Endoscopic palliation for the obstructive jaundice caused by biliary or pancreatic malignant tumors is a commonly used medical treatment. However, plastic biliary stents are occluded by sludge deposition caused by bacterial adhesion in 3-5 months. Chitosan, which has both good biocompatibility and antimicrobial capability, was used to modify the inner surface of polyethylene (PE) tubing in this study. Chitosan was deposited onto the inner surface of oxidized PE tubing with the methanol precipitation technique. Attenuated total reflection/Fourier transform infrared and electron spectroscopy for chemical analysis indicated that the chitosan coating was feasible. Contact-angle measurements revealed that the surface hydrophilicity of the PE tubing increased with the chitosan coating. Morphological analysis with scanning electron microscopy showed that the PE surface became rougher and exhibited micropores after the chitosan coating. The adhesion of living Escherichia coli to chitosan-coated PE stents, characterized by the spreading plate method and scanning electron microscopy analysis, was more significant than that to unmodified stents after a 24-h phosphate-buffered saline or bile perfusion test. This finding may be attributed to the rougher and slightly positively charged surface of chitosan-coated PE tubing and to the OCH 3 hydrophobic functional groups in the chitosan structure. Because of its good biocompatibility, chitosan coated on the surface of PE can still be used for biliary stent applications with further chemical modification, such as sulfonation and quaternization, to increase its antimicrobial ability.
Photocrosslinkable polymers are clean and convenient materials for the biomedical uses. Chitosan, which owns excellent biocompatible and antimicrobial properties, is one of the choices while it is introduced with photosensitive functional groups. In this study, chitosan was N-phthaloylated to react with acryloyl chloride in the organic solvent homogeneously and the result has been verified by the solubility test. Fourier transformed infrared spectrometry and nuclear magnetic resonance spectrometer analysis indicated that the modification with the attachment of the photosensitive functional group, the acryloyl group, onto chitosan and poly(ethylene glycol) (PEG) was feasible. The differential scanning calorimetry analysis further indicated that the melting points of the N-phathaloylated chitosan were decreased as compared with the untreated chitosan control. Then photocrosslinkable chitosan derivative (CH-PAA) was photocopolymerized with PEG diacrylate (PEGA) under UV irradiation. The adhesion strength characterization and swelling capacity evaluation for this photocopolymer have shown obvious raises of the adhesiveness and water-adsorption abilities as compared with the photopolymer of CH-PAA.
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