Studies on the stability and kinetics of drug release of dexamethasone phosphate intercalated layered double hydroxides nanohybrids

We report the intercalation of dexamethasone sodium phosphate drug in Mg/Al layered double hydroxides (LDHs) through co-precipitation technique. The as-synthesized nanohybrid was characterized by XRD, FTIR and thermal analysis techniques, which reveal that the dexamethasone phosphate anions are accommodated within the brucite layers. The shifting in the stretching frequency of phosphate anion of the drug provides strong evidence that the drugs are bonded to LDHs through electrostatic force. The surface charge analysis suggested the possibility of charge manipulation in LDHs system by varying intercalated anions. In-vitro release study of as-synthesized nanohybrid particles suggests a significant reduction in release rate of dexamethasone phosphate anions from Mg/Al–Dexa LDHs and is due to confinement of drugs in the interlayer. The mechanism of drugs diffusion in nanohybrid is studied by using dissolution–diffusion kinetic model, which reveals that it is probably due to dissolution and intra-particle diffusion of anions in the physiological medium.     

MIXED-CONVECTIVE COOLING OF AN ISOTHERMAL HOT SURFACE BY CONFINED SLOT JET IMPINGEMENT

The flow and heat transfer characteristics in the cooling of a heated surface by impinging slot jets have been investigated numerically. Computations are done for vertically downward-directed two-dimensional slot jets impinging on a hot isothermal surface at the bottom and confined by a parallel adiabatic surface on top. Some computations are also performed where the jet is vertically upward, with an impingement plate at the top. The principal objective of this study is to investigate the associated heat transfer process in the mixed-convective regime. The computed flow patterns and isotherms for various domain aspect ratios (4–10) and for a range of jet exit Reynolds numbers (100–500) and Richardson numbers (0–10) are analyzed to understand the mixed-convection heat transfer phenomena. The local and average Nusselt numbers and skin friction coefficients at the hot surface for various conditions are presented. It is observed that for a given domain aspect ratio and Richardson number, the average Nusselt number at the hot surface increases with increasing jet exit Reynolds number. On the other hand, for a given aspect ratio and Reynolds number, the average Nusselt number does not change significantly with Richardson number, indicating that the buoyancy effects are not very significant in the overall heat transfer process for the range of jet Reynolds number considered in this study. Also, for the same problem configuration, the average Nusselt number does not change significantly when the jet is moving upward or downward.     

Artificial Neural Network Approach to Segregation Characteristic of Binary Heterogeneous Mixtures in Promoted Gas-Solid Fluidized Beds

Binary mixtures of particles of the same size but of different densities are fluidized in a 15 cm diameter column with a perforated plate distributor and two coaxial promoters. In the present work an attempt has been made to study the fluidization and the segregation characteristic of density-variant solids of the same size in terms of segregation distance. The dimensionless segregation distance has been correlated with other dimensionless groups relating to various system parameters: ratio of the density of jetsam particles to that of flotsam, initial static bed height, height of layer of particles above the bottom grid, superficial gas velocity, and average density of the mixture on the basis of the dimensional analysis approach for both un-promoted and promoted beds. Correlations have also been developed with the above system parameters by using an artificial neural network approach for different types of fluidized beds, and the findings with respect to both approaches have been compared with each other. The values of segregation distance for promoted beds have also been compared with those for the un-promoted bed in this work.     

Elastic–plastic adhesive contact of rough surfaces with asymmetric distribution of asperity heights

The elastic–plastic adhesive contact of rough surfaces is extended to include asymmetric distribution of asperity heights using the Weibull distribution with skewness as the key parameter to characterize asymmetry. The well-established elastic adhesion index and plasticity index are used to consider the different conditions that arise as a result of varying load and material parameters. The loading and unloading behaviour for different combinations of adhesion index, plasticity index and skewness values are obtained as functions of mean separation between the surfaces. It is seen that surfaces with negative skewness experience higher adhesion compared to surfaces with positive or zero skewness.     

Templated Synthesis of Gold Nanorods (NRs): The Effects of Cosurfactants and Electrolytes on the Shape and Optical Properties

Seeded growth of gold nanorods (NRs) has been accomplished in a micellar medium containing mixed surfactants or a high salt concentration. Cetyl trimethylamoniumbromide (CTAB) forms micelles upon which the growth of rod shaped gold nanoparticles occurs. AgNO₃ is introduced into the growth solution to enhance the formation of NRs. The roles of non-ionic surfactants such as Tween and Triton, and of electrolytes such as sodium chloride and potassium chloride have been examined. As the concentration of these additives in the growth solution is increased, the aspect ratio of the NRs increases to a critical limit, after which it decreases again. Upon carefully controlling the content of Triton X-100 or Tween 20 in the growth solution, these non-ionic surfactants assisted in fine-tuning the shape of gold NRs (e.g. rectangular or “dogbone”). The growth pattern of the NRs fits into the model of a soft template formed by the mixture of CTAB and non-ionic surfactants.     

Synthesis and characterization of chitosan/cloisite 30B film for controlled release of ofloxacin

In this research program, chitosan film was prepared by blending chitosan with Cloisite 30 B at different concentrations 0 wt %, 1 wt %, and 2.5 wt %. The blends were characterized by Fourier transmission infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X‐ray diffraction (XRD) analysis. From the FTIR spectra the various groups present in chitosan/C 30 B blend were monitored. The homogeneity, morphology, and crystallinity of the blends were ascertained from SEM and XRD data, respectively. The most suitable form of blend was taken and used as a carrier for the controlled release of ofloxacin. The swelling studies have been carried out at different drug loading. Drug release kinetics was analyzed by plotting the cumulative release data versus time by fitting to an exponential equation which indicated the occurrence of non‐Fickian type of kinetics. The drug release was investigated at different pH medium and it was found that the drug release depends upon the pH medium as well as the nature of matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparison study of chitosan,EDTA, eugenol and peppermint oil for antioxidant and antimicrobial potentials in chicken noodles and their effect on colour and oxidative stability at ambient temperature storage

The aim of this study was to investigate the antioxidant and antimicrobial activity of chitosan, EDTA, eugenol and peppermint essential oil and their effect on color and oxidative stability of chicken noodles stored at 35 ± 2 °C. Results indicated that among the four preservatives, eugenol treatment exhibited higher ABTS⁺ (2-2-azinobis-3ethylbenthiazoline-6-sulphonic acid) radical cation activity (89.54%), DPPH (1, 1-diphenyl-2-picrylhydrazil) (51.30%) and superoxide anion scavenging activity (66.82%). Total polyphenol content was also higher in eugenol treated samples. The samples treated with eugenol and chitosan protect against an increase lightness (L-value) and decrease in redness (a) and yellowness (b) values during storage. However, pH value was highest in noodles with chitosan treatment while TBARS (2-thiobarbituric acid reacting substances) and FFA (Free fatty acids) contents were lowest in noodles with eugenol irrespective of storage periods. Eugenol treatment also showed positive impact on microbiological quality and sensory attributes. In conclusion, eugenol has more potential as a natural preservative to increase shelf-life of chicken noodles.     

Composite polymeric magnetic nanoparticles for co-delivery of hydrophobic and hydrophilic anticancer drugs and MRI imaging for cancer therapy

Exercising complementary roles of polymer-coated magnetic nanoparticles for precise drug delivery and image contrast agents has attracted significant attention in biomedical applications. The objective of this study was to prepare and characterize magnetic nanoparticles embedded in polylactide-co-glycolide matrixes (PLGA-MNPs) as a dual drug delivery and imaging system capable of encapsulating both hydrophilic and hydrophobic drugs. PLGA-MNPs were capable of encapsulating both hydrophobic and hydrophilic drugs in a 2:1 ratio. Biocompatibility, cellular uptake, cytotoxicity, membrane potential, and apoptosis were carried out in two different cancer cell lines (MCF-7 and PANC-1). The molecular basis of induction of apoptosis was validated by Western blotting analysis. For targeted delivery of drugs, targeting ligand such as Herceptin was used, and such a conjugated system demonstrated enhanced cellular uptake and an augmented synergistic effect in an in vitro system when compared with native drugs. Magnetic resonance imaging was carried out both in vitro and in vivo to assess the efficacy of PLGA-MNPs as contrast agents. PLGA-MNPs showed a better contrast effect than commercial contrast agents due to higher T(2) relaxivity with a blood circulation half-life ～ 47 min in the rat model. Thus, our results demonstrated the dual usable purpose of formulated PLGA-MNPs toward either, in therapeutics by delivering different hydrophobic or hydrophilic drugs individually or in combination and imaging for cancer therapeutics in the near future.     

Chitosan-functionalized graphene oxide as a nanocarrier for drug and gene delivery

The covalent functionalization of graphene oxide (GO) with chitosan (CS) is successfully accomplished via a facile amidation process. The CS-grafted GO (GO-CS) sheets consist of about 64 wt.% CS, which imparts them with a good aqueous solubility and biocompatibility. Additionally, the physicochemical properties of GO-CS are studied. As a novel nanocarrier, GO-CS is applied to load a water-insoluble anticancer drug, camptothecin (CPT), via π-π stacking and hydrophobic interactions. It is demonstrated that GO-CS possesses a superior loading capacity for CPT, and the GO-CS-CPT complexes show remarkably high cytotoxicity in HepG2 and HeLa cell lines compared to the pure drug. At the same time, GO-CS is also able to condense plasmid DNA into stable, nanosized complexes, and the resulting GO-CS/pDNA nanoparticles exhibit reasonable transfection efficiency in HeLa cells at certain nitrogen/phosphate ratios. Therefore, the GO-CS nanocarrier is able to load and deliver both anticancer drugs and genes.     

Determination of hemin-binding characteristics of proteins by a combinatorial peptide library approach

Studies of the binding of heme/hemin to proteins or peptides have recently intensified as it became evident that heme serves not only as a prosthetic group, but also as a regulator and effector molecule interacting with transmembrane and cytoplasmic proteins. The iron‐ion‐containing heme group can associate with these proteins in different ways, with the amino acids Cys, His, and Tyr allowing individual modes of binding. Strong coordinate‐covalent binding, such as in cytochrome c, is known, and reversible attachment is also discussed. Ligands for both types of binding have been reported independently, though sometimes with different affinities for similar sequences. We applied a combinatorial approach using the library (X)₄(C/H/Y)(X)₄ to characterize peptide ligands with considerable hemin binding capacities. Some of the library‐selected peptides were comparable in terms of hemin association independently of whether or not a cysteine residue was present in the sequence. Indeed, a preference for His‐based (≈39 %) and Tyr‐based (≈40 %) sequences over Cys‐based ones (≈21 %) was detected. The binding affinities for the library‐selected peptides, as determined by UV/Vis spectroscopy, were in the nanomolar range. Moreover, selected representatives efficiently competed for hemin binding with the human BK channel hSlo1, which is known to be regulated by heme through binding to its heme‐binding domain.