Evaluation Of Hydroxybutyl Chitosan And Genipin For Cardiovascular Stent

Cardiovascular diseases (CVDs) are the main cause of death globally, including disorders that can affect the heart and the blood vessels, leading to myocardial infarction and peripheral artery disease. Percutaneous transluminal coronary angioplasty (PTCA), based on stent implantation, has been an important procedure in the treatment of cardiovascular diseases, particularly coronary vascular disease(CAD). There are three kinds stents:bare metal stent, drug-eluting stent and biodegradable stent. Because bare-metal stents and drug-eluting stent can cause varying degrees of in stent restenosis, so biodegradable stent is developed to solve the blood vessel blockage problem and does not cause in-stent restenosis.In this paper, by etherification reaction, hydroxybutyl chitosan(HBC) is synthesized based on chitosan. The basic property and chemical property and biocompatibility of HBC are tested and evaluated. HBC crosslinks with genipin to form a polymeric and biodegradable stent. The stent could maintain the perfect spiral shape. The biocompatibility and biodegradability of the stent are tested. These results provide the basis for fabricating a new kind biodegradable stent.Under basic alkaline condition, chitosan reacts with 1,2-butylene through etherification process to produce the soluble HBC. HBC has a temperature sensitive property, at a particular temperature can be converted between the fluid and the solid state. FTIR spectroscopy experiments show etherification substitution reaction occurs mainly at the 6-OH site and a small portion also occurs at the 2-NH2 site in chitosan molecules. HBC’s molecular weight as compared with chitosan decreased a lot. With a rheometer the temperature-sensitive property is proved and the gelling temperature is tested. The internal structure of the gel is detected by scanning electron microscopy and is macro porous network structure. This structure determines HBC could used in biomedical field.The biocompatibility evaluation of HBC include two aspects:blood compatibility and cell compatibility. The hemolysis experiment results show that the hemolysis rate of HBC is lower than chitosan and the different concentration HBC’s hemolysis rate are all under 5%, which is corresponding to the country’s requirement. MTT method is used to evaluate the different concentrations of HBC extract’s effects on Human Umbilical Vein Endothelial Cells (HUVECs). The cells’relative proliferation rate are all above 80% indicating the HBC is a qualified material.The solution casting method is used to make the HBC film and the film crosslinks with the genipin solution to fabricate the polymeric biodegradable stent. The stent could maintain the perfect spiral shape. The solution’s ionic strength and the crosslink time of the fabricating process are optimized. The stent’s mechanical property and flexibility are the optimum which fabricated under 0.02M PBS and crosslinking for 3h.In the protein absorption experiment, the amount of the protein absorbed by HBC stent is lower than the chitosan stent. The HBC stent’s hemolysis rate is less than 5%, having good blood compatibility. In the MTT assay, the HUVECs relative proliferation rate of the different concentration HBC stent is all above 80%, claimed qualified material. In the vitro degradation experiments, the lower the stent’s crosslinking degree, the more easily the stent degrades. The HBC stent which crosslinking time is 3h, degrades faster. The stent fabricated by HBC and genipin have good biocompatibility and biodegradability and can be used to further study cardiovascular stents.