In vitro evaluation of the effects of various additives and polymers on nerve growth factor microspheres

Objective: To evaluate the effects of various additives or polymers on the in vitro characteristics of nerve growth factor (NGF) microspheres.

Materials and methods: NGF microspheres were fabricated using polyethylene glycol (PEG), ovalbumin (OVA), bovine serum albumin (BSA) or glucose as protein protectors, and poly(lactide-co-glycolide) (PLGA) or poly(lactic acid) (PLA)/PLGA blends as encapsulation materials.

Results: Encapsulation efficiencies of the NGF microspheres with various additives or polymers were not more than 30%. A comparative study revealed that OVA was somewhat superior over others, and was thus chosen as the protective additive in subsequent experiments. Polymer analysis showed that NGF release from 1:1 PLA (η?=?0.8):PLGA (75/25, η?=?0.45) microspheres lasted for 90?d with a burst release rate of 12.7%. About 40% of the original bioactivity was retained on the 28th day, while 10% was left on the 90th day.

Discussion and conclusion: The combination of OVA as an additive and the PLA/PLGA blend as the coating matrix is suitable for encapsulation of NGF in microspheres for extended release.     

Impact of surfactant selection on the formulation and characterization of microparticles for pulmonary drug delivery

The effect of suspension stabilizers, internal aqueous phase volume and polymer amount were investigated for the production of protein loaded poly(d,l?lactide-co-glycolide) (PLGA) microparticles suitable for pulmonary drug delivery. PLGA microparticles were produced adopting water-in-oil-in-water (W/O/W) solvent evaporation technique and were investigated for surface morphology, particle size, encapsulation efficiency (EE%) and in-vitro release profile. Porous surface morphologies with a narrow size distribution were observed when employing 0.5?ml internal aqueous phase; 23.04?µm (±0.98), 15.05?µm (±0.27) and 22.89?µm (±0.41) for PVA, Tween 80 and oleic acid. Porous microparticles exhibited increased size and reduction in EE% with increasing internal aqueous phase, with non-porous microparticles produced when adopting 2.0?ml internal aqueous phase. The selection of stabilizer influences the size of the pores formed thus offers potential for the aerodynamic properties of the microparticles to be manipulated to achieve suitable aerosolization characteristics for pulmonary delivery of proteins.     

Cu2S nanostructures prepared by Cu-cysteine precursor templated route

A facile Cu-cysteine precursor templated route for the synthesis of Cu₂S nanowires, dendritic-like and flowerlike nanostructures is reported. The Cu-cysteine precursors are prepared through the reaction between Cu²⁺, l-cysteine and ethanolamine at room temperature, and the morphologies of Cu-cysteine precursors can be controlled by adjusting the molar ratio of l-cysteine to Cu²⁺. The Cu-cysteine precursors are used as both templates and source materials for the subsequent preparation of polycrystalline Cu₂S nanostructures by thermal treatment, and the morphologies of the precursors can be well preserved after the thermal transformation to Cu₂S nanostructures. The samples are characterized using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy.     

L-Aspartic acid/L-cysteine/gold nanoparticle modified microelectrode for simultaneous detection of copper and lead

This paper presents an electrochemical microsensor for simultaneous detection of copper (II) and lead (II) using an l-aspartic acid/l-cysteine/gold nanoparticle modified microelectrode. The microelectrode was fabricated by Micro Electro-Mechanical System technique. The complex of gold nanoparticles (AuNPs) and amino acid with carboxyl group was used as the selective ligand for metal ions. The microelectrode was firstly modified with AuNPs to increase the sensitive area of the working electrode. Subsequently, the AuNPs/gold electrode was modified with l-cysteine and then covalently linked with a monolayer of l-aspartic acid using glutaraldehyde. Electrochemical analysis of metal ions was achieved by using square wave voltammetry without stirring. The microsensor exhibited an excellent linear range from 5 μg L^− 1 to 2000 μg L^− 1 with the limit of detection of 1 μg L^− 1. This metal ion detection method based on l-aspartic acid/l-cysteine/gold nanoparticle modified microelectrode is simple, sensitive and it could be used for electrochemical analysis of copper (II) and lead (II).     

Comment on the paper by J. Thomas Joseph Prakash, S. Kumararaman, “Growth and characterization of l-asparagine thiourea monohydrate (LATM): A nonlinear optical single crystal”, Materials Letters 62(2008) 4003-4005

It is argued that the conclusion of the authors of the title paper on obtaining of a new crystal l-asparagine thiourea monohydrate is erroneous. The authors actually have obtained well known l-asparagine monohydrate crystal.     

Facile, one-step controlled synthesis of Se nanocrystals in the presence of l-tyrosine

Se with different morphologies was synthesized using l-tyrosine as reducing agent and soft template by means of hydrothermal method. The method was simple and convenient to handle. The reaction process was monitored using ultraviolet-visible spectroscopy (UV-vis) and Fourier-transform infrared spectroscopy (FTIR). The morphology and crystalline phase were determined by transmission electron microscopy (TEM), scanning electronic microscopy (SEM) and X-ray diffraction (XRD) pattern. The results show that the morphologies and the crystalline phases of Se can be easily controlled. By varying the concentration ratio of l-tyrosine to selenious acid, the morphologies and crystalline phases of Se were not changed, but the diameter of Se was different. Se nano-rods are obtained in the lower temperature, and there is a transformation of microspheres into nanorods of Se with the increase of reaction time or reaction temperature. In addition, we discuss the possible mechanism of the reduction of SeO₃²⁻ ions by l-tyrosine. The eco-friendly, biogenic synthesis strategy could be widely used for preparing inorganic/organic biocomposites.     

A Multi-Criteria Decision Analysis Technique for Stochastic Task Criticality in Project Management

Inherent in project management is the risk that a project fails to meet planned completion deadlines due to delays experienced in individual tasks. As such, certain critical tasks may be candidates for risk management (e.g., the allocation of additional resources such as labor, materials, and equipment) to prevent delays. A common means to identify such critical tasks is with the critical path method (CPM), which identifies a path of tasks in a project network that, when delayed, result in project delays. This work offers a complementary, stochastic approach to CPM that ranks tasks according to their effect on the project completion time distribution, when the distributions of task completion time are delayed. The new hybrid approach is based on the use of a Monte Carlo simulation and a multi-criteria decision analysis technique. Monte Carlo simulation allows for approximating the cumulative distribution function of the total duration of the project, while the multi-criteria decision analysis technique is used to compare and rank the tasks across percentiles of the resulting project completion time distributions. Doing so allows for different percentile weighting schemes to represent decision maker risk preferences. The suggested approach is applied to two project network examples. The examples illustrate that the proposed approach highlights some tasks as risky, which may not always lie on the critical path as identified by CPM. This is valuable for practicing managers as it allows them to properly consider their risk preferences when determining task criticality based on the distribution of project completion time (e.g., emphasizing median vs. upper tail completion time).     

Concentration dependence of solution crystallization for poly(l-lactide) in p-xylene

The macromolecular chain conformation in solution changes with the solvent and temperature, which will affect the formation of crystalline structure in the subsequent crystallization process. The crystallization behavior of poly(l-lactide) samples prepared from solutions with various concentrations was studied by differential scanning calorimetric and X-ray diffraction. It is found that the sample recovered from a dilute solution exhibits higher crystallinity, higher non-isothermal crystallization temperature and faster crystallization rate. The condensation process of polymer chain in dilute solutions has an influence on the crystallization of polymer in the solid state. This results in the acceleration of the melt crystallization rate and the rise of non-isothermal crystallization temperature of PLLA recovered from the dilute solution.     

In vitro bioactivity of chitosan/poly (d,l-lactide-co-glycolide) composites

Porous composites scaffolds of chitosan/poly(d,l-lactide-co-glycolide) were fabricated for tissue engineering applications by thermally induced phase separation and lyophilization techniques. The in vitro bioactivity evaluation of the scaffolds was carried out by analyzing the apatite layers produced on them using SBF as incubation medium. The apatite formation was analyzed using FTIR spectroscopy and Field emission scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The cumulative results obtained from the IR spectra and SEM-EDS suggest that the developed composites might have potential applications in tissue engineering.     

Interlocked chitosan/poly(dl-lactide) blends

A novel processing method was developed to prepare chitosan/poly(dl-lactide) blends. These blends were further examined for their structures. SEM micrographs exhibited that under optimized processing conditions and with appropriate composition proportions, the resulting blends could possess interlocked internal microstructures. The results obtained from TGA and DMA measurements complementarily confirmed that two components could be well blended into a solid construct at a partially miscible level. The main mechanical properties of the blends were also investigated in both dry and hydrated states.     

A C++ object-oriented toolkit for track finding with k-dimensional hits

A library is described for the recognition of tracks in a set of hits. The hits are assumed to be k-dimensional points (k-d), with k≥1, of which a subset can be grouped into tracks by using short-range correlations. A connection graph between the hits is created by sorting the hits first in k-d space using one of the developed, fast, k-space containers. The track-finding algorithm considers any connection between two hits as a possible track seed and grows these seeds into longer track segments using a modified depth-first search of the connection graph. All hit-acceptance decisions are called via abstract methods of an acceptance criterion class which isolates the library from the application's hit and track model. An application is tuned for a particular tracking environment by creating a concrete implementation for the hit and track acceptance calculations. The implementer is free to trade tracking time for acceptance complexity (influencing efficiency) depending on the requirements of the particular application. Results for simulated data show that the track finding is both efficient and fast even for high noise environments.     

Facile and controllable one-step fabrication of selenium nanoparticles assisted by l-cysteine

A simple and solution-phase approach for large-scale synthesis of selenium nanoparticles (Nano-Se) by reducing sodium selenite (Na₂SeO₃) with l-cysteine has been demonstrated in this study. l-cysteine was used as both the reducing agent and surface modifier to control the formation of Nano-Se. The effects of reactant concentrations and ratios, and reaction time on the size and stability of Nano-Se were also investigated. The morphology and chemical composition of Nano-Se were characterized using various spectroscopic and microscopic methods. The results showed that varying the concentration ratio of l-cysteine to Na₂SeO₃ could control the diameter and morphology of Nano-Se, but not affecting their crystalline phases and chemical compositions. Monodisperse and homogeneous spherical Nano-Se with an average diameter of about 100 nm could be synthesized with the concentration ratio of l-cysteine to Na₂SeO₃ at 4:1. A striking feature of the as-synthesized Nano-Se was their good stability when dispersed in the reaction solutions, which indicates their potential in medical applications.     

Investigating thermal degradation, crystallization and surface behavior of l-lactide, glycolide and trimethylene carbonate terpolymers used for medical applications

In this paper, the crystallization temperature (T_C), the melting temperature (T_m), the degradation mechanism and the surface properties of copolymers based on l-lactide, glycolide and trimethylene carbonate copolymers are investigated. The copolymers containing only l-lactide and trimethylene carbonate showed an endotherm peak in the DSC. Those containing three monomers (i. e. terpolymer) did not exhibit melting which may, otherwise, indicate the formation of an amorphous structure. The kinetic studies of thermal degradation in two different atmospheres using the FWO method revealed that single step degradation exists and the type of atmosphere (N₂ or O₂₎ has no influence on the degradation for these copolymers. The surface properties of the system showed that for the terpolymer containing trimethylene carbonate the contact angle of DDI water droplet on the polymer surface becomes smaller than that without TMC, vindicating inherent softness and stronger hydrophilic structure in the terpolymer.     

Synthesis, spectral and thermal studies of new nonlinear optical crystal: l-valinium fumarate

An organic nonlinear optical material, l-valinium fumarate (abbreviated as LVF) has been successfully synthesized and good quality single crystals have been grown by low temperature solution growth method. The purified form of LVF is achieved by repeated crystallization. The cell parameters of LVF have been determined using single crystal X-ray diffraction technique and the crystal system is found as monoclinic. From the UV-Vis-NIR absorption spectrum, the good transparency is revealed from 300 nm to 1100 nm. The mode of vibration of different molecular groups present in LVF was identified by FT-IR spectral analysis. The thermogravimetric (TGA) and differential thermal analysis (DTA) studies show the thermal behavior and crystal was thermally stable up to 266 °C. Second harmonic generation (SHG) conversion test was made to explore the nonlinear optical behavior of this material using Kurtz and Perry method.     

Al2O3/含铈中锰钢界面CeAlO3生长动力学

本文在理论分析和界面结构研究的基础上,在Al₂O₃/含铈中锰钢系建立了界面反应产物CeAlO₃层的生长模型,得出CeAlO₃层厚度S与时间t的关系遵循抛物线规律。实验结果与理论模型和规律相一致。      

Self-assembly of silver nanoparticles into dendritic flowers from aqueous solution

Similar to folding of proteins into three-dimensional (3D) structure, self-assembly of metallic nanoparticles (NPs) into dendritic or other supramolecular structures is of greater interest, yet less understood. We observed spontaneous, template-free organisation of silver NPs into 3D, dendritic, elegant, flower-like structures from an aqueous solution containing AgNO₃ and L-cysteine (Cys). The resultant NPs and dendritic structures were characterised using UV–Vis spectroscopy and scanning and transmission electron microscopy. The process initiated most likely by diffusion-limited aggregation in the liquid phase, which were further grown into elegant, dendritic flowers probably by evaporation of residual wetting layer of larger NPs. Electrostatic attraction between –COO^? and –NH₃ ⁺ groups of L-Cys on the surface of silver NPs may also have a role in their growth.     

Formulation and characterization of ethylcellulose microparticles containing .l-alanyl- l-glutamine peptide

Context: The l-alanyl-l-glutamine peptide (AGP) has been effective to promote acute glycemia recovery during long-term insulin-induced hypoglycemia (IIH), and the oral administration of AGP is suggested to prevent prolonged hypoglycemia, such as nocturnal hypoglycemia.

Objective: Considering the ability of AGP on glycemia recovery and AGP’s fast metabolism, the aim of current study was to obtain and characterize ethylcellulose microparticles to deliver the drug for a prolonged time.

Materials and Methods: Microparticles were prepared by simple and double emulsification/hardening method and characterized by scanning electron microscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) and FT-Raman spectroscopy and in vitro release.

Results and Discussion: Spherical structures with a mean diameter between 9.30?µm and 13.19?µm were formed. TG analysis showed that the thermal stability of AGP was even more increased by encapsulation with ethylcellulose. In addition, TG, DSC, FTIR and FT-Raman analyses proved that AGP was encapsulated in a molecular way. Higher values of encapsulation efficiency were observed for the microparticles prepared by double emulsification (57.83–83.67%) than for those prepared by simple emulsification (18.37%). However, the last ones could release the peptide in a quicker and more extensive manner than those prepared by double emulsification.

Conclusion: For the first time, microparticles containing AGP were developed and exhibited prolonged in vitro release as well as protection to the drug, and it could be considered as a dosage form for patients who suffer from insulin-induced hypoglycemia and/or nocturnal hypoglycemia.     

Ellipsometric determination of optical properties of carbazole-containing poly(l-glutamate) thin films prepared from different solvents

In this study, the refractive indices (n) and thicknesses of carbazole-containing hole-transport materials such as poly(γ-carbazolylethyl l-glutamate) (PCELG) and poly(N-vinyl carbazole) (PVCz) films were determined by carrying out ellipsometric measurements. The thicknesses of PCELG and PVCz films determined by ellipsometric analysis were in good agreement with those determined by surface profilometry. The dependence of the refractive indices of the PCELG films on film thickness was classified into two types on the basis of the solvent from which the films were prepared: the refractive indices either increased with increasing film thickness, as in the case of PCELG films prepared from 1,2-dichloroethane (DCE) and monochlorobenzene (?-Cl), or were independent of the film thickness, as in the case of films prepared from 1,1,2,2-tetrachloroethane (TCE). A comparison of these results with the structures of the polymers, as determined by ¹H NMR, reveals that the two types of dependences of the refractive indices of the PCELG thin film on the film thickness can be attributed to the two types of aggregation structures and/or orientational characteristics corresponding to the helical conformation of the polymer. In contrast, the refractive indices of PVCz films are governed mainly by the film thickness. Finally, we would like to emphasize that the combination of ellipsometry and other techniques such as NMR and surface profilometry provide information not only on the film thickness and refractive index but also on the aggregation structure in thin films with thicknesses on the order of 50 nm.     

Vapor pressures of Y, Ba, Cu precursors for the growth of YBa2Cu3O7 by MOVPE

The vapor pressures of the-diketonates Y(THD), Ba(THD), and Cu(THD), commonly used as precursors for MOVPE of YBa₂Cu₃O₇, and Y(MCP) were measured at different temperatures. A time-resolved static method recording the pressure vs. time at constant temperature was used, permitting us to deduce the vapor pressure even if the materials tend to decompose. The values of the constants of the Clausius-Clapeyron equation log₁₀p(T)/p ₀=A-B/T are,A=11.7, 8.7, 8.27, 16.6 andB=4359, 2654, 3602, and 6453 K for Y(THD), Y(MCP), Ba(THD), and Cu(THD), respectively withp ₀= 1 Pa and temperatureT in K. The thermal stability of the sources was measured and are discussed.