A general strategy for one-step fabrication of biocompatible microcapsules with controlled active release

Fabrication of biocompatible core-shell microcapsules in a controllable and scalable manner remains an important but challenging task.Here,we develop a one-step microfluidic approach for the highthroughput production of biocompatible microcapsules,which utilizes single emulsions as templates and controls the precipitation of biocompatible polymer at the water/oil interface.The facile method enables the loading of various oils in the core and the enhancement of polymer shell strength by polyelectrolyte coating.The resulting microcapsules have the advantages of controllability,scalability,biocompatibility,high encapsulation efficiency and high loading capacity.The core-shell microcapsules are ideal delivery vehicles for programmable active release and various controlled release mechanisms are demonstrated,including burst release by vigorous shaking,pH-triggered release for targeted intestinal release and sustained release of perfume over a long period of time.The utility of our technique paves the way for practical applications of core-shell microcapsules.     

Mass transfer coupled with the relaxation of a polymeric matrix: A controlled release process

A solution to Fick's equation is presented which accurately predicts the transfer of mass out of a polymeric rod or sheet undergoing relaxation by a solvent permeating it by Case II transport. There is a critical length. Before the solvent permeates to this length the diffusible material can diffuse away from the moving boundary faster than it is becoming available at the boundary. Afterward the reverse is true. Five sets of experimental data from three different sources have been used to test the model. The agreement is excellent.     

Postcolumn derivatization of amino acids using reaction flow chromatography columns with fluorescence detection: A fast new approach to selective derivatization techniques

Reaction flow (RF) chromatography with fluorescamine reagent and fluorescence detection (FLD) was used for the analysis of amino acids. The performance of RF chromatography was tested against several optimized conventional postcolumn derivatization (PCD) methods. RF columns achieved greater sensitivity compared to conventional PCD methods, without the need for reaction loops, which resulted in more efficient separations. The RF-PCD method also achieved limits of detection (LOD) from the low picomole to subnanomole range. The calibration data of the RF-PCD technique yielded R²?≥?0.99 and % relative standard deviation in peak areas ranging from 0.34% to 5%. Through reaction flow chromatography, multiplexed detection was also achieved allowing the monitoring and analysis of derivatized and nonderivatized flow streams simultaneously.     

A facile approach to prepare hybrid nanoparticles with morphology controlled by the thickness of glyco-shell

Herein, we designed a novel amphiphilic triblock glycopolymer poly(oligo(ethyleneglycol) methacrylate)-block-poly(maltopyranoside methacrylate)-block-polystyrene(POMA-b-PMal-b-PS) via the combination of reversible addition-fragmentation chain transfer(RAFT) polymerization and postpolymerization modification. The micelles with core–shell–corona structures were prepared by direct self-assembly of this glycopolymer in water. We found that these micelles can be used in in situ formation and stabilization of Au NPs. By controlling the thickness of glyco-shell, we successfully obtained Janus particles and raspberry-like particles with Au NPs in the sugar shell.     

A mesoporous silica nanosphere-based carrier system with chemically removable CdS nanoparticle caps for stimuli-responsive controlled release of neurotransmitters and drug molecules

An MCM-41 type mesoporous silica nanosphere-based (MSN) controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide (CdS) nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN mesoporous framework. We studied the stimuli-responsive release profiles of vancomycin- and adenosine triphosphate (ATP)-loaded MSN delivery systems by using disulfide bond-reducing molecules, such as dithiothreitol (DTT) and mercaptoethanol (ME), as release triggers. The biocompatibility and delivery efficiency of the MSN system with neuroglial cells (astrocytes) in vitro were demonstrated. In contrast to many current delivery systems, the molecules of interest were encapsulated inside the porous framework of the MSN not by adsorption or sol-gel types of entrapment but by capping the openings of the mesoporous channels with size-defined CdS nanoparticles to physically block the drugs/neurotransmitters of certain sizes from leaching out. We envision that this new MSN system could play a significant role in developing new generations of site-selective, controlled-release delivery nanodevices.     

A combinatorial approach to minimal peptide models of a metalloprotein active site

Screening of a "one-bead-one-compound" peptide library containing biomimetic His/Cys ligands has led to the discovery of sequences that hydrolyze ester substrates in combination with Zn2+.     

Precolumn derivatization with glyoxal as a new approach to the highly sensitive HPLC-UV determination of unsymmetrical dimethylhydrazine

A procedure has been developed for the determination of unsymmetrical dimethylhydrazine (UDMH) based on precolumn derivatization with glyoxal and determination of the produced derivative, mono-1,1-dimethylhydrazone of glyoxal, by reversed-phase HPLC (RP-HPLC) with UV detection at 305 nm. It has been demonstrated that the reaction of UDMH with an excess of glyoxal in solution quantitatively yields one stable product within 20 min at 25°C at pH 3.5. To increase the sensitivity of UDMH determination it has been proposed to perform solid-phase extraction preconcentration of the derivative from a 25-mL sample portion on cartridges containing Strata SDB-L polymer adsorbent. The analytical range of UDMH determination in water is 0.5–10000 μg/L or 0.01–20 μg/L using preconcentration. The relative standard deviations of UDMH determination (n = 3) do not exceed 0.12 and 0.25 without and with preconcentration, respectively. The accuracy of UDMH determination is confirmed by the analysis of spiked samples and by RP-HPLC determination with preliminary derivatization with 4-nitrobenzaldehyde as independent method.     

A general approach to medium ring alkynes by using metathesis of cobalt hexacarbonyl containing dienes

The assembly of medium sized rings (7-9) was achieved by using the metathesis of dienes linked by a cobalt hexacarbonyl complexed alkyne with either Grubbs' or Schrock's catalysts. The products of metathesis were subjected to transformations involving the dicobalt hexacarbonyl complexes, for example, decomplexation to liberate cyclic alkynes or Pauson-Khand reaction.     

A general approach to the screening and confirmation of tryptamines and phenethylamines by mass spectral fragmentation

Certain characteristic fragmentations of tryptamines (indoleethylamine) and phenethylamines are described. Based on the GC-EI/MS, LC-ESI/MS and MALDI/TOFMS, the mass fragmentations of 13 standard compounds, including alpha-methyltryptamine (AMT), N,N-dimethyltryptamine (DMT), 5-methoxy-alpha-methyltryptamine (5-MeO-AMT), N,N-diethyltryptamine (DET), N,N-dipropyltryptamine (DPT), N,N-dibutyltryptamine (DBT), N,N-diisopropyltryptamine (DIPT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT), methamphetamine (MAMP), 3,4-methylenedioxyamphetamine (3,4-MDA), 3,4-methylenedioxymethamphetamine (3,4-MDMA) and 2-methylamino-1-(3,4-methylenedioxyphenyl)butane (MBDB), were compared. As a result, the parent ions of these analytes were hard to be obtained by GC/MS whereas the protonated molecular ions can be observed clearly by means of ESI/MS and MALDI/TOFMS. Furthermore, two major characteristic fragmentations, namely and alpha-cleavage ([M+H](+)-->[3-vinylindole](+)) and beta-cleavage ([M+H](+)-->[CH(2)N(+)R(N1)R(N2)]), are produced when the ESI and MALDI modes are used, respectively. In the case of ESI/MS, the fragment obtained from alpha-cleavage is the major process. In contrast to this, in the case of MALDI/TOFMS, the major fragment is produced via beta-cleavage. The ionization efficiency and fragments formed from either alpha- or beta-cleavages are closely related to the degree of alkylation of the side chain nitrogen in both cases.     

A covalently bonded AlQ3/SiO2 hybrid material with blue light emission by a conventional sol-gel approach

We report the design and synthesis of a covalently bonded AlQ3/SiO2 hybrid material with strong blue light emission by a sol-gel approach, which make AlQ3 solution-processable and chemically stable.     

Sensitive measurement of methylene blue active substances by attenuated total reflection spectrometry with a trimethylsilane-modified glass slab optical waveguide

Attenuated total reflection spectrometry with a slab optical waveguide (SOWG) was explored for the simple, rapid and sensitive measurement of total anionic surfactants by the methylene blue active substance (MBAS) method. A fused-silica sheet used as a guiding layer was modified with trimethylsilane (TMS) to extract and concentrate the MBASs on the SOWG surface. Based on preliminary studies of the adsorption behavior and visible ATR spectrum of MB on the modified silica surface, a detection wavelength of 600 nm was chosen for the sensitive measurement of anionic surfactants. When the concentration of MB was set at 10 microM in the final measurement solution, the calibration curve for a typical anionic surfactant (sodium dodecylbenzenesulfonate) was linear up to 0.6 microM and the detection limit was 0.07 microM. The proposed method was applied to the determination of total anionic surfactants in river water.     

A convenient approach to chiral sulfoxides by enantioselective oxidation with a steroidal furylhydroperoxide

The introduction of a steroidal residue into a position distant from the reaction center shows a beneficial effect on the reactivity of secondary furylhydroperoxides: chiral sulfoxides are obtained by asymmetric oxidation of sulfides and/or kinetic resolution of racemic sulfoxides with reduced reaction times and high enantiomeric excesses.     

A theoretical approach to the photochemical activation of matrix isolated aluminum atoms and their reaction with methane

The photochemical activation of Al atoms in cryogenic matrices to induce their reaction with methane has been experimentally studied before. Here, a theoretical study of the nonadiabatic transition probabilities for the ground ((2)P:3s(2)3p(1)) and the lowest excited states ((2)S:3s(2)4s(1) and (2)D:3s(2)3d(1)) of an aluminum atom interacting with a methane molecule (CH(4)) was carried out through ab initio Hartree-Fock self-consistent field calculations. This was followed by a multiconfigurational study of the correlation energy obtained by extensive variational and perturbational configuration interaction analyses using the CIPSI program. The (2)D state is readily inserted into a C-H bond, this being a prelude to a sequence of avoided crossings with the initially repulsive (to CH(4)) lower lying states (2)P and (2)S. We then use a direct extension of the Landau-Zener theory to obtain transition probabilities at each avoided crossing, allowing the formation of an HAlCH(3) intermediate that eventually leads to the final pair of products H+AlCH(3) and HAl+CH(3).     

Description of the adsorption equilibrium of organic substances absorbed from a flow of moist air by a fixed bed of active carbon moistened to equilibrium

Isotherms of the adsorption of benzene vapor from moist air on active carbon (AC) moistened to equilibrium are obtained from dynamic experiments. The experimental data on the adsorption equilibrium of some organic substances from a flow of moist air by a fixed bed of AC moistened to equilibrium are obtained. The data on the equilibrium adsorption of benzene vapor is analyzed using the Dubinin-Radushkevich equation (the theory of volume filling of micropores). It is revealed that the characteristic adsorption energy of benzene vapor decreases as the filling of the microporous volume with water molecules increases. The characteristic adsorption energy depends on the following factors: polarizability of a substance in the adsorption field created by micropores, the number of carbon atoms in the adsorbate molecules, and parameters of the porous structure. The equation for the calculation of the parameters of equilibrium adsorption of organic substances from moist air on AC moistened to equilibrium are obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 434–438, March, 1995.     

Cocyclotrimerization of 6-alkynylpurines with alpha,omega-diynes as a novel approach to biologically active 6-arylpurines

Transition metal complex catalyzed cocyclotrimerization of 6-alkynylpurines 1 with various diynes enables the preparation of a plethora of substituted 6-arylpurines 3 in good yields. The most general catalyst for the reaction is a user-friendly system based on a nickel-phosphine complex and reductant (NiBr(2)(dppe)/Zn) in MeCN. The reaction conditions are compatible with various protective groups on the purine moiety (Bn, THP). As far as other potential catalysts were concerned, only CoBr(PPh(3))(3) showed reasonable activity in cocyclotrimerization of alkynylpurines with dipropargyl ether. A comparison of catalytic with stoichiometric approaches and the ligand effect in the catalyst is also given. Cytostatic activity screening of title 6-arylpurines was performed and several moderately active compounds were found.     

A stereoselective approach to optically active butenolides by Horner–Wadsworth–Emmons olefination reaction of α-hydroxy ketones

Di- and trisubstituted butenolides and tricyclic unsaturated lactones, of high enantiomeric excess were prepared via the efficient sequential esterification Horner–Wadsworth–Emmons reaction of enantiomerically enriched 2-hydroxy-substituted phenones and aromatic cyclic α-hydroxy ketones in good yield.