Investigation of Prolonged Drug Release from Matrix Formulations of Chitosan

A hydrocolloidal matrix system containing complexes of chitosan was investigated for preparation of sustained release tablets and examined in-vitro.

Theophylline tablets using chitosan as a sustained release base were evaluated. It was found that when chitosan is used in a concentration of more than 50% of tablet weight, an insoluble non-erosion type matrix was formed. Tablets prepared with a chitosan concentration of less than 33% were fast releasing.

Chitosan used in a concentration of about 10% acted as a disintegrant and the drug was dissolved within an hour.

Citric acid slowed down the release rates of chitosan based theophylline tablets. Theophylline tablets using carbomer-934P as a sustained release base were evaluated. Carbomer-934P in lower concentrations forms an erosion type matrix. In order to produce a twenty-four (24) hour sustained release tablet, more than 10% concentration of carbomer-934P is needed. Combination with chitosan and carbomer-934P produced slower releasing tablets.

A hydrocolloidal erosion type matrix was formulated using chitosan, carbomer-934Pand citric acid. Only 10% of chitosan was needed to prepare theophylline sustained release tablets in these mixtures.

The dose dumping potential of chitosan tablets due to rapid disintegration in alkaline media was eliminated by preparing hydrated erosion type matrix systems.     

Wall-to-bed heat transfer characteristics of spout-fluid beds

Wall-to-bed heat transfer characteristics have been investigated in a rectangular spout-fluid (S–F) bed segment column (20 cm length, 5 cm width and 50 cm height) utilizing glass beads (D_p = 0.254, 0.388 and 0.461 mm) and air as fluid. Results indicate that h values in the S–F bed increase with increasing air mass velocity and particle diameter, and decrease with increasing bed height. Under identical flow conditions h values in the S–F bed were about 30% more than for the corresponding fluidized bed.     

Very Important Publication: Hypoiodite‐Catalyzed Regioselective Oxidation of Alkenes: An Expeditious Access to Aldehydes in Aqueous Micellar Media

A highly anti‐Markovnikov selective oxidation of alkenes based on in situ generated hypoiodite catalysis in aqueous micellar media under mild conditions has been described. This novel catalytic system realizes an efficient synthesis of aldehydes from alkenes in an economically viable and environmentally safe fashion. The preliminary mechanistic studies suggest that the reaction proceeds via tandem iodofunctionalization/1,2‐aryl or alkyl migration. The scope and limitations of this tandem process are demonstrated with various mono‐ and disubstituted (terminal and internal) olefins.

     

Fungal sinusitis: progression of disease in immunosuppression--a case report

Fungal sinusitis is a disease which can be grouped into invasive and noninvasive forms. The invasive entities include the acute/fulminant and chronic/indolent forms. The noninvasive entities include the fungus ball and allergic forms. The noninvasive forms, however, can develop into invasive disease under certain immunosuppressive states. The patient in this case report had the fungus ball form of fungal sinusitis which evolved into chronic, and then the acute/fulminant form approximately two weeks after undergoing cadaver-donor kidney transplantation. Due to the patient's immunosuppressed state, the fungus spread beyond the sinus region and eventually lead to fulminant disseminated disease. The severity of the fungal disease corresponded directly to the severity of the patient's immunosuppression.     

Synergism between resveratrol and other phytochemicals: implications for obesity and osteoporosis

Resveratrol, a phytoalexin, has gained much attention recently due to its effects on sirtuins. While the anti-cancer properties of resveratrol have been extensively investigated, the anti-adipogenic and osteogenic effects of resveratrol are also gaining considerable interest. The finding that resveratrol supplementation mimics caloric restriction prompted researchers to study the effects of resveratrol on lipid metabolism. Mesenchymal stem cells are the precursors for both adipocytes and osteoblasts. In the aging population, differentiation to adipocytes dominates over the differentiation to osteoblasts in bone marrow, contributing to the increased tendency for fractures to occur in the elderly. Thus, an inverse relationship exists between adipocytes and osteoblasts in the bone marrow. Resveratrol acts on several molecular targets in adipocytes and osteoblasts leading to a decrease in adipocyte number and size and an increase in osteogenesis. Furthermore, resveratrol in combination with genistein and quercetin synergistically decreased adipogenesis in murine and human adipocytes. A recent in vivo study showed that phytochemicals including resveratrol in combination with vitamin D prevented weight gain and bone loss in a postmenopausal rat model. Therefore, combinations of resveratrol with other phytochemicals may lead to potential novel potent therapies for both obesity and osteoporosis.     

Hot-melt coating: water sorption behavior of excipient films

Hot-melt coating allows encapsulation of water-labile, drug-laden substrates to form a barrier that resists moisture ingress. To understand the interaction of water with excipients that can form moisture-protective coatings, sorption behavior of films of lipidic (glyceryl behenate) and polymeric (polyvinyl alcohol) coating excipients was investigated. A simple and rapid method using a new, fully automated instrumental technique to investigate the sorption/desorption behavior of excipient films is reported. Further, the influence of temperature and film thickness on the sorption behavior of films is examined. Both excipient films displayed sorption isotherms that were classified as type III and demonstrated hysteresis during desorption. The sorption data for both films did not follow the Langmuir model, and the BET model could only be used restrictively. The GAB model fitted the sorption data at all conditions and over the entire range of water activity studied. The ability of the Young and Nelson model to explain the hysteresis behavior, from analytical and mechanistic perspectives, is evaluated. Temperature and film thickness were found to profoundly influence the nature of moisture interaction and distribution of moisture in the excipient films. An Arrhenius-type relationship was observed between equilibrium moisture content of excipient films and temperature at constant water activity.     

Three-dimensional chemical imaging of embedded nanoparticles using atom probe tomography

Analysis of nanoparticles is often challenging especially when they are embedded in a matrix. Hence, we have used laser-assisted atom probe tomography (APT) to analyze the Au nanoclusters synthesized in situ using ion-beam implantation in a single crystal MgO matrix. APT analysis along with scanning transmission electron microscopy and energy dispersive spectroscopy (STEM-EDX) indicated that the nanoparticles have an average size ~8-12 nm. While it is difficult to analyze the composition of individual nanoparticles using STEM, APT analysis can give three-dimensional compositions of the same. It was shown that the maximum Au concentration in the nanoparticles increases with increasing particle size, with a maximum Au concentration of up to 50%.