Polymeric embolization coil of bilayered polyvinyl alcohol strand for therapeutic vascular occlusion: a feasibility study in canine experimental vascular models.

PURPOSE: To investigate the feasibility of polyvinyl alcohol (PVA) polymer coil as a new endovascular embolic agent and to gauge the related histologic response in a canine vascular model. MATERIALS AND METHODS: PVA polymer coil was fabricated by cross-linking PVA and tantalum particles. Basic properties were then studied in vitro via swelling ratio and bending diameter. Normal renal segmental arteries and wide-necked aneurysms of carotid sidewalls served as canine vascular models. Endovascular PVA coil embolization of normal renal segmental arteries (N = 20) and carotid aneurysms (N = 8) was performed under fluoroscopic guidance in 10 dogs. Degree of occlusion was assessed immediately and at 4 weeks after embolization by conventional and computed tomographic angiography. Histologic features were also graded at acute (day 1, six segmental arteries and four aneurysms) and chronic phases (week 4, 14 segmental arteries and four aneurysms) after embolization to assess inflammation, organization of thrombus, and neointimal proliferation. RESULTS: Swelling ratio declined as concentrations of cross-linking agent increased. Mean bending diameters were 2.05 mm (range, 0.86-6.25 mm) in water at 37 °C and 2.29 mm (range, 0.94-6.38 mm) in canine blood samples at 37 °C. Occlusion of normal renal segmental arteries was sustained (complete occlusion at day 1, n = 20; at week 4, n = 14), whereas immediate outcomes in carotid aneurysms (day 1, complete occlusion, n = 5; residual neck only, n = 3) were not sustained (week 4, complete occlusion, n = 1; minor recanalization, n = 1; major recanalization, n = 2). At week 4, chronic inflammatory cells predominated, with progressive organization of thrombus and fibrocellular ingrowth. All aneurysms bore full neointimal linings on the coil mass in the chronic phase. CONCLUSIONS: Vascular occlusion by PVA polymer coil proved superior in normal renal segmental arteries and feasible in surgically constructed carotid aneurysms (with packing densities ≥ 30%), constituting acceptable radiologic feasibility and histologic response.

Effect of mild alkali pretreatment on structural changes of reed (Phragmites communis Trinius) straw.

The effect of dilute sodium hydroxide (NaOH) on reed straw structural change at 105 degreeC temperature was evaluated in this study. Various concentrations of NaOH (1% to 2.5%) were used for pretreatment of reed straw at 105 degreeC for 10min. Scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy studies showed that 2% and 2.5% NaOH pretreated sample exposed more cellulose fibers compared with other treatments. The cellulose crystalline index was increased by the 1% to 2.0% NaOH treatments and slightly lowered by the 2.5% NaOH treatment due to destructing cellulose fibres. Two per cent NaOH pretreatment caused 69.9% lignin removal, whereas 2.5% NaOH pretreatment removed 72.4% lignin. Besides, reed straw, when pretreated at 2% and 2.5% NaOH, resulted 56.4% and 60.5% hemicellulose removal, respectively. However, the difference in removal of lignin and hemicellulose between 2% and 2.5% NaOH treated reed straw was very marginal. In addition, very negligible increase of cellulose level was estimated, amounting 78.8% and 76.6% in 2.5% and 2% NaOH-treated sample, respectively. Moreover, after 72 h, reducing sugar yield was 81.2% and 83.3% using enzyme loading of 15 FPU (g dry biomass)-' and 30 IU (g dry biomass)- and xylanase 4 FXU (g dry biomass)-1 from 2% and 2.5% NaOH pretreated reed straw, respectively. Reducing sugar yield was increased very marginally when NaOH concentration increased from 2% to 2.5% for reed straw pretreatment. Therefore, 2% NaOH is supposed to be effective for reed straw pretreatment at this mentioned condition.