pattern with the appearance of patches and caps in some cells as shown by immunofluorescence analysis. The possibility that humoral immune components bind to the tumor cell surface and result in the shedding of high-molecular-weight aggregates of cell surface antigens into extracellular fluids is discussed.     

Spontaneous formation of platinum particles on electrodeposited palladium

Pt particles have been spontaneously formed on the electrochemically deposited Pd layer on ITO substrate. SEM reveals that the Pt particles spontaneously formed on the Pd surface are uniformly distributed. The as-prepared material (denotes as Pt–Pd/ITO) as electrode shows a higher activity for ethanol oxidation than that of Pd/ITO. The mechanism is tentatively explained as that the H dehydrogenated from ethanol on Pt can efficiently spillover to the underneath Pd, resulting in an enhanced kinetics. The rapid removal of H on the Pt active sites accelerates the further adsorption of ethanol and dehydrogenation (oxidation). This work demonstrates a strategic method to spontaneous prepare small particles on the reductive species-containing substrates. The metal ion with a higher standard potential than that of hydrogen is theoretically possible to be spontaneously reduced to metal on hydrogenated Pd.     

Sodium alginate/HPMC/liquid paraffin emulsified (o/w) gel beads,by factorial design approach; and in vitro analysis

The present study involved development of a novel sodium alginate (SA)/HPMC/light liquid paraffin emulsified (o/w) gel beads containing Diclofenac sodium (DS) as an active pharmaceutical ingredient and its site specific delivery by using hard gelatin capsule fabricated by enteric coated Eudragit L-100 polymer. Emulsified gel beads were formulated by 3-level factorial design, ionic gelatin method. The obtained beads were characterized by Fourier transform infrared, X-ray diffraction and Field emission scanning electron microscope analysis. The variables such as SA (X₁), HPMC (X₂), were optimized for drug loading and in vitro drug release with the help of response surface methodology (RSM). The RSM analysis predicted that SA was significant for both drug loading (p = 0.0005) and drug release (p = 0.0041). HPMC was only significant for drug release (p = 0.0154). The cross-product contribution (2FI) and quadratic model were found to be adequate and statistically accurate with correlation value (R²) of 0.9054 and 0.9450 to predict the drug loading and drug release respectively. An increase in concentration of HPMC and SA decreases the drug loading as well as the drug release. The obtained optimum values of drug loading and DS released were 7.43 % and 85.54 % respectively, which were well in agreement with the predicted value by RSM.     

Kinetics of proton release after flash photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) in aqueous solution

The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at approximately 400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the nitronic acid) is followed by a slower (tau approximately 63 +/- 6 ns) phase (deprotonation of the nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 degrees C the aci-nitro decay rate is 18 +/- 4 s(-1). Protons are released to the solution with rate (1.58 +/- 0.09) x 10(7) s(-1) at neutral pH from the nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pK(a) of the nitronic acid as 3.69 +/- 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, with the slower phase being characterized by an apparent rate constant strongly dependent on the pH. The strongly acidic character of the final photoproduct (sulfate ion) means that there is negligible buffering of photoreleased protons.     

Effects of soluble fractions from untreated and SiO2-treated subcellular particles of macrophages on nucleic acid metabolism in isolated nuclei of experimental granulation tissue.

Nuclei isolated from proliferating granulation tissue were incubated with 20 000 g supernatants from untreated and SiO2-treated subcellular particles of rat peritoneal macrophages in the presence of radioactive nucleic acid precursors. The supernatant from SiO2-treated subcellular particles increased the incorporation of [3H]CTP into nuclear RNA maximally by 26% at 5 min, and that of [methyl-3H]dTTP into DNA by 16% at 20 min. The release of radioactivity from labeled DNA was suppressed simultaneously. An RNase preparation from rat peritoneal macrophages enhanced the release of radioactivity from labeled DNA similarly as the soluble fraction from untreated subcellular particles of macrophages. The results suggest that the effects of the soluble fractions upon DNA metabolism of granuloma cells are at least partly independent of the effects on RNA metabolism and that the soluble fraction from SiO2-treated subcellular particles of macrophages stabilizes DNA through inhibition of nuclease activity.     

Improved hydrogen release from LiB0.33N0.67H2.67 with noble metal additions

The hydrogen release behavior of the quaternary hydride LiB(0.33)N(0.67)H(2.67) has been successfully improved through the incorporation of small quantities of noble metal. Adding 5 wt % Pd either as Pd metal particles or as PdCl(2) reduced the temperature T(1/2) corresponding to the midpoint of the hydrogen release reaction by DeltaT(1/2) = -43 degrees C and -76 degrees C, respectively. PtCl(2) and Pt nanoparticles supported on a Vulcan carbon substrate proved to be even more effective, with DeltaT(1/2) = -90 degrees C. The amount of NH(3) released during dehydrogenation is reduced compared to that from additive-free material, and, more importantly, at temperatures below 210 degrees C hydrogen is released with no detectable NH(3). In contrast to additive-free LiB(0.33)N(0.67)H(2.67), which melts completely above 190 degrees C and releases hydrogen from the liquid state only above approximately 250 degrees C, hydrogen release from LiB(0.33)N(0.67)H(2.67) + 5 wt % Pt/Vulcan carbon is accompanied by partial melting plus a cascade through a series of solid intermediate phases. Calorimetric measurements indicate that both additive-free and Pt-added LiB(0.33)N(0.67)H(2.67) release hydrogen exothermically, and hence the reverse reaction is thermodynamically unfavorable. By exposing partially dehydrogenated samples to high H(2) pressures at modest temperatures, fractional hydrogen uptake (roughly 15% of the released hydrogen) has been achieved. The mechanism by which noble metals promote hydrogen release is not known, but the behavior is consistent with that expected for a catalyst, including a large effect with small additions and saturation of the effect at low concentration.     

Photoactivation of amino-substituted 1,4-benzoquinones for release of carboxylate and phenolate leaving groups using visible light

Upon exposure to visible light, 2-pyrrolidino-substituted 3,6-dimethyl-1,4-benzoquinones photocyclize to give benzoxazolines with quantum yields of 0.07-0.10 in CH2Cl2, 0.02-0.04 in CH3CN, and <0.01 in 30% aq CH3CN. With carboxylate or phenolate leaving groups incorporated via coupling to a 5-hydroxymethyl group of the quinones, the photocyclizations give benzoxazolines that eliminate the leaving groups in a dark reaction. Lifetimes for elimination of 4-YC6H4OH in 30% phosphate buffer in CD3CN (pD 7) at 17 degrees C are 13.1, 0.54, and 0.13 h for Y = H, CF3, and CN, respectively, and the linear equation log k (h(-1)) = 0.998(-pKa) + 8.80 gives a best fit to the data. Carboxylate leaving groups are rapidly eliminated upon photolysis of the quinones in aq CH3CN to produce an o-quinone methide intermediate that is trapped by 4 + 2 cycloaddition with unreacted starting material or with added 3-(dimethylamino)-5,5-dimethyl-2-cyclohexen-1-one. The ortho-quinone methide is observed at 339 and 455 nm by conventional absorption spectroscopy and gives a pseudo-first-order fit of the decay kinetics with tau1/2 = 34.9 min in 30% phosphate buffer in CH3CN at 20 degrees C.     

Carboxymethylcellulose-coated magnesium-layered hydroxide nanocomposite for controlled release of 3-(4-methoxyphenyl)propionic acid

Carboxymethylcellulose (CMC) acts as a coating material for a magnesium-layered hydroxide-3-(4-methoxyphenyl)propionate (MLH-MPP) nanocomposite via spontaneous self-assembly. The resulting product is called a magnesium-layered hydroxide-3-(4-methoxyphenyl)propionate/carboxymethylcellulose (MLH-MPP/CMC) nanocomposite. The XRD pattern of the MLH-MPP/CMC nanocomposite showed that MPP was maintained in the interlayers of the MLH, thus confirming that CMC is only deposited on the surface of the MLH-MPP nanocomposite. These findings were also supported by FTIR spectra, SEM and TEM. TGA data showed that the thermal stability of the intercalated MPP was significantly enhanced compared to pure MPP and uncoated nanocomposite. The release of MPP from the interlayers of MLH-MPP/CMC nanocomposite showed slower release than did uncoated nanocomposite and followed pseudo–second-order kinetics. Since the herbicide, MPP was released from the synthesised nanocomposite in a sustained manner, thus, it has excellent potential to be used as a controlled-release herbicide formulation.     

Label‐Free Measurements of the Diffusivity of Molecules in Lipid Membranes

An important and characteristic property of a cell membrane is the lateral mobility of protein molecules in the lipid bilayer. This has conventionally been measured by labeling the molecules with fluorescent markers and monitoring their mobility by different fluorescence‐based techniques. However, adding the label to the studied molecule may affect the system, so it is an assumption in almost all experiments that the measured mobility of the biomolecule with its label is the same as that of the unlabeled molecule. However, this assumption is rarely tested due to a lack of suitable methods. In this work, a new technique to perform label‐free diffusivity measurements is developed and used to measure the effect of the label for two common protein–lipid systems: 1) streptavidin (SA) coupled to a supported lipid bilayer (SLB) through biotinylated lipids and 2) the extracellular part of the T‐cell adhesion protein CD2, coupled to an SLB through histidine tags to nickel‐chelating lipids. A measurable (≈12 %) decrease in diffusivity is found for both labeled proteins, even though the molecular mass of the label is almost 100 times smaller than those of the proteins (≈50 kDa). The results illustrate the importance of being able to study different biophysical properties of cell membranes and their mimics without relying on fluorescent labels, especially if fluorescent labeling is difficult or is expected to affect the nature of the intermolecular interactions being studied.     

Surface interactions and quantum kinetic molecular sieving for H2 and D2 adsorption on a mixed metal-organic framework material

A rational strategy has been used to immobilize open metal sites in ultramicroporosity for stronger binding of multiple H 2 molecules per unsaturated metal site for H 2 storage applications. The synthesis and structure of a mixed zinc/copper metal-organic framework material Zn 3(BDC) 3[Cu(Pyen)] .(DMF) 5(H 2O) 5 (H 2BDC = 1,4 benzenedicarboxylic acid and PyenH 2 = 5-methyl-4-oxo-1,4-dihydro-pyridine-3-carbaldehyde) is reported. Desolvation provides a bimodal porous structure Zn 3(BDC) 3[Cu(Pyen)] (M'MOF 1) with narrow porosity (<0.56 nm) and an array of pores in the bc crystallographic plane where the adsorbate-adsorbent interactions are maximized by both the presence of open copper centers and overlap of the potential energy fields from pore walls. The H 2 and D 2 adsorption isotherms for M'MOF 1 at 77.3 and 87.3 K were reversible with virtually no hysteresis. Methods for determination of the isosteric enthalpies of H 2 and D 2 adsorption were compared. A virial model gave the best agreement (average deviation <1 standard deviation) with the isotherm data. This was used in conjunction with the van't Hoff isochore giving isosteric enthalpies at zero surface coverage of 12.29 +/- 0.53 and 12.44 +/- 0.50 kJ mol (-1) for H 2 and D 2 adsorption, respectively. This is the highest value so far observed for hydrogen adsorption on a porous material. The enthalpy of adsorption, decreases with increasing amount adsorbed to 9.5 kJ mol (-1) at approximately 1.9 mmol g (-1) (2 H 2 or D 2 molecules per Cu corresponding to adsorption on both sides of planar Cu open centers) and is virtually unchanged in the range 1.9-3.6 mmol g (-1). Virial analysis of isotherms at 87.3 K is also consistent with two H 2 or D 2 molecules being bound to each open Cu center. The adsorption kinetics follow a double exponential model, corresponding to diffusion along two types of pores, a slow component with high activation energy (13.35 +/- 0.59 kJ mol (-1)) for the narrow pores and a faster component with low activation energy (8.56 +/- 0.41 kJ mol (-1)). The D 2 adsorption kinetic constants for both components were significantly faster than the corresponding H 2 kinetics for specific pressure increments and had slightly lower activation energies than the corresponding values for H 2 adsorption. The kD 2/ kH 2 ratio for the slow component was 1.62 +/- 0.07, while the fast component was 1.38 +/- 0.04 at 77.3 K, and the corresponding ratios were smaller at 87.3 K. These observations of kinetic isotope quantum molecular sieving in porous materials are due to the larger zero-point energy for the lighter H 2, resulting in slower adsorption kinetics compared with the heavier D 2. The results show that a combination of open metal centers and confinement in ultramicroporosity leads to a high enthalpy for H 2 adsorption over a wide range of surface coverage and quantum effects influence diffusion of H 2 and D 2 in pores in M'MOF 1.     

麦饭石含量对载药复合凝胶小球释药性能的影响

以瓜尔胶-g-聚丙烯酸/麦饭石复合水凝胶(GG-g-PAA/MS)和海藻酸钠(SA)为原料,双氯芬酸钠(DS)为模拟药物,采用离子凝胶法制备了载药复合凝胶小球,考察了pH敏感性以及MS含量对复合凝胶小球的包封率、载药率、溶胀性和药物释放行为的影响.结果表明:凝胶小球具有明显的pH敏感性,在不同pH介质中溶胀率和释放速率...     

Femtosecond/picosecond time-resolved fluorescence study of hydrophilic polymer fine particles

Femtosecond/picosecond time-resolved fluorescence study of hydrophilic polymer fine particles (polyacrylamide, PAAm) was reported. Ultrafast fluorescence dynamics of polymer/water solution was monitored using a fluorescent probe molecule (C153). In the femtosecond time-resolved fluorescence measurement at 480 nm, slowly decay components having lifetimes of tau(1) approximately 53 ps and tau(2) approximately 5 ns were observed in addition to rapid fluorescence decay. Picosecond time-resolved fluorescence spectra of C153/PAAm/H2O solution were also measured. In the time-resolved fluorescence spectra of C153/PAAm/H2O, a peak shift from 490 to 515 nm was measured, which can be assigned to the solvation dynamics of polymer fine particles. The fluorescence peak shift was related to the solvation response function and two time constants were determined (tau(3) approximately 50 ps and tau(4) approximately 467 ps). Therefore, the tau(1) component observed in the femtosecond time-resolved fluorescence measurement was assigned to the solvation dynamics that was observed only in the presence of polymer fine particles. Rotational diffusion measurements were also carried out on the basis of the picosecond time-resolved fluorescence spectra. In the C153/PAAm/H2O solution, anisotropy decay having two different time constants was also derived (tau(6) approximately 76 ps and tau(7) approximately 676 ps), indicating the presence of two different microscopic molecular environments around the polymer surface. Using the Stokes-Einstein-Debye (SED) equation, microscopic viscosity around the polymer surface was evaluated. For the area that gave a rotational diffusion time of tau(6) approximately 76 ps, the calculated viscosity is approximately 1.1 cP and for tau(7) approximately 676 ps, it is approximately 10 cP. The calculated viscosity values clearly revealed that there are two different molecular environments around the polyacrylamide fine particles.     

Indirect, reversible high-density hydrogen storage in compact metal ammine salts

The indirect hydrogen storage capabilities of Mg(NH 3) 6Cl 2, Ca(NH 3) 8Cl 2, Mn(NH 3) 6Cl 2, and Ni(NH 3) 6Cl 2 are investigated. All four metal ammine chlorides can be compacted to solid tablets with densities of at least 95% of the crystal density. This gives very high indirect hydrogen densities both gravimetrically and volumetrically. Upon heating, NH 3 is released from the salts, and by employing an appropriate catalyst, H 2 can be released corresponding to up to 9.78 wt % H and 0.116 kg H/L for the Ca(NH 3) 8Cl 2 salt. The NH 3 release from all four salts is investigated using temperature-programmed desorption employing different heating rates. The desorption is found mainly to be limited by heat transfer, indicating that the desorption kinetics are extremely fast for all steps. During desorption from solid tablets of Mg(NH 3) 6Cl 2, Mn(NH 3) 6Cl 2, and Ni(NH 3) 6Cl 2, nanoporous structures develop, which facilitates desorption from the interior of large, compact tablets. Density functional theory calculations reproduce trends in desorption enthalpies for the systems studied, and a mechanism in which individual chains of the ammines are released from the surface of the crystal is proposed to explain the fast absorption/desorption processes.     

Single cell determination of nitric oxide release using capillary electrophoresis with laser-induced fluorescence detection

Measurements of nitric oxide (NO) release at single cell level are fundamental to understand the diverse physiological functions of this remarkable molecule. To achieve this purpose, capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was originally described for the sensitive determination of NO release in individual neuron and mammalian cell after 8-(3,4-diaminophenyl)-2,6-bis(2-carboxyethyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (DAMBO-P(H)) was chosen as the fluorescent probe. Various parameters affecting NO trapping in vivo and CE separation were systematically studied. Under the optimal conditions, complete and fast separation of the resulted targeted high-fluorescent triazole (DAMBO-P(H)-T) was achieved in about 3 min (2.89 min), and the relative standard deviations (RSDs) values of migration time and peak area were less than 5% and 9% for intra-day and inter-day assays, respectively. The detection limit was 42 amol (at a signal-to-noise ratio of 3). The feasibility of application of the developed method was validated by successfully applied to the measurements of NO release from four single cell study models. This original application of this method in diverse samples represents a powerful tool to study the kinetics of NO release by neuronal cells during neurotransmission, as well as for the understanding of the pathobiological and therapeutic basis of this molecule for cardiovascular diseases and under oxidative stress.     

Control of dopants/modifiers in differential mobility spectrometry using a piezoelectric injector

A piezoelectric injector has been interfaced to a differential mobility spectrometer to enable fast and reversible control of dopant/transport-gas modifier levels within the reaction region of the instrument. Operating at 1 Hz with optimised bipolar waveforms for the piezoelectric injector and gas flows within the injector, steady-state 2-butanol mass fluxes of 21 to 1230 ng min(-1) and 1-bromohexane mass fluxes of 149 to 2644 ng min(-1) were delivered to the differential mobility cell. Control of split-flow and transport-gas flow rates enabled rapid and flexible control of the dopant concentrations. The system was consistently reproducible with a relative standard deviation (RSD) of 7.9% at every mass- flux level studied. Stable responses were achieved between 3 to 5 s following a change in the control levels and no significant hysteresis effects were observed. In the positive mode it was possible to control the extent of formation protonated monomer and proton bound cluster ions, tentatively assigned to{C(4)H(9)OH(H(2)O)(n)H}(+) and {(C(4)H(9)OH)(2)(H(2)O)(n)H}(+) and similar control was possible in the negative mode where the concentration relationship for the formation of bromide clusters indicated the presence of multiple ionisation mechanisms. A dopant formulation for the simultaneous control of ions in both the positive and negative modes was demonstrated by the injection of a 50%/50% v/v solution of 2-butanol/1-bromohexane with mass fluxes of 2-butanol in the mixture of between 11 and 1161 ng min(-1) and between 13 and 1325 ng min(-1) for 1-bromohexane.     

Poly(2-hydroxyethyl acrylate) hydrogels containing hyper-branched poly(amidoamine) for sustained drug release

Hydrogels containing hyper-branched poly(amidoamine) (hb-PAMAM) microenvironments were suggested for the sustained release of ionizable drugs. For this purpose, a series of poly(2-hydroxyethyl acrylate) (PHEA) hydrogels containing hb-PAMAM (PHEA-hb-PAMAM) were prepared by copolymerization of 2-hydroxyethyl acrylate with acryl-terminated hb-PAMAM. The hb-PAMAM was synthesized by the Michael addition reaction of triacryloylhexahydro-1,3,5-triazine (TT) and piperzaine (PZ). By using nonionic Tegafur and ionizable salicylic acid (SA) as model drugs, the release mechanisms of drugs from PHEA-hb-PAMAM hydrogels were investigated. Compared with the release kinetic of Tegafur, the release rate of SA from the hydrogels was evidently slowed down. Moreover, the release rate of SA can be modulated by the addition of salt. This can be attributed to the ionic interaction of SA with hb-PAMAM microenvironments. By analyzing the release kinetics of SA from the hydrogels, it was found that the release of SA followed non-Fickian diffusion.     

Evolution of Stabilized 1T-MoS2 by Atomic-Interface Engineering of 2H-MoS2/Fe−Nx towards Enhanced Sodium Ion Storage

Metallic conductive 1T phase molybdenum sulfide (MoS₂) has been identified as promising anode for sodium ion (Na⁺) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic-interface engineering is employed for constructing 2H-MoS₂ layers assembled on single atomically dispersed Fe−N−C (SA Fe−N−C) anode material that boosts its reversible capacity. The work-function-driven-electron transfer occurs from SA Fe−N−C to 2H-MoS₂ via the Fe−S bonds, which enhances the adsorption of Na⁺ by 2H-MoS₂, and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS₂ with the ferromagnetic spin-polarization of SA Fe−N−C occurs during the sodiation/desodiation process, which significantly enhances the Na⁺ storage kinetics, and thus the 1T/2H MoS₂/SA Fe−N−C display a high electronic conductivity and a fast Na⁺ diffusion rate.     

Highly efficient circulating tumor cell isolation from whole blood and label-free enumeration using polymer-based microfluidics with an integrated conductivity sensor

A novel microfluidic device that can selectively and specifically isolate exceedingly small numbers of circulating tumor cells (CTCs) through a monoclonal antibody (mAB) mediated process by sampling large input volumes (>/=1 mL) of whole blood directly in short time periods (<37 min) was demonstrated. The CTCs were concentrated into small volumes (190 nL), and the number of cells captured was read without labeling using an integrated conductivity sensor following release from the capture surface. The microfluidic device contained a series (51) of high-aspect ratio microchannels (35 mum width x 150 mum depth) that were replicated in poly(methyl methacrylate), PMMA, from a metal mold master. The microchannel walls were covalently decorated with mABs directed against breast cancer cells overexpressing the epithelial cell adhesion molecule (EpCAM). This microfluidic device could accept inputs of whole blood, and its CTC capture efficiency was made highly quantitative (>97%) by designing capture channels with the appropriate widths and heights. The isolated CTCs were readily released from the mAB capturing surface using trypsin. The released CTCs were then enumerated on-device using a novel, label-free solution conductivity route capable of detecting single tumor cells traveling through the detection electrodes. The conductivity readout provided near 100% detection efficiency and exquisite specificity for CTCs due to scaling factors and the nonoptimal electrical properties of potential interferences (erythrocytes or leukocytes). The simplicity in manufacturing the device and its ease of operation make it attractive for clinical applications requiring one-time use operation.     

Ruthenium-catalyzed dehydrogenation of ammonia boranes

The dehydrogenation of ammonia borane (AB) and methylammonia borane (MeAB) is shown to be catalyzed by several Ru-amido complexes. Up to 1 equiv of H2 (1.0 system wt %) is released from AB by as little as 0.03 mol % Ru within 5 min, and up to 2 equiv of H2 (3.0 system wt %) are released from MeAB with 0.5 mol % Ru in under 10 min at room temperature, the first equivalent emerging within 10 s. Also, a mixture of AB/MeAB yields up to 3.6 system wt % H2 within 1 h with 0.1 mol % Ru. Computational studies were performed to elucidate the mechanism of dehydrogenation of AB. Finally, it was shown that alkylamine-boranes can serve as a source of H2 in the Ru-catalyzed reduction of ketones and imines.     

Fluorescence imaging for in situ detection of cell surface sialic acid by competitive binding of 3-(dansylamino)phenylboronic acid

Sialic acid (SA) usually locates at the terminal position of the sugar chains on cell membranes, and its expression level is closely associated with cancer. Here polysialic acid (PSA) embedded gold nanoparticles (AuNPs) were prepared and functionalized with fluorescent 3-(dansylamino)phenylboronic acid (DAPB) for in situ imaging and detection of cell surface SA. The fluorescence resonance energy transfer (FRET) from DAPB to AuNPs quenched the fluorescence of DAPB. In the presence of additional SA or SA-abundant cells, the competitive binding of DAPB with SA and PSA led to the release of the assembled DAPB from the surface of PSA-embedded AuNPs, resulting in fluorescence of DAPB on SA-abundant cell surface. The proposed methods realized the in situ imaging and monitoring of cell surface SA, and could also be applied to the quantification of cell number and the amounts of cell surface SA. This work not only proposed a convenient visualization method for the analysis of SA on cell membranes, but also provided a potential tool for accelerating the elucidation of the basic role of SA in various biological processes and development of anti-cancer therapies.