Preparation of chitosan nanoparticles by TPP ionic gelation combined with spray drying,and the antibacterial activity of chitosan nanoparticles and a chitosan nanoparticle–amoxicillin complex

Chitosan nanoparticles were prepared from chitosan with various molecular weights by tripolyphosphate (TPP) ionic gelation combined with a spray drying method. The morphologies and characteristics of chitosan nanoparticles were determined by TEM, FE-SEM and from their mean sizes and zeta potentials. The effect of chitosan molecular weight (130, 276, 760 and 1200 cPs) and size of spray dryer nozzle (4.0, 5.5 and 7.0 µm) on mean size, size distribution and zeta potential values of chitosan nanoparticles was investigated. The results showed that the mean size of chitosan nanoparticles was in the range of 166–1230 nm and the zeta potential value ranged from 34.9 to 59 mV, depending on the molecular weight of chitosan and size of the spray dryer nozzles. The lower the molecular weight of chitosan, the smaller the size of the chitosan nanoparticles and the higher the zeta potential. A test for the antibacterial activity of chitosan nanoparticles (only) and a chitosan nanoparticle–amoxicillin complex against Streptococcus pneumoniae was also conducted. The results indicated that a smaller chitosan nanoparticle and higher zeta potential showed higher antibacterial activity. The chitosan nanoparticle–amoxicillin complex resulted in improved antibacterial activity as compared to amoxicillin and chitosan nanopaticles alone. Using a chitosan nanoparticle–amoxicillin complex could reduce by three times the dosage of amoxicillin while still completely inhibiting S. pneumoniae.     

The Application of High Surface Area Cordierite Synthesized from Kaolin as a Substrate for Auto Exhaust Catalysts

Cordierite is often used as substrate for three way catalysts for the treatment of automobile exhaust gases, mainly because of its high stability. In this paper, different synthesis methods of cordierite are systematically investigated with the aim to improve functionalities and surface properties. Amongst them, the conventional sintering method from kaolin was paid attention to, due to economic reasons and the high yield of obtained cordierite phase. With the aim to improve the porosity, burnable additives were added to the precursor powder and acid leaching was applied to treat the surface of the substrates. The latter was found to be the most efficient method, especially when dolomite and industrial aluminum hydroxide were added in the precursors. Surface area of the cordierite sample reaches 139 m²/g with acceptable mechanical strength. The increase of the cordierite surface area resulted in a higher loading of MnO₂‐Co₃O₄‐NiO catalytic active phases, leading to higher activity for the complete oxidation of CO. The deposition of an additional ψ‐Al₂O₃ support layer, which is normally done for these kinds of applications, becomes superfluous.     

Bonding and singlet–triplet gap of silicon trimer: Effects of protonation and attachment of alkali metal cations

We revisit the singlet–triplet energy gap (ΔE_ST) of silicon trimer and evaluate the gaps of its derivatives by attachment of a cation (H⁺, Li⁺, Na⁺, and K⁺) using the wavefunction‐based methods including the composite G4, coupled‐cluster theory CCSD(T)/CBS, CCSDT and CCSDTQ, and CASSCF/CASPT2 (for Si₃) computations. Both ¹A₁ and ³ states of Si₃ are determined to be degenerate. An intersystem crossing between both states appears to be possible at a point having an apex bond angle of around α = 68 ± 2° which is 16 ± 4 kJ/mol above the ground state. The proton, Li⁺ and Na⁺ cations tend to favor the low‐spin state, whereas the K⁺ cation favors the high‐spin state. However, they do not modify significantly the ΔE_ST. The proton affinity of silicon trimer is determined as PA(Si₃) = 830 ± 4 kJ/mol at 298 K. The metal cation affinities are also predicted to be LiCA(Si₃) = 108 ± 8 kJ/mol, NaCA(Si₃) = 79 ± 8 kJ/mol and KCA(Si₃) = 44 ± 8 kJ/mol. The chemical bonding is probed using the electron localization function, and ring current analyses show that the singlet three‐membered ring Si₃ is, at most, nonaromatic. Attachment of the proton and Li⁺ cation renders it anti‐aromatic. © 2015 Wiley Periodicals, Inc.     

Dye-sensitized solar cells based on functionalized truxene structure

Three new metal-free organic dyes(TX1, TX2 and TX3) based on truxene core structure, with triphenylamine as the electron donor, thiophene as the p spacers, and cyanoacetic acid or rhodanine-3-acetic acid as the electron acceptor are designed and synthesized. Their UV–vis absorption spectra,electrochemical and photovoltaic properties were investigated. The cyanoacrylic acid is verified to be a better acceptor unit(meanwhile the anchoring group) compared to the rhodanine-3-acetic acid. And also, two anchoring groups in TX2 could provide stronger adsorption ability on the Ti O2 surface. In addition, the EIS results indicate a slower charge recombination processes for TX2. As a result, dye TX2 bearing two cyanoacetic acid outperforms the other two dyes, exhibiting the photo-conversion efficiency of 2.64%, with Jsc= 5.09 m A cm–2, Voc= 729 m V, FF = 71.1.     

Measurement of isomeric yield ratios for the natHo(γ,xn)164m,g;162m,gHo reactions in the bremsstrahlung energy region from 45 to 65 MeV

We have measured the isomeric yield ratios for the ^164m,gHo and the ^162m,gHo isomeric pairs formed via photonuclear reactions ¹⁶⁵Ho(γ,n)^164m,gHo and ¹⁶⁵Ho(γ,3n)^162m,gHo in the bremsstrahlung energy region from 45 to 65 MeV in steps of ?E = 5 MeV by the activation method. The induced γ-activities of the irradiated holmium foils were measured by a coaxial high-purity germanium detector coupled to a PC-based multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made. The experimental results at bremsstrahlung energies of 45, 50, 55, 60, and 65 MeV are 0.408 ± 0.027, 0.413 ± 0.027, 0.427 ± 0.029, 0.452 ± 0.032, and 0.448 ± 0.031 for the ^164m,gHo isomeric pair, and 0.587 ± 0.041, 0.624 ± 0.044, 0.652 ± 0.045, 0.637 ± 0.045, and 0.668 ± 0.046 for the ^162m,gHo isomeric pair, respectively. The present results are the first measurements at bremsstrahlung energies just above the giant dipole resonance region. The obtained results confirm the dependence of isomeric ratios on the incident photon energy as observed in some earlier experiments.     

Expression and Purification of Biologically Active Human FGF2 Containing the b′a′ Domains of Human PDI in Escherichia coli

Among the members of the fibroblast growth factor (FGF) family that affect the growth, differentiation, migration, and survival of many cell types, FGF2 is the most abundant in the central nervous system. Because of its wound healing effects, FGF2 has potential as a therapeutic agent. The protein is also added to the culture media to maintain stem cells. Expression and purification procedures for FGF2 that are highly efficient and low cost have been intensively investigated for the past two decades. Our current study focuses on the purification of FGF2 fused with b′a′ domains of human protein disulfide isomerase to elevate overexpression, solubility, and stability with a simplified experimental procedure using only ion exchange chromatography, as well as on the confirmation of the biological activity of FGF2 on fibroblast Balb/c 3T3 cells and hippocampal neural cells.     

Micro-solid phase extraction of ochratoxin A, and its determination in urine using capillary electrophoresis

We describe a simple, environmentally friendly and selective technique for the determination of ochratoxin A (OTA) in urine. It involves (a) the use of a molecularly imprinted polymer as a sorbent in micro-solid-phase extraction in which the sorbent is contained in a propylene membrane envelope, and (b) separation and detection by capillary electrophoresis (CE). Under optimized conditions, response is linear in the range between 50 and 300 ng mL^?1 (with a correlation coefficient of 0.9989), relative standard deviations range from 4 to 8 %, the detection limit for OTA in urine is 11.2 ng mL^?1 (with a quantification limits of 32.5 ng mL^?1) which is lower than those of previously reported methods for solid-phase extraction combined with CE. The recoveries of OTA from urine spiked at levels of 50, 150 and 300 ng mL^?1 ranged from 93 to 97 %.