The Stent Patency and Migration Rate of Different Shaped Plastic Stents in Bile Flow Phantom Model and In Vivo Animal Bile Duct Dilation Model.

BACKGROUND/AIM: In research and development of biliary plastic stents (PS), continuous efforts have been made to overcome short patency time and high rate of migration. The aim of this study was to evaluate the patency and migration rate of different PS shapes for a given period of time. METHODS: Using an in vitro bile phantom model, we compared the patency among different shapes of PS (three straight PS, four double-pigtail PS, and a new screw-shaped PS). We performed an analysis of the degree of luminal narrowing by light microscopic examination. Using an in vivo swine model, we compared the patency and migration rate among the three different types of PS. RESULTS: Eight weeks after the bile exposure in the bile flow phantom model, 80 PS were retrieved and analyzed. The straight PS showed less biofilm formation and luminal narrowing than other types of PS (p < 0.05). Forty-nine PS were inserted into the dilated bile ducts of 10 swine models, and 39 PS were successfully retrieved 8 weeks later. The stent migration occurred less frequently in the double-pigtail PS and the screw-shaped PS than it did in the straight PS (11.1, 10, and 27.3%, respectively). However, there was no statistical difference in stent patency among the different shapes. CONCLUSIONS: Stent patency may not be significantly different depending on the shape of PS for 8 weeks. The screw-shaped PS showed similar patency and migration rate to the double-pigtail PS. These results may help guiding future PS development and clinical decisions.

Bio-sheet graft therapy for artificial gastric ulcer after endoscopic submucosal dissection: an animal feasibility study.

BACKGROUND: Various bio-sheet grafts have been attempted either to accelerate healing of artificial ulcers or to prevent adverse events after endoscopic submucosal dissection (ESD), but neither prospective nor mechanistic studies were available. OBJECTIVE: To evaluate the substantial effect of a bio-sheet graft on artificial ulcer healing and its feasibility as an endoscopic treatment modality. DESIGN: Preclinical, in vivo animal experiment and proof-of-concept study. SETTING: Animal laboratory. SUBJECTS: Three mini-pigs, Sus scrofa, mean age 14 months. INTERVENTION: Multiple ulcers sized 2.5 cm in diameter were generated by ESD in 3 mini-pigs and were assigned randomly into the following 3 groups; control group, bio-sheet group, or combination (bio-sheet plus drug) group. Bio-sheet grafts or bio-sheet plus drug combinations were applied on the artificial ulcers immediately after the ESD. MAIN OUTCOME MEASUREMENTS: Feasibility and efficacy of endoscopic bio-sheet graft therapy for the management of artificial ulcers and the evaluation of healing conditions based on histology changes in the remaining gastric bed tissues harvested from the stomachs. RESULTS: Thirty-three ESD specimens were obtained. On an image analysis of the ratio of healed area in the remaining gastric bed tissue compared with the matched dissected gastric mucosa, the control group showed the most significant improvement in healing activity among the 3 groups (P < .05), whereas the severity of inflammation in the remaining ulcer tissue was significantly attenuated in bio-sheet and combination groups (P < .05). LIMITATIONS: Animal model. CONCLUSION: Although the bio-sheet grafts provided physical protection from gastric acid attack as reflected in the attenuated inflammation on the ulcer beds, unexpected delayed ulcer healing was noted in the bio-sheet graft group because of its physical hindrance of the healing process.

Optimal reproduction of a porcine benign biliary stricture model using endobiliary radiofrequency ablation.

The use of endobiliary radiofrequency ablation (RFA) to generate a benign biliary stricture (BBS) model has a significant reproducibility problem. The aims of this animal study were to create an optimal BBS model using endobiliary RFA and determine the best way to develop it. The first step was performed on the common bile duct (CBD) of 10 miniature pigs using endoscopic RFA with a target temperature-controlled mode (80 â„ƒ, 7 W for 90 s). The second step was performed on the CBD of five miniature pigs to understand more about the time-dependent changes in BBS development and the causes of adverse events. Using the conditions and techniques identified in the previous steps, the third step was conducted to create an optimal BBS model in 12 miniature pigs. In the first trial, four out of 10 animals died (40%) after the procedure due to cholangitis-induced sepsis. Based on this, biliary obstruction was prevented in further steps by placing a biliary plastic stent after RFA application. Histologic examinations over time showed that a severe abscess developed at the RFA application site on the fifth day, followed by fibrosis on the tenth day, and completion on the twentieth day. In the third trial, 11 animals survived (91.7%), the average BBS fibrotic wall thickness was 1107.9 µm (763.1-1864.6 µm), and the degree of upstream biliary dilation was 14.4 mm (11.05-20.7 mm). In conclusion, endobiliary RFA combined with a biliary plastic stent resulted in a safe and reproducible BBS animal model.

Bile Flow Phantom Model and Animal Bile Duct Dilation Model for Evaluating Biliary Plastic Stents with Advanced Hydrophilic Coating.

BACKGROUND/AIMS: The efforts to improve biliary plastic stents (PSs) for decreasing biofilm formation and overcome short patency time have been continued. The aim of this study is to evaluate the effect of advanced hydrophilic coating for patency and biodurability of PS. METHODS: Using an in vitro bile flow phantom model, we compared patency between prototype PS with hydrophilic coating (PS+HC) and prototype PS without hydrophilic coating (PS-HC). We performed an analysis of the degree of luminal narrowing by microscopic examination. Using an in vivo swine bile duct dilation model made by endoscopic papillary closure and stent insertion, we evaluated biodurability of hydrophilic coating. RESULTS: In the phantom model, PS+HC showed less biofilm formation and luminal narrowing than PS-HC at 8 weeks (p<0.05). A total of 31 stents were inserted into the dilated bile duct of seven swine models, and 24 stents were successfully retrieved 8 weeks later. There was no statistical difference of stent patency between the polyethylene PS+HC and the polyurethane PS+HC. The biodurability of hydrophilic coating was sustained up to 8 weeks, when assessing the coating layer by scanning electron microscopy examination. CONCLUSIONS: Advanced hydrophilic coating technology may extend the patency of PS compared to uncoated PS.

Specific molecular structure changes and radical evolution during biomass-polyethylene terephthalate co-pyrolysis detected by (13)C and (1)H solid-state NMR.

Co-pyrolysis of biomass with polyethylene terephthalate (PET) was studied as a function of blend ratio and co-pyrolysis temperature by (13)C and (1)H solid-state nuclear magnetic resonance (NMR). The (13)C NMR spectra showed that upon heating to 400°C in presence of the biomass, the formation of crystallites in PET was completely suppressed and that at higher temperatures there was increased formation and growth of the polycyclic aromatic hydrocarbons (PAHs). This change in the PET degradation behaviour was attributed to the presence of radicals formed in char from biomass. The measurement of the (1)H-T1 relaxation enabled monitoring the changes in the concentrations of radicals formed, as a function of the blend ratios and the co-pyrolysis temperatures. It indicated that the increase in the radical concentrations correlated well with the increased degradation of the PET and growth of PAHs.