The Development And Antimicrobial Experimental Study Of The Nano Silver / Polyurethane Biliary Stent

ObjectiveBiliary stent has been widely used for palliative care in a variety of benign and malignant bile duct stenosis. Its clinical effect in the near future is significant, but long-term patency of the stent is limited by blockage. Studies have shown that many factors may lead to bile duct restenosis, such as bacterial biofilm formation, deposition of biliary sludge, bile duct hyperplasia , endometrial tumor growth of granulation tissue , and so on.The nano-silver materials are prone to contact with pathogenic microorganism due to quantum effect, small size effect and great specific surface area, therefore displaying more biologic effect and more disadvantages such as wide antibacterial range and long disinfection time. Therefore,our team tried to use nano-silver to improve the antibacterial performance of stent in order to reduce the risk of blockage of the stent.MethodsNew Nano silver / polyurethane (Ag / PU) antibacterial hydrophilic bile duct stent has been developed in two parts, antibacterial experiments and animal experiments conducted for future clinical trials,which can help to provide a theoretical basis for further evaluation and application. Ag / PU antibacterial material was prepared by in situ reduction for in vitro antibacterial tests .Besides,three groups were setted : the experimental group (Ag / PU film), positive control group(silver nitrate paper) and negative control group(normal polyurethane materials ). Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and enterococci were spreading on beef extract plate for inhibition zone test.Each inhibition zone diameter was measured and data were analyzed.Based on its good in vitro antibacterial efficiency, animal experiments were carried out for further research. an animal model of suppurative cholangitis was made through endoscop. Swines were randomly allocated into four groups:normal group, model group, Ag / PU group and PU group. Ag / PU stent and PU stent were respectively placed in the common bile duct of Ag / PU group and PU group with the puepose of comparing the antibacterial activity. Blood samples aspirated from the thoracic vein were analyzed for Inflammatory cytokines (IL-1β, TNF-α), leukocyte count, neutrophil count, serum bilirubin, and AKP / ALP. Finally,all the pigs were killed, then bile ducts were taken for histological examination . The bacterial adhesion degree for PU stent and Ag NPs/PU stent is presented by fluorescence and SEM images.ResultsWe found that the inhibitory effect of Ag / PU composite against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and enterococci in vitro are as good as that of the silver nitrate paper, the difference beteen Ag / PU composite and the silver nitrate paper was not statistically significant.Swines of Ag / PU stent group showed lighter inflammation, infection than other groups of animals. We found bacteria is not easily absorbed in the surface of Ag / PU stent, its local antibacterial effect stent can prevent restenosis of bile duct.ConclusionAg / PU composite has good antibacterial effects as well as good stability,therefore, our group will further explore in the near future to make it to clinical application.