The Cyclodextrins as Modelling Agents of Drug Controlled Release

The controlled release of nicardipine (NC) was achieved by hybridizing its hydrophilic and hydrophobic cyclodextrin (CDs) complexes, i.e., those with hydroxypropyl-ß-cyclodextrin (HPßCD) andtriacetyl-ß-cyclodextrin (TAßCD),respectively. 1H-nuclearmagnetic resonance (1H-NMR) was performed to examine the interaction between both CDs and NC in solution. The solid complexes of NC : HPßCD and NC : TAßCD were prepared, in a 1 : 1 molar ratio by the spray-drying method. Complexation in the solid state was demonstrated by differential scanning calorimetry (DSC) and powder X-ray diffractometry. In vitro dissolution studies were carried out in simulated gastric (pH 1.2) and intestinal (pH 6.8) fluids, according to the USP basket method. The 1H-NMR studies provided clear evidence of an interaction between the CDs and the aromatic rings of NC. The DSC thermograms of the solid complexes showed no endothermic peak due to NC melting and their diffraction pattern was completely diffuse, which suggested the formation of a novel type solid phase with an amorphous character. The low dissolution rate of NC, a weak basic drug, in alkaline medium was significantly improved by complexation with HPßCD. In contrast, the in vitro release of this drug from the NC : TAßCD complexes was markedly retarded in both dissolution media. An optimal formulation was then designed by the combination, in different molar ratios, of these two complexes. The release behavior of these preparations was investigated and it was observed that the retarding effect was dependent on the amount of the NC : TAßCD complex. In addition, the initial release rate became faster as the molar ratio of the NC : HPßCD complex increased

Nanoencapsulation I. Methods for preparation of drug-loaded polymeric nanoparticles

Polymeric nanoparticles have been extensively studied as particulate carriers in the pharmaceutical and medical fields, because they show promise as drug delivery systems as a result of their controlled- and sustained-release properties, subcellular size, and biocompatibility with tissue and cells. Several methods to prepare nanoparticles have been developed during the last two decades, classified according to whether the particle formation involves a polymerization reaction or arises from a macromolecule or preformed polymer. In this review the most important preparation methods are described, especially those that make use of natural polymers. Advantages and disadvantages will be presented so as to facilitate selection of an appropriate nanoencapsulation method according to a particular application.http://www.sciencedirect.com/science/article/B7MDB-4JH72D0-3/1/fd4828f502f6e3c7e40643c9b4dbfea

Multicomponent complex formation between vinpocetine, cyclodextrins, tartaric acid and water-soluble polymers monitored by NMR and solubility studies

This work deals with multicomponent complex formation of vinpocetine (VP) with [beta]-cyclodextrin ([beta]CD), sulfobutyl ether [beta]-cyclodextrin (SBE[beta]CD) and tartaric acid (TA), in the presence or absence of water-soluble polymers, in aqueous solution. Complexation was monitored by phase-solubility and proton nuclear magnetic resonance (1H NMR) studies. TA demonstrated a synergistic effect on VP solubility, and in the complexation efficiency of [beta]CD and SBE[beta]CD. Additionally, water-soluble polymers increased even more the complexation efficiency of the CDs that was reflected by a 2.1-2.5 increase on KC values for VP-CD-TA-polymer multicomponent complexes. SBE[beta]CD was more effective in VP solubilization, as KC values of VP-SBE[beta]CD-TA multicomponent complexes were notably higher than in corresponding [beta]CD complexes. The large chemical shift displacements from protons located in the interior of the hydrophobic CD cavities (i.e., H-3 and H-5) coupled with significant chemical shift displacements of VP aromatic protons suggested that this moiety was included in the cavity of both [beta]CD and SBE[beta]CD. Two-dimensional rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments were carried out in order to obtain information about the multicomponent complex geometry in solution. Inspection of ROESY spectra allowed the establishment of spatial proximities between all aromatic protons of VP and the internal protons of the CDs, confirming that the aromatic moiety of VP is included in CD cavities being deeply inserted in SBE[beta]CD multicomponent complexes, since additional interactions with the sulfobutyl side chains were evidenced.http://www.sciencedirect.com/science/article/B6T25-4DT2KX7-1/1/a543ba03bff16fe4ef579956893c94b

Prostate carcinoma and stem cells

[Abstract] Stem cells, as classically defined, are cells with a capacity to self-renew and to generate daughter cells that can differentiate down several cell lineages to form all of the cell types that are found in the mature tissue. Stem cells and tumour cells have many similar features, including infinite lifespan, self-renewal, multidrug resistance, telomerase expression and, in the instance of the prostate, androgen independence. Evidence supports a role for stem cells in the etiology of many types of cancer. The evolution of androgen-independent prostate carcinoma may reflect the emergence of stemlike prostate tumour cells. Because cancer may be a disease of stem cell lineages and Shh-Gli signalling controls the behaviour of precursors and of cells with stem cell properties in the mammalian tissues, prostate cancer might derive from inappropriate expansion of prostatic epithelial stem cell lineages caused by abnormal Shh-Gli function. This review attempts to integrate these recent results

Physico-chemical study of an exogenic fulgurite from a thunderstorm on 10th August 2013 in Dallas, TX

Droplet-like exogenic fulgurites comprise a minor grouplet of natural glasses resulting from powerful lightning strikes. Reports on such type-V fulgurites are scarce in the literature. In this work, a fulgurite specimen from the thunderstorm that took place on 10th August 2013, in Dallas, TX, USA, has been analyzed using X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared and Raman spectroscopy techniques. X-ray diffraction revealed the amorphous nature of the exofulgurite, and X-ray fluorescence showed a high Si, Al and Ca content. Infrared and Raman spectroscopy were key in revealing clear Si–O modes related signatures and a very significant presence of water (OH/H2O). A parallel with glassy silicate materials, but also with opal-A, was essential in the understanding of the fulgurite’s characteristics. In particular, Raman data evidenced the exofulgurite to have a high degree of depolymerization

Influence of feeding regimens on rat gut fluids and colonic metabolism of diclofenac-β-cyclodextrin

Feeding states may affect the performance of colonic prodrugs. The aim is to investigate the influence of feeding regimen in Wistar rats on: (i) distribution and pH contents along the gut and (ii) metabolism of two colonic prodrugs, diclofenac-β-cyclodextrin and a commercially available control, sulfasalazine, within the caecal and colonic contents. Male Wistar rats were subject to four different feeding regimens, the gut contents characterized (mass and pH) and the metabolism of prodrugs investigated. The feeding regimen affects gut contents (mass and pH), more specifically in the stomach and lower intestine, and affects the rate of metabolism of diclofenac-β-cyclodextrin, but not that of sulfasalazine. The latter's degradation is much faster than that of diclofenac-β-cyclodextrin while the metabolism of both prodrugs is faster in colonic (versus caecal) contents. Fasting results in most rapid degradation of diclofenac-β-cyclodextrin, possibly due to lack of competition (absence of food) for microbial enzymatic activity

Toxicological in vivo studies of an oral insulin nanosystem

http://www.sciencedirect.com/science/article/B6TCR-4PKH640-7G/1/31df064ec957f50aa568d739cd5d741

Binary Mutual Diffusion Coefficients of Isoniazid Aqueous Solutions at (298.15 and 310.15) K

Binary mutual diffusion coefficients measured by the Taylor dispersion method in two different laboratories (University of Naples, Federico II, Italy, and University of Coimbra, Portugal) are reported for aqueous solutions of isoniazid at concentrations from (0.000 to 0.100) mol·dm−3 and at two temperatures (298.15 and 310.15) K. The hydrodynamic radii for the isoniazid in aqueous solution are calculated from the experimental results. In addition, the Hartley equation and the experimental diffusion coefficients are used to estimate activity coefficients for aqueous isoniazid at both temperature

Mössbauer thermal scan study of a spin crossover system

Programmable Velocity equipment was used to perform a Mössbauer Thermal Scans to allow a quasi-continuous temperature study of the magnetic transition between the low-spin and a high-spin configurations in [Fe(Htrz)2(trz)](BF4) system. The material was studied both in bulk as in nanoparticles sample forms.Facultad de Ciencias ExactasInstituto de Física La PlataInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada