Development and initial testing of valves opened by Valsalva (abdominal straining):Proof of principle for urinary catheters or male urethra

We hypothesised that raising the abdominal pressure could provide a non-manual approach to opening a urinary valve, with potential application for indwelling catheters or an intraurethral device. The ‘Vysera’ valve remains closed during short high amplitude spikes but opens when a pre-defined low-amplitude pressure is maintained for a pre-specified duration, allowing sustained abdominal straining to achieve voluntary opening. The valve was subjected to in vitro performance and microbiological tests. Parameters for valve specification were selected by review of a large urodynamic database with nominal opening pressure of 75 cmH2O +/-15 cmH2O (range 60-90 cmH2O) and valve pressure was refined using early clinical results. Valve housings were designed for the end of a Foley catheter, and for male post-prostatectomy intraurethral placement. Preliminary clinical evaluation was undertaken for both designs, incorporating qualitative feedback. In vitro testing of the catheter valve demonstrated only minimal encrustation. On clinical evaluation of the catheter-sited value, six of seven patients (86%) were able to open the valve intentionally by straining. When inactive, none of the patients experienced leakage (7/7=100%), while five (71%) leaked when they coughed. The intraurethral device was successfully placed with image intensifier guidance under general anaesthetic in five of nine patients. Three patients used the device; initial leakage resolved as patients mobilised. However, in contrast to the catheter-sited valve, the intraurethral device was difficult to tolerate for even a few hours. Removal was performed under local anaesthesia with a flexible cystoscope and stent grasper. We conclude that storage and bladder emptying using a strain-activated valve are feasible for a catheter valve and an intra-urethral device. The valve parameters need to be matched to individual patients. For the intraurethral device, additional development is needed to improve the stent housing and valve performance

Fabrication and characterization of gefitinib-releasing polyurethane foam as a coating for drug-eluting stent in the treatment of bronchotracheal cancer

The purpose of the present study was to develop gefitinib-loaded polymeric foams that can be used as coating of drug-eluting stents for palliative treatment of bronchotracheal cancer. Release of such an anticancer drug from such stent coating can retard tumor regrowth into the bronchial lumen. Gefitinib-loaded polyurethane (PU) foams were prepared by embedding either gefitinib micronized crystals or gefitinib-loaded poly(lactic-co-glycolic acid) microspheres in water-blown films, with up to 10% w/w loading for gefitinib microcrystals and 15% w/w for gefitinib microspheres (corresponding to 1.0% w/w drug loading). Drug-release studies showed sustained release of gefitinib over a period of nine months, with higher absolute release rates at higher drug loading content. By the end of the studied nine month release periods, 60-100% of the loaded gefitinib had been released. Foams loaded with gefitinib-PLGA microspheres at 15% w/w showed accelerated drug release after 4 months, coinciding with the degradation of PLGA microparticles in the PU foam as demonstrated by scanning electron microscopy (SEM). When applied on a nitinol braided bronchotrachial stent, PU coatings with gefitinib microspheres showed similar mechanical properties as the drug-free PU coating, which indicated that the loading of microspheres did not affect the mechnical properties of the PU foams. In conclusion, we have fabricated drug-loaded PU foams that are suitable for bronchotracheal stent coating