On-Surface Self-Assembled Structural Transformation Induced by Schiff Base Reaction and Hydrogen bonds.

By utilizing scanning tunneling microscopy (STM), the self-assembled nanostructures of three characteristic aldehydes have been examined at the solution-solid interface. By introducing the active reactant 5-aminoisophthalic acid (5-AIPA), we succeeded in changing the self-assembled molecular structures through the condensation reaction and obtained the information on structural transformation in real time. The corresponding carboxyl conjugated derivatives were formed in situ and developed into the closely packed and ordered molecular architectures via hydrogen bonds at the solution-solid surface. The relevant simulations have been utilized to interpret the mechanisms of forming the nanostructures. The corresponding theoretical calculation is used to explain the reaction mechanism. Compared with the traditional ways, the on-surface condensation reaction in situ could not only provide a more convenient method for regulating the self-assembled architectures but also offer a promising strategy for building functional nanostructures and devices.

[Intensity loss of two-photon excitation fluorescence microscopy images of mouse oocyte chromosomes].

As an optical microscope with high resolution, two-photon excitation (TPE) fluorescence microscope is widely used in noninvasive 3D optical imaging of biological samples. Compared with confocal laser scanning microscope, TPE fluorescence microscope provides a deeper detecting depth. In spite of that, the image quality of sample always declines as the detecting depth increases when a noninvasive 3D optical imaging of thicker samples is performed. Mouse oocytes with a large diameter, which play an important role in clinical and biological fields, have obvious absorption and scattering effects. In the present paper, we performed compensation for two-photon fluorescence images of mouse oocyte chromosomes. Using volume as a parameter, the attenuation degree of these chromosomes was also studied. The result of our data suggested that there exists a severe axial intensity loss in two-photon microscopic images of mouse oocytes due to the absorption and scattering effects. It is necessary to make compensation for these images of mouse oocyte chromosomes obtained from two-photon microscopic system. It will be specially needed in studying the quantitative three-dimensional information of mouse oocytes.

[Synthesis, characterization and luminescence properties of coordination compounds of rare earth with p-tert-butyl-calix[8] arene].

Fourteen solid coordination compounds of rare earth(Sm3+, Eu3+, Tb3+ and Dy3+ and Ln3+ (La3+, Gd3+ and Y3+)-doped Tb3+ with p-tert-butyl-calix[8] arene (LH8) have been synthesized and characterized. Elemental analysis, rare erth complexometry, 1H NMR spectra and TG-DTA have been studied. The results suggest that the complexes have the composition of [RE2 (LH2)(DMSO)5]DMSO, [RE2 (LH2) (DMF)5] 2DMF, [LnTb (LH2) (DMSO)5] DMSO and [LnTb (LH2) (DMF)5] 2DMF respectively. Fluorescence spectrum suggests that the Tb3+ complexes have characteristic luminescence, and its fluorescence intensity is enhanced after doping with La3+, Gd3+ and Y3+. The influence of the doping ions and two neutral ligands (DMSO and DMF) has also been discussed. In addition, the fluorescence lifetime of some complexes has been investigated.

Understanding agglomeration of indomethacin during the dissolution of micronised indomethacin mixtures through dissolution and de-agglomeration modeling approaches.

The purpose of this research was to correlate the state of agglomeration determined by the modeling of dissolution and de-agglomeration profiles, using mixtures of micronised indomethacin designed to have different dissolution rates and extents of particle agglomeration in dissolution media. Dissolution profiles were determined using the USP paddle method. De-agglomeration profiles were obtained from laser diffraction particle sizing of mixtures of indomethacin in dissolution media under non-sink conditions. Data were modeled and key parameters estimated using a non-linear least squares estimation algorithm. The key parameters of initial apparent volume concentrations as dispersed and agglomerated particles, and dissolution rate constants (for dissolution modeling), and the apparent volume concentrations of dispersible and non-dispersible agglomerates and the de-agglomeration rate constant (for de-agglomeration modeling) were related to indomethacin and sodium lauryl sulphate concentrations in the lactose-povidone mixtures. Micronised sodium lauryl sulphate added to the mixture was more effective in de-agglomeration than equivalent concentrations in the dissolution media. An excellent correlation existed between the total initial apparent volume concentration of agglomerates determined by dissolution and de-agglomeration (P=0.98). The use of key parameters estimated from the modeling of dissolution and de-agglomeration profiles provides a useful tool in dosage form development of formulations of poorly water soluble drugs.

Modeling the deagglomeration of micronized benzodiazepines from powder mixtures added to dissolution media.

The objective of this research was to model benzodiazepine deagglomeration profiles of percent agglomerated versus time when interactive mixtures containing micronized benzodiazepines were added to water. Micronized diazepam, nitrazepam, oxazepam, and, for ternary mixtures, micronized sodium lauryl sulfate were mixed with lactose-povidone granules (250-355 microm). After rapid dissolution of the lactose granules, bimodal particle size distributions of benzodiazepines, determined by laser diffraction particle sizing, represented dispersed and agglomerated distributions. The concentrations of agglomerated particle decreased with time and approached constant values. Deagglomeration profiles were determined and best modeled by a three-parameter single-exponential decay equation. A nonlinear least-squares approach was used to estimate the concentration of dispersible (C(0)) and nondispersible agglomerates (C(0a)) and the deagglomeration rate constant (K(a)). Increasing benzodiazepine and sodium lauryl sulphate concentrations in the lactose-povidone mixtures increased both dispersible and nondispersible agglomerate concentrations. Deagglomeration rate was relatively fast with half-lives around 15 min. The estimated parameters of C(0a) and K(a) may provide useful information in optimizing the design of formulations of poorly water soluble, micronized drugs to maximize their dispersion.

De-agglomeration of micronized benzodiazepines in dissolution media measured by laser diffraction particle sizing.

The objective of this research was to develop a method to characterize the degree of particle agglomeration using laser diffraction particle sizing, following the addition of benzodiazepine interactive mixtures to water. Interactive mixtures of diazepam, nitrazepam and oxazepam (up to 20% w/w) were prepared by mixing micronized benzodiazepines with lactose granules (250-355 microm). Micronized sodium lauryl sulfate and cetrimide (up to 5% w/w) were added to the benzodiazepine-lactose interactive mixes to produce ternary mixtures. Particle size distributions of benzodiazepines, after addition of the interactive mixtures to water, were determined using laser diffraction particle sizing. Bimodal distributions representing dispersed particles and agglomerates were observed initially after lactose carrier dissolution. Partial agglomerate to dispersed particle transition occurred during a 60-min observation period for all mixtures, reaching a constant level of agglomeration after this time. Interactive mixtures with higher benzodiazepine concentrations displayed transition profiles with higher levels of agglomeration. The presence of surfactant in interactive mixtures dramatically decreased agglomeration. Sodium lauryl sulfate was more effective than cetrimide in dispersing agglomerates. The shape of the transition curves during de-agglomeration demonstrated the presence of stable agglomerates that remained after the initial transition; these may be important in explaining dissolution and absorption rates.

[Synthesis and characterization of Eu (La) complexes with benzoate and alpha,alpha'-dipyridyl].

A series of dinuclear complexes of different molar ratio of Eu3+ to La3+ with benzoate and alpha,alpha'-dipyridyl have been synthesized in the anhydrous alcohol. Their composition was RE(Dipy)L3.H2O (RE = Eu3+ and La3+, L = C6H5COO-). Their UV spectra and IR spectra were studied. The UV absorption spectral peaks of benzoic acid and alpha,alpha'-dypyridyl shifted 2-9 nm in the complexes. The characteristic anti-symmetric and symmetric stretching vibrations of carboxylate group shifted to lower frequency, while the C=N stretching vibrations shifted to higher frequency in the complexes. These situations show that chemical bonds have formed between the ligands and the rare earth ions. The fluorescence spectra of the complexes were investigated, and the results indicate that the fluorescence emission intensity of europium ion was sensitized by lanthanum ion in the complexes. These facts show that not only the ligands but also the lanthanum complex can transfer the absorbed energy to Eu3+ ion in the complexes.

[Preparation and properties of complex of europium lanthanum with crown ether and p-phthalic acid].

Two complexes of crown ether europium (EuL) and crown ether lanthanum (LaL) were synthesized by europium perchlorate and lanthanum perchlorate with 18-crown-6(18-C-6) respectively. The heternuclear complexes of europium-lanthanum p-phthalic acid crown ether were prepared by the two complexes (EuL and LaL) with p-phthalic acid. The elemental analysis shows that its composition is EuLaL2L'(ClO4)4.6H2O(L = 18-C-6 and L' = p-C6H4 (COO)2). The IR spectra, UV-spectra and molar conductor indicate that both ligands (L and L') coordinate rare earth ions (Eu3+ and La3+), but perchlorate group is free. The fluorescence spectra show that the fluorescence intensities of the complex of heternuclear (EuLaL2L'(ClO4)4.6H2O) are more than eight times that of the crown ether europium complex. It was shown that the linked ligand (p-phthalic acid) can transfer the absorbed energy of Lanthanum-crown ether to europium-crown ether with high efficiency.