Optimization and characterization of liposome formulation by mixture design

This study presents the application of the mixture design technique to develop an optimal liposome formulation by using the different lipids in type and percentage (DOPC, POPC and DPPC) in liposome composition. Ten lipid mixtures were generated by the simplex-centroid design technique and liposomes were prepared by the extrusion method. Liposomes were characterized with respect to size, phase transition temperature, ζ-potential, lamellarity, fluidity and efficiency in loading calcein. The results were then applied to estimate the coefficients of mixture design model and to find the optimal lipid composition with improved entrapment efficiency, size, transition temperature, fluidity and ζ-potential of liposomes. The response optimization of experiments was the liposome formulation with DOPC: 46%, POPC: 12% and DPPC: 42%. The optimal liposome formulation had an average diameter of 127.5 nm, a phase-transition temperature of 11.43 °C, a ζ-potential of -7.24 mV, fluidity (1/P)(TMA-DPH)((?)) value of 2.87 and an encapsulation efficiency of 20.24%. The experimental results of characterization of optimal liposome formulation were in good agreement with those predicted by the mixture design technique.     

Acetone Adsorption on Pristine and Pt-doped Graphene: A First-Principles vdW-DF Study

Using van der Waals corrected density functional theory (vdW-DF) method we have investigated the adsorption of acetone molecule on pristine and Pt-doped graphene. Several active sites for both the interacting systems have been considered in the adsorption process including full geometry optimization. We have analyzed the structural and electrical properties of energetically favorable configurations. The results show that adsorption of acetone molecule on the Pt-doped graphene is energetically preferable. The binding energy and bonding distance are determined to be -5.277 eV and 2.206 Å, respectively, accompanying with charge transfer of 1.11 e. Furthermore, the Pt-O bond is rather significantly elongated when acetone is adsorbed on Pt-doped graphene. Compared to pristine graphene, the Pt-doped graphene has stronger interaction with the acetone and may provide more sensitive signal for a single acetone molecule. Meanwhile, practically, the band gap of Pt-doped graphene would become reduced after acetone adsorption. Consequently, our first-principles study presents evidence for a coherent benchmark for the applicability of Pt-doped graphene for acetone adsorption and detection.     

In situ sol–gel fabrication of new poly(amide–ether–imide)/titania (TiO<Subscript>2</Subscript>) nanocomposite thin films containing <Emphasis Type=SmallCaps>l</Emphasis>-leucine moieties

In this study, the synthesis, morphology, and thermal properties of amino acid containing polyimide/titania nanohybrid films are investigated. At first, a chiral diamine containing l-leucine moieties in the structure (synthesized previously) was polymerized with 4,4′-oxydiphthalic anhydride in extremely dry conditions. Resulted poly(amic acid) (PAA) was mixed with a moisture-sensitive titania precursor (tetraethyl orthotitanate [Ti(OEt)₄]) and casted to a dust-free glass plate. The water derived from thermal imidization of PAA hydrolyzed Ti(OEt)₄ to titania nanoparticles with almost spherical shapes. The thermogravimetric analysis of various nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. The transmission electron microscopy of nanohybrid films with 3%, 5%, and 10% w/w of titania contents confirms well dispersion of nanoparticles in the polymer ground. The X-ray diffraction spectra showed that the titania contents have amorphous structure.     

Rank annihilation factor analysis method for spectrophotometric study of second-order reaction kinetics

In this study several methods are described to determine the rate constant of a second-order reaction in the form of A+B→C. These approaches allow circumventing a rank deficiency inherent of a second-order reaction when the spectroscopic data is influenced by additional source of variance. Classically, to determine the unknown rate constant in this kind of systems, one needs to have extra knowledge about the system, including the spectra of the reactants or product and the exact kinetics. In the case of the presence of an unknown phenomenon in the data set that cannot be explained by the model, such as baseline drift, the estimated rate constant might be erroneous. Present work is a modification of the rank annihilation factor analysis (RAFA) algorithm by inclusion of I) pure spectra of reactants, or IIA) mean centering step, or IIB) mean spectrum. The proposed methods can interestingly be applied on a single kinetic run. The performances of the new methods have been evaluated by applying them to analysis of simulated and experimental data.     

Ab initio and DFT studies on 1-(thionitrosomethylene) hydrazine: conformers, energies, and intramolecular hydrogen-bond strength

In the current study, we present an intramolecular HB, molecular structure, π-electrons delocalization and vibrational frequencies analysis of 25 possible conformers of 1-(thionitrosomethylene) hydrazine by means of DFT (B3LYP), MP2 methods in conjunction with the 6-311++G** and augmented correlation-consistent polarized-valence triple-zeta basis sets and G2MP2 theoretical level. The influence of the solvent on the stability order of conformers and the strength of intramolecular hydrogen-bonding was considered using the Tomasi’s polarized continuum model. Statistical analyses of quantitative definitions of aromaticity, nucleus independent chemical shift, harmonic oscillator model of aromaticity, aromatic fluctuation index, and the π-electron delocalization parameter (Q) as a geometrical indicator of a local aromaticity, evaluated for this conformers. Further verification of the obtained transition state structures were implemented via intrinsic reaction coordinate (IRC) analysis. Calculations of the ¹H NMR chemical shift at GIAO/B3LYP/6-311++G** levels of theory are also presented. The calculated highest occupied molecular orbital (MO) and lowest unoccupied MO energies show that charge transfer occur within the molecule. Hydrogen-bond energies for H-bonded conformers were obtained from Espinosa method and the natural bond orbital theory and the atoms in molecules theory were also applied to get a more precise insight into the nature of such H-bond interactions.     

A molecular modeling study on full-length insulin: insight into initial events of amyloid formation

Studies on the structure and physico-chemical properties of amyloid fibrils are important with regard to a better understanding of amyloid diseases such as Alzheimer’s. Insulin is used as a protein model which is easily driven toward amyloid formation. In the present study, five sets of 15 ns molecular dynamics simulations were performed on insulin in order to observe the initial structural changes that occur in the process of amyloid formation. Potential energy, RMSD, and secondary structure percentage of sampled structures were analyzed in all experiments. Common residues that undergo the first conformational changes were detected to be S9 and V10 of the A chain, as well as G8 and S9 of the B chain. The RMSD of truncated insulin increased much more than full-length insulin to about 18 Å. However, the beta-sheet structures percentage of full-length insulin, which is an indicative of amyloid formation, was higher than the truncated form in the presence of salt. This is indicative of the importance of the five residues of the B chain C-terminal in the insulin misfolding process. Overall, simulating full-length insulin under high temperature and in the presence of KCl could be used to assess amyloid formation and potential amyloid inhibitors of this protein.     

Green synthesis of amorphous calcium phosphate nanopowders using Aloe Vera plant extract and assessment of their cytotoxicity and antimicrobial activities

Journal of Sol-Gel Science and Technology - Considering the existing various sources that can supply the nano-biomaterials that are related to the Amorphous Calcium Phosphate (ACP) family, Aloe...     

Synthesis,Crystal Structure,Spectroscopic, Electrochemical and Antimicrobial Properties of Cu(II) Complex with the Mixed Ligands of 2,9‐Dimethyl‐1,10‐phenanthroline and 4‐Hydroxypyridine‐2,6‐dicarboxylic Acid

A mononuclear Cu(II) complex with mixed ligands, formulated as [Cu(hypydc)(dmp)]·H₂O (hypydc=4‐hydroxypyridine‐2,6‐dicarboxylate, dmp=2,9‐dimethyl‐1,10‐phenanthroline), was synthesized and well characterized by single crystal X‐ray diffraction analysis, as well as spectroscopic (IR, UV‐Vis), and electrochemical methods. The Cu(II) atom exhibits a distorted square‐pyramidal geometry. Intermolecular O? H···O and C? H···O hydrogen bonds, π‐π stacking interactions and C? H···π interactions seem to be effective in the stabilization of the crystal structure. The complex was also evaluated for its antimicrobial activity using in vitro microdilution methods. Six standard bacteria and a strain of Candida albicans were used for the antimicrobial activities. There was a very strong activity against Candida albicans and significant activities against Enterococcus fecalis, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, indicating important biological activities of the complex.     

Aptamer-based sensor for diclofenac quantification using carbon nanotubes and graphene oxide decorated with magnetic nanomaterials

In this contribution, a novel label-free electrochemical biosensor for diclofenac (DCF) detection was developed using the unique properties of acid-oxidized carbon nanotubes (CNT), graphene oxide (GO), and Fe₃O₄ magnetic nanomaterials. The GO sheets and CNT were interlinked by ultrafine Fe₃O₄ nanoparticles forming three-dimensional (3D) architectures. The characterization of the nanocomposite was studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), and wavelength-dispersive X-ray (WDX) spectroscopy. Initially, aminated detection probe (aptamer) was surface-confined on the CNT/GO/Fe₃O₄ nanocomposite via the covalent amide bonds formed by the carboxyl groups on the CNT/GO and the amino groups on the oligonucleotides at the 5′ end. Our constructed folding-based electrochemical sensor was used for detection of target molecule utilizing structure-switching aptamers. Signaling arose from changes in electron transfer efficiency upon target-induced changes in the conformation of the aptamer probe. These changes were readily monitored using differential pulse voltammetry technique. This sensor exhibited binding affinities ranging from 100 to 1300 pM with a low detection limit of 33 pM.     

Crystal growth of thin [Zn<Subscript>2</Subscript>(H<Subscript>2</Subscript>N-BDC)<Subscript>2</Subscript>(4-bpdb)] · 3DMF metal–organic framework nanostructure on functionalized surfaces: study of structure effect on methyldopa adsorption affinity

Thin films of a three-dimensional porous Zn(II)-based metal–organic framework, [Zn₂(NH₂-BDC)₂(4-bpdb)] · 3DMF (TMU-17-NH₂), containing azine-functionalized pores, were deposited on surfaces of silk fiber via a stepwise manner. The effect of sequential dipping steps in growth of TMU-17-NH₂ has been studied. These systems depicted a decrease in the size accompanying a decrease in the sequential dipping steps. The TMU-17-NH₂ has been used as matrices for the adsorption and in vitro guest delivery of methyldopa (MD).