Search

At deep-sea hydrothermal vents, a large source of potential chemical energy is created when reducing vent fluid and oxidizing seawater mix. In this environment, chemolithoautotrophic microbes catalyze exergonic redox reactions which in turn provide the energy needed to fuel their growth and the fixation of CO 2 into biomass. In addition to producing new organic matter, this process also consumes compounds contained both in vent fluid and entrained seawater ( e.g. H 2 , NO 3 − ). Despite their biogeochemical importance, such reactions have remained difficult to quantify due to methodological limitations. To address this knowledge gap, this study reports a novel application of isobaric gas-tight fluid samplers for conducting incubations of hydrothermal vent fluids at in situ temperature and pressure. Eighteen ~24 h incubations were carried out, representing seven distinct conditions that examine amendments consisting of different electron donors and acceptors. Microbial activity was observed in all treatments, and time series chemical measurements showed that activity was limited by electron acceptor supply, confirming predictions based on geochemical data. Also consistent with these predictions, the presence of nitrate increased rates of hydrogen consumption and yielded ammonium as a product of nitrate respiration. The stoichiometry of predicted redox reactions was also determined, revealing that the sulfur and nitrogen cycles are incompletely understood at deep-sea vents, and likely involve unknown intermediate redox species. Finally, the measured rates of redox processes were either equal to or far greater than what has been reported in previous studies where in situ conditions were not maintained. In addition to providing insights into deep-sea hydrothermal vent biogeochemistry, the methods described herein also offer a practical approach for the incubation of any deep-sea pelagic sample under in situ conditions. [ABSTRACT FROM AUTHOR]

Background: Plaque biofilm and associated host responses are the primary factors in the pathogenesis of periodontitis. Delivery of medications directly into the periodontal pockets to suppress or eradicate the pathogenic microbiota or modulate the inflammatory response has attracted significant interest to limit periodontal tissue destruction. The aim of the present study was twofold: (1) to describe the development of a biodegradable controlled-release device containing meloxicam as the therapeutic agent and (2) to evaluate the in vitro release of meloxicam from this device into different release media. Methods: Films of cross-linked gelatin matrix containing meloxicam were prepared, hardened for various time periods and cut in a form to fit to the periodontal pocket anatomy. The release of active agents was studied separately in 10 ml distilled water, artificial saliva and pH 7.4 phosphate buffer at 37°C. Apparatus Vibrax was used at 120 r.p.m. Determinations were carried out spectrophotometrically, and the release profiles were plotted as a function of time. The results were evaluated by the similarity test. Results: The release rates of meloxicam from the hardened (lh, 4h, 8 h) formulations were slower than the unhardened formulation in all the three release media. Increasing the hardening time decreased the release rates. The overall release rates were similar in artificial saliva and pH 7.4 phosphate buffer, while it was lower in distilled water. Conclusions: As a conclusion, cross-linked gelatin matrix films may be considered as a suitable inert material for obtaining a prolonged local release of meloxicam as an adjunct to the mechanical periodontal treatment. As required, further in vitro and in vivo studies will be performed before starting clinical applications of this controlled- release formulation of the anti-inflammatory agent. [ABSTRACT FROM AUTHOR]

Çetin EÖ, Buduneli N, Atlıhan E, Kırılmaz L: In vitro studies on controlled-release cellulose acetate films for local delivery of chlorhexidine, indomethacin, and meloxicam. J Clin Periodontol 2004; 31: 1117–1121. doi: 10.1111/j.1600-051X.2004.00620.x.© Blackwell Munksgaard, 2004.Delivery of medications into periodontal pockets to suppress or eradicate the pathogenic microbiota or modulate the inflammatory response, thereby limiting periodontal tissue destruction, has attracted significant interest with the purpose of effective periodontal treatment. However, no study has previously attempted to develop a controlled-release formulation of anti-inflammatory agents to be used in the field of periodontology. The aim of the present study was to examine the in vitro release profile of chlorhexidine gluconate, indomethacin, and meloxicam from cellulose acetate films.Cellulose acetate films containing chlorhexidine gluconate, indomethacin, and meloxicam were prepared and cut in a form to fit to the periodontal pocket anatomy. The release of active agents was studied in 10 ml artificial saliva at 37°C. Apparatus Vibrax was used at 150 r.p.m. Determinations were carried out spectrophotometrically and the release profiles were plotted as a function of time.The formulations showed two different release patterns for a total observation period of approximately 120 h. When the formulations of the three active agents were compared, the release patterns of meloxicam and chlorhexidine gluconate were found to be similar, while the indomethacin-containing formulation exhibited the fastest release rate.As a conclusion, cellulose acetate may be a suitable inert material for obtaining a prolonged local release of various anti-inflammatory agents like meloxicam. Further in vitro and in vivo studies are required before starting clinical applications of these controlled-release formulations of anti-inflammatory agents. [ABSTRACT FROM AUTHOR]

Objectives. The use of drug delivery systems in dentistry is a relatively new area of research with the exception of fluoride ion release from polyalkenoate cements and their predecessor silicate cements. The present study is based on the use of a bio-compatible material ethylene vinyl acetate copolymer (EVA) that enables constant release of drugs of therapeutic levels over extended periods of time at doses suitable for the treatment of oral conditions.Method. Polymer casting solutions were made by dissolving EVA and the drug in the ratio of 40:1 in 70 ml of dichloromethane at 38 °C for 6 h. Thin square films of 3×3 cm2 with a thickness of 1 mm were cut from the dry sheet obtained by solvent evaporation technique. Drug loaded samples were extracted for a minimum of 14 days in 10 ml medium (double distilled water or water/ethanol (4:1)) which was replaced daily. Spectral measurements were made to follow changes in optical densities (OD) during release kinetics. Effect of temperature (24 and 37 °C) on the rate of drug release was studied and the energies of activation (ΔE≠) were calculated using Arrehenius equation for the diffusion (translocation) of molecules of tetracycline hydrochloride (TTH), doxycycline hydrochloride (DOH), and chlorhexidine diacetate (CDA) in water as extracting medium. Effect of extracting medium (water and water/ethanol (4:1)) was also investigated on the rate of drug release measurements at 24 °C.Results. Analysis of variance of the data revealed that significantly enhanced rates were observed at the higher temperature (37 °C) and when extracting medium was changed to water/ethanol (4:1) for TTH, DOH and CDA (p<0.0015). The enhanced rate values seem to be due to the formation of channels in the polymer. The largest activation energy (21.83 kcal mol−1) observed for CDA was interpreted as due to the highest average molecular weight (626) compared to TTH (481) and DOH (481).Significance. These in vitro rate of drug release measurements will provide a basis for establishing a novel approach (treatment modality) for sustained intra-oral drug delivery over extended time periods using laboratory methods and materials that are readily available to dentists. [Copyright &y& Elsevier]