Oct 09, 2014 Posted Under: Drugs

The drug concentrations in the buffer

To compare the PCL stents manufactured in this study with the commercial 10-mm-covered Ultraflex SEMSs, both PCL (10 mm in diameter) and Ultraflex stents were compressed by a 1-N force, and the deformation rates were recorded. Area load was applied over the full length of the stents with a 1,500-mm2 plate mounted on a LLOYD tensiometer. The cross-head speed was 1 mm/min.

An in vitro elution method was used to determine the release characteristics of cisplatin from the stents. A phosphate buffer, 0.15 mol/L (pH 7.4), was used as the dissolution medium buy Australia Cialis. The stents’ elements were placed in glass test tubes with 1 mL of phosphate buffer. All tubes were incubated at 37°C. The dissolution medium was collected daily for subsequent HPLC analyses. Fresh phosphate buffer (1 mL) was then added for the next 24-h period, and this procedure was repeated for 6 weeks.

The drug concentrations in the buffer for the elution studies were determined by a HPLC assay standard curve for cisplatin. The HPLC analyses were conducted on a Hitachi D-2000 Elite Delivery System. The column used for separation of the cisplatin was a Zorbax ODS, C18, 5 mm, 4.6 cm X 250 mm HPLC column. The mobile phase contained distilled water and acetonitrile (10/90, volume/volume). The absorbency was monitored at 280 nm, and the flow rate was 2.0 mL/min. All samples were assayed in triplicate, and sample dilutions were performed to bring the unknown concentrations into the range of the assay standard curve. A calibration curve was made for each set of the measurements (correlation coefficient > 0.99). The elution product can be specifically identified and quantified with high sensitivity using the HPLC system.

Fifteen New Zealand white rabbits, with an average weight of 3.0 kg, were divided into five groups in this study. During the surgical procedure, the animals were anesthetized with an intramuscular injection of 1 mL 2% xyla-zine hydrochloride and 1 mL 50% tiletamine/50% zolazapam (both as hydrochloride). All rabbits maintained spontaneous breathing without intubation. The cervical trachea was exposed. A longitudinal incision was made at the midline of the trachea, crossing six cartilage rings, starting from the third. The 6-mm PCL stent was implanted under direct vision. The tracheotomy was then closed with a polypropylene suture. All animal procedures received institutional approval.

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