Taste masking is an important strategy for improving adherence of patients, especially children, who have to take pharmaceutical drugs with a bitter taste, as is the case of praziquantel (PZQ) used to treat schistosomiasis. In this work, a modified interfacial polymer deposition method was used to prepare polymer microcapsules and microspheres to encapsulate PZQ, where formulations were optimized to fulfill the stringent requirements for controlled drug release. In vitro release tests confirmed the suitability of the formulation with microcapsules of the anionic copolymer L30D, in which the loading of PZQ was larger than 90% in solutions that were stable at low pH but released PZQ under enteric conditions. We also show that the encapsulation was effective in terms of masking PZQ taste through the analysis with an electronic tongue.
Chiral recognition abilities of tetraamide-based receptors 1 and 2 bearing l-serine and l-threonine as recognition sites, respectively, and terminal pyrenyl groups as signaling units for enantiomers of biologically important N-acetyl amino acid tetrabutylammonium salts were studied in acetonitrile. The receptors showed ratiometric fluorescence changes upon the addition of chiral guest anions. The binding constants for amino acid derivatives were in the 104–105 mol−1 dm3 range. The chiral discrimination abilities (K11,D/K11,L) of 1 and 2 were significantly large, for instance K11,D/K11,L for Ac-Leu-O− were found to be 3.9 and 4.6, respectively. The complex structures were evaluated by 1H NMR titrations and DFT calculations implying that the effective hydrogen bond formations by six N-H and O-H groups and a CH-π interaction of the acetyl group of d-enantiomer with a terminal pyrenyl group of the receptor.
The speciation and coordination geometries of M(III)-citrate complexes in aqueous solutions, where M denotes Eu, Tb, Lu, or Cm, are studied using potentiometric titration, 1H, and 13C nuclear magnetic resonance spectroscopies. Their photophysical properties are also characterized by time-resolved fluorescence spectra. The formation constants of mononuclear, dinuclear, and trinuclear Lu-citrate species, i.e., [Lu(Cit)2]3−, [Lu2(OH)2(Cit)2]2−, and [Lu3(OH)4(Cit)4]7−, were determined as 9.78 ± 0.30, 3.60 ± 0.30, and 1.02 ± 0.03, respectively, by potentiometric titration in 3.00 M NaClO4 aqueous media. Terminal carboxylic conformation in trinuclear complexes comprised both the five- and six-membered rings at different exchanging rates. Hydration states evaluated for Eu3+ ions are the chemical formula of [Eu(Cit)2(H2O)2.5]3− and [Eu3(OH)4(Cit)4(H2O)3.4]7−. These complexes in aqueous solution have geometrical similarity to the crystal structures in the literature. Furthermore, the entity of the hetero-trinuclear complex induces the intramolecular energy transfer from Tb3+ to Eu3+. The incorporation of Cm3+ into these homo/hetero-trinuclear citrate complexes proved to be a successful trial to probe the formation of actinide polymer at a trace level.
We report on immunosensors to detect D-dimer, a biomarker of venous thromboembolism, which are made with layer-by-layer (LbL) films containing immobilized anti-D-dimer monoclonal antibody alternated with a layer of chitosan/gold nanoparticles (AuNpChi). Detection was due to irreversible adsorption of the antigen D-dimer on its corresponding antibody according to a Langmuir-Freundlich model, thus giving rise to ellipsoidal structures in scanning electron microscopy images whose size and number increased with D-dimer concentration. The chemical groups involved in the adsorption process were inferred from polarization-modulated infrared reflection absorption (PM-IRRAS) through changes in the amide and carbonyl bands. Detection of D-dimer was made with electrical impedance spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The latter was the most sensitive with a detection limit of 9 × 10−4 µg/mL, sensitivity of 0.27 × 10−6 A/µgmL−1 with linear increase from 0 to 1 µg/mL. The selectivity of the immunosensor made with AuNpChi/anti-D-dimer film was verified by noting negligible changes in the cyclic voltammograms when exposed to typical interferents in biological fluids.
We have investigated the electrochemical hydrogenation of toluene using a PEM reactor for development of an organic chemical hydride system. Especially, the influence of catalyst materials such as Pt, Ru, and PtRu for a PEM reactor on the by-product formation and product selectivity in the hydrogenation of toluene was investigated.
Instructed-assembly (iAssembly or iA) refers to the formation of ordered superstructures of molecules as the consequence of at least one trigger event (e.g., a reaction or a ligand-receptor interaction). As a biomimetic process that transforms from an equilibrium to another equilibrium, iA is emerging as a powerful approach to provide spatiotemporal control for a range of potential biomedical applications, including molecular imaging, cancer therapy, and tissue engineering. This account introduces the general concept of iA in the context of cells and illustrates how to achieve iA for applications. By mainly describing the representative examples of iA and its applications in complex environments, such as cells or animals, and providing the perspectives of the future development of iA, we intend to show that, as a process that bridges self-assembly and self-organization, iA offers chemists a facile means to explore the emergent properties of molecular assemblies and the dynamics of molecular processes to control cell fate. Particularly, iA promises many wonderful surprises and useful applications in physical and/or life sciences when multiple processes (e.g., self-assembly, instructed-assembly, and self-organization) are taking place simultaneously.
Stereoisomerism is one of the most fundamental and indispensable notions in chemistry. We have recently found that a novel form of stereoisomerism emerges in cycloarylenes, cyclic arrays of aromatic panels. Structural rigidity that is a precondition for chirality has been realized in an unconventional manner with the cyclic structures, which gives rise to unique cyclostereoisomerism affording diastereomers and enantiomers. In this account, structural chemistry of cylindrical cycloarylenes synthesized in our group will be reviewed with an emphasis on stereochemistry. The relevant studies in this new field will deepen our understanding of the fundamental structural chemistry of finite single-wall carbon nanotube molecules.
To stabilize organic neutral radicals, which are usually very unstable chemical species in air atmosphere, “steric protection” is the most general and indispensable method. Based on the design of electronic-spin structure of polycyclic carbon-centered π-radicals, we have for the first time realized a peculiarly stable neutral π-radical without bulky substituent groups, 4,8,12-trioxotriangulene (TOT), whose decomposition point is higher than 240 °C in the solid state under air. This remarkably high air-stability as a neutral radical is achieved by spin-delocalization originating from the symmetric and expanded π-electronic structure of TOT. The oxo-functionalities also highly contribute to the high stability through electronic-spin modulation, where the largest electronic spin density located at the central carbon atom further decreases the spin densities of the peripheral carbon atoms. In the solution state, TOT is in the equilibrium between the monomer and highly symmetric π-dimer, as stabilized by the formation of the strong two-electron-multicenter bonding. Crystal structure analysis revealed that TOT derivatives show strong self-assembling ability forming one-dimensional columns, which further construct three-dimensional networks by multiple intercolumnar non-covalent interactions due to the absence of bulky substituent groups. Substituent groups at the apexes of the triangular carbon-framework of TOT afford variations of the π-stacking mode in the one-dimensional columns, influencing the magnetic properties and photo-absorptions around the near-infrared region. The electronic effect of the substituent groups also affects the redox potentials of TOT. The peculiarly high stability of TOT neutral radicals and their three-dimensional networks by robust intermolecular interactions achieved in our study are very beneficial for the molecular design of new polycyclic air-stable neutral radicals. Furthermore, we believe that the open-shell electronic structures of neutral π-radicals, which are quite different from those of close-shell molecular systems, will also produce milestones for the exploration of peculiar physical properties and catalytic activity for organic transformation originating from their unconventional electronic-spin nature.
Surfactants are a versatile and widely used class of molecules, due to their valuable adsorption and self-assembly properties. In particular, surfactants that can respond to stimuli are of interest in modulating wetting, controlling delivery, and exploring mechanistic aspects of biological processes. Incorporating azobenzene into surfactants is a classic approach to rendering molecules that respond to light as an external stimulus; these molecules find wide utility in the precise spatiotemporal control of dispersed systems, from DNA to graphene. More recently, the creation of diverse libraries of such molecules has been achieved by coupling azobenzene-containing hydrophobic tail-groups to hydrophilic carbohydrate head-groups. Such a synthetic strategy offers fine control over adsorption and aggregation, as evidenced by physicochemical characterization of these molecules, uncovering rich phase behavior and diverse biological response. This article covers recent advances in the field of both ‘traditional’ and new azobenzene-containing photosurfactants, and offers directions for future study and use of this unique class of molecule.
The relationship between the geometric features and electronic behavior of CuAln− (n = 11–13) clusters was investigated using the B3LYP method with 6-311+G* basis set. The electronic behaviors were analyzed by using the partial density of states (PDOS). The geometric structures were classified on the basis of the cluster framework and the position of a Cu atom. The Cu atom is added to the surface of the Al framework in Type I. The Cu atom locates at the center or inside of the cluster in the Type II. In addition, the double-wheel type CuAl11− (Type III) was examined. Few d-orbital components of Cu are included in the molecular orbitals (MOs) in the peaks higher than −3.5 eV. The d-orbital of Cu contributes to the MOs in the region lower than −3.5 eV. The sp+d and s-p+d bondings occur in Type I. The s-p+d bonding fundamentally occurs in Type II. The s-p+d bonding of Type II is separated into the bonding and anti-bonding of the d and s-p components with the increasing number of Als. In Type III, the contribution of the d-component of Cu to the orbital hybridization is small.
The structural correlation between the BaO-TiO2-SiO2 (BTS) glass and the corresponding (BTS) glass-ceramic is examined by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) analysis along with Raman spectroscopy and X-ray diffraction (XRD) measurements. From the deconvoluted spectrum of each Si unit, denoted by Qn, in both the BTS glasses and the BTS glass-ceramics, it is found that structural rearrangement of Si occurs from the Q2 and Q3 units to Ba2TiSi2O8 and the residual amorphous region, respectively. These results of 29Si MAS NMR analysis and Raman spectroscopy, together with XRD measurements, show that the local structure of the BTS mother glass reflects that of the corresponding crystals. This finding is expected to be valuable for tailoring the structure of functional glass-ceramics.
Two unresolved issues in molecular self-assembly are discussed. Firstly, a novel method for the investigation of molecular self-assembly processes (QASAP: quantitative analysis of self-assembly process) is introduced and recent progress in the understanding of coordination self-assembly processes revealed by QASAP is described. Secondary, a challenge to the construction of discrete molecular self-assemblies that are formed with the aid of weak, nondirectional molecular interactions (such as van der Waals interactions) and the hydrophobic effect is discussed. In the course of the development of hexameric cube-shaped molecular self-assemblies (nanocubes) from gear-shaped amphiphiles (GSAs) in water, a design principle of hydrophobic surface engineering and a novel strategy for the construction of thermally stable discrete assemblies, molecular ‘Hozo’, are presented.
In this paper, we review the recent research progress on Si pillar assisted hierarchical three dimensional (3D) carbon nanotube structures focusing mainly on the rational modification of the 3D network of single-walled carbon nanotube (3DNC) structures and its potential applications. Compared with conventional carbon nanotube (CNT) based microstructures which have been studied by other researchers, the 3DNC attract more attention because of its unique hierarchical structure which is comprised of interconnected CNTs between Si pillars. Functionalization of CNTs without destroying the hierarchical 3D structure of 3DNC is always a challenge. Physical and chemical vapor depositions, electrochemical depositions, polymer coating, and capillary force induced self-assembly have been applied for the surface modification of 3DNC. Those modified 3DNC structures have been applied to various research areas, like signal enhancement, microfluidic chips, energy storage, catalysis, and sensors, because of their unique hierarchical 3D structures. We also introduce some synthetic works on the capillary force induced wall-shaped CNT structures on pillar substrates.
Water is still mysterious despite intensive and extensive studies over the years. Anomalous behavior of water as a liquid is yet to be fully comprehended. Here we show that the most generally known anomaly of water, the density maximum anomaly, is well accounted for by the formation of nanometer-size ice crystallite at low temperatures. We show spectroscopically that, in cold and super-cooled water, this nanometer-size ice crystallite is formed and coexists with the other two forms of water. Multivariate hyperspectral analysis of 140 temperature dependent Raman spectra in the range of −23∼45 °C determines the three distinct vibrational spectra of the three forms of water and their fractions at different temperatures. Simulation based on the determined fractions successfully reproduces the temperature dependence of density with a maximum at the right temperature. The mystery of the density maximum of water has thus been given an unequivocal solution. The nanometer-size ice crystallite might well be called “nano-ice”.
Flocculation using Fe(II) instead of Fe(III) has been considered more efficient in the removal of As. However, excess Fe(II) used in the process always leaves substantial TFe [Fe(II)+Fe(III)] unutilized. We therefore developed three methods [the one-staged process (OS), the one-staged process with H2O2 (OSH) and the two-staged process (TS)] to remove As(III)/As(V) by Fe(II) (Fe:As = 2.0). Our results indicate that pH is an important factor that determines the utilization efficiency of TFe and the removal efficiency of As. In OS, the initial pH was adjusted before the reaction. At the optimal pHs of 10.0 and 11.0, the removal efficiencies of As(V) and TAs [As(III)+As(V)] could reach 84.0% and 66.7%, with only 61.9% and 80.2% TFe being utilized, respectively. In OSH, H2O2 was added after pH adjustment. After OS, pH was re-adjusted to the optimal values before the next 30 min reaction (TS). Compared with OS, the removal efficiencies of As could increase by more than 9% in OSH and TS at the optimal pHs. Besides, there is more than 10% improvement in the utilization efficiencies of TFe except at 12.0. Accelerating oxidation of Fe(II) or re-adjusting pH is therefore highly efficient for a more efficient removal of As from Fe(II)-rich groundwater.