Intercalated theophylline-smectite hybrid for pH-mediated delivery

On the basis of their large specific surface areas, high adsorption and cation exchange capacities, swelling potential and low toxicity, natural smectite clays are attractive substrates for the gastric protection of neutral and cationic drugs. Theophylline is an amphoteric xanthine derivative that is widely used as a bronchodilator in the treatment of asthma and chronic obstructive pulmonary disease. This study considers the in vitro uptake and release characteristics of the binary theophylline-smectite system. The cationic form of theophylline was readily ion exchanged into smectite clay at pH 1.2 with a maximum uptake of 67±2 mg g−1. Characterisation of the drug-clay hybrid system by powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy confirmed that the theophylline had been exclusively intercalated into the clay system in an amorphous form. The drug remained bound within the clay under simulated gastric conditions at pH 1.2; and the prolonged release of approximately 40% of the drug was observed in simulated intestinal fluid at pH 6.8 and 7.4 within a 2-h timeframe. The incomplete reversibility of the intercalation process was attributed to chemisorption of the drug within the clay lattice. These findings indicate that smectite clay is a potentially suitable vehicle for the safe passage of theophylline into the duodenum. Protection from absorption in the stomach and subsequent prolonged release in the small intestine are advantageous in reducing fluctuations in serum concentration which may impact therapeutic effect and toxicit

Preparation of stable acrylate/montmorillonite nanocomposite latex via in situ batch emulsion polymerization: Effect of clay types

WOS: 000280886500029Nanocomposites based on acrylic (butyl acrylate-co-methyl methacrylate-co-acrylamide) terpolymer and various commercial montmorillonites were synthesized by an "in situ" batch emulsion polymerization method. A complex emulsifier system containing sodium dodecyl sulphate (SDS) and a polymeric stabilizer was used in the polymerization. The minimum emulsifier concentration necessary to obtain stable latex depended on nanoparticle type and was established by several trials. Based on the experimental data two groups of stable latexes were obtained and characterized. The first nanocomposite latex group (Group A) was obtained by using lower emulsifier content and included Cloisite 93A, Cloisite 30B, Nanomer 1.31 PS, Cloisite Na(+) clays while the second group (Group B) had higher emulsifier content including Cloisite 15A, Cloisite 20A, Dellite 67G and Nanomer 1.44P clays. The nanocomposite emulsions were characterized by means of particle size and zeta potential analyzes. The intercalation/exfoliation of the nanoparticles in acrylic latex was assessed by XRD and SEM. The structural characterizations of the nanocomposite films were performed by FTIR, mechanical properties were tested by DMTA and thermal behavior was analyzed by DSC and TGA. The zeta potential and particle size analysis showed that nanocomposite latexes were electrostatically stable and they had fine particle sizes varying between 94 and 174 nm with narrow distributions. DMTA results indicated significantly enhanced elastic moduli values for the nanocomposites except of those containing the clays having a relatively more hydrophilic nature (DOB, CNa(+)). The nanocomposite films also exhibited increased thermal stabilities. It was concluded that the clay type used in the preparation of nanocomposites and the emulsifier content in emulsion polymerization play important roles in determining latex and polymer properties of the nanocomposites and they should be predetermined for each application field. (C) 2010 Elsevier B.V. All rights reserved.EOL [FP7-NMP-2007-CSA-1]The authors acknowledge the support of the EOL through the FP7-NMP-2007-CSA-1 project NaPolyNet: Setting up research-intensive clusters across the EU on characterization of polymer nanostructure for performing several analyses (XRD, DSC, Particle size analysis, etc.)

Polysaccharide Containing Gels for Pharmaceutical Applications

WOS: 000456875000007Bio-derived polymers are falling into the needs of pharmaceutical formulations for topical applications due to their gelling ability. Generally, in topical delivery, as an alternative way for local and systemic application of active substances, formulations in gelling form are preferred as they have multiple advantages, e.g., minimize systemic side effects, avoid gastrointestinal irritation, prevent the metabolism of the active substance in liver, etc. The present chapter reviews bio-based polymers with special reference to polysaccharides-based hydrogels with respect to their pharmaceutical applications