Synthesis And Application Of Dopamine And PEG Grafted Hydroxyethyl Starch

Hydroxyethyl starch(HES),a derivative of starch,is a water soluble semisyn-thetic polysaccharide used as a plasma volume expander and cryoprotectant.but it does not trigger an and has a very low risk of hypersensitivity and has a good biological compatibility in vivo.HES is getting more and more research attention for its non-toxic,non-stimulation,good hydrophilicity,complete biodegradeation,excellent biocompatibility and without immune response in vivo.In order to expand the application of hydroxyethyl starch,this thesis has designed and synthesized a new series of adhesive and biofouling-resistant polymer PEG-g-HES-g-DA.These polymers were deposited onto different materials to improve the biocompatibility.The research is mainly composed of the following aspects:(1)Amine-terminated poly(ethyleneglyeol)(NH2-PEG-NH2)was synthesized by two steps:Firstly,poly(ethyleneglyeol)tosylate(PEG-OTs)was prepared by esteri-fication of p-toluenesulfonyl chloaide and PEG catalyzed by triethylamine.Then,PEG-OTs reacted with NH3�H2O under high temperature and high pressure,followed by basification with NaOH.The resultant NH2-PEG-NH2 was characterized by 1HNMR and the amination yield was 80%.(2)A series of PEG-g-HES-g-DA polymers was synthesized by two steps:The HES was firstly activated via carbonyldiimidazole(CDI),and the CDI-activated HES then reacted with dopamine and NH2-PEG-NH2 in designed feeding ratio for 24 h.The reaction solution was then dialyzed in acidic aqueous atmosphere to remove the impurities and lyophilized.The PEG-g-HES-g-DA was characterized by UV-vis spectroscopy and 1HNMR to figure out its compositions.The total grafting ratio is up to 50%.(3)The synthesized polymer was deposited onto different materials to improve their biocompatibility.A direct drop coating method was used to modify glass,stainless steel and polycarbonate.Whereas,a poly(dopamine)sublayer was firstly fabricated on polypropylene and PTFE to facilitate the deposition of PEG-g-HES-g-DA polymers.The dynamic and static contact angle measurement confirmed that the hydrophilicity of the modified surfaces improved obviously and the polymer coatings could stablize on the material interfaces.(4)The hemocompatibility of the stable PEG-g-HES-g-DA coatings was evalued by protein adsorption and platelet adhesion experiments.The results showed that the modified material could suppress more than 70%of protein adsorption and resist more than 60%of platelet adhesion,indicating that these polymer coatings have good blood compatibility.This research has designed and synthesized a new series of adhesive and bio-fouling resistant polymer PEG-g-HES-g-DA.These polymer films,fabricated on different materials,could endow the modified surfaces with excellent biocompatibility.This coating construction process,forming a stable polymer coating on the surface without changing the nature of the material,was simple and versitile to various materials,providing promising strategies for the modification of biomaterials.