Fibrinolytic Multifunctional Blood Contact Surfaces
Surface-induced clotting and thrombus formation is the major reason for the failure of blood-contacting devices.A lot of work are focused on developing blood-contacting materials with long-term hemocompatibility.Materials that are "bioinert" and/or "bioactive" in various ways have been proposed for the construction of blood-contacting materials.However,despite of many years of effort,a truly blood compatible material has not yet been developed.For cardiovascular implants materials,it is necessary to inhibit the clot formation on the surface.However,it is also important to inhibit neointimal hyperplasia caused by smooth muscle cell(SMC)interactions.It therefore seems reasonable to develop multifunctional material surfaces for the final goal of truly blood compatible biomaterials.For the above ideas,firstly,based on the traditional antithrombotic strategy and fibrinolytic strategy,a series of multifunctional surfaces based on fibrinolysis were constructed.The advantage and problem of these surface modification strategies were investigated.Secondly,the general one-pot strategies adopted by previous studies suffer the problem of inevitable competition between diverse biomolecules and uncontrollability of the relative quantities of the immobilized biomolecules,as well as the influence on the activities of the immobilized biomolecules caused by multiple-step of chemical modification.To solve these problems,a new sequential co-immobilization strategy based on chemical modification and host-guest interaction was proposed and applied to fabricate a blood compatible surface.This thesis aims to explore and design a series blood contacting material surfaces which have antithrombotic ability and preventing restenosis.Detailed research contents are as follows:(Ⅰ)Two monomers,namely oligo(ethylene glycol)methyl ether methacrylate(OEGMA)and a lysine-containing methacrylic monomer(LysMA),were graft copolymerized on a vinyl-functionalized polyurethane(PU)surface,the resulting surface is referred to as PU-POL.Using this one-step polymerization method,we developed a multifunctional PU surface with protein-resistance and clot lysing properties.In addition,selenocystamine,which catalyzes the release of nitric oxide(NO)from S-nitrosothiols(RSNOs)(endogenous NO donors in blood),was immobilized covalently on the modified surface.Thereby,a bifunctional surface(PU-POL-Se)with both fibrinolytic activity and NO releasing ability was realized.This surface was shown to generate NO in the presence of S-nitrosoglutathione(GSNO)at a rate of 0.61 × 10-10 mol cm-2 min-1,comparable to that of healthy endothelium(0.5×10-10-1.0 × 10-10 mol cm-2 min-1).A dual functioning surface with fibrinolytic activity(lysis of nascent clots)and NO releasing ability(inhibition of platelet adhesion and smooth muscle cell(SMCs)adhesion as well as proliferation)was thereby constructed.(Ⅱ)Immobilization of selenocystamine decreased the lysine density of the PU-POL and subsequently affected the plasminogen(Pig)adsorption of the surface.In this further work,the two double bond monomers,2-hydroxyethyl methacrylate(HEMA)and 1-adamantan-1-ylmethyl methacrylate(AdaMA)were graft copolymerized on a vinyl-functionalized PU surface,the resulting surface is referred to as PU-PHA.In addition,selenocystamine was immobilized covalently on the modified surface,the resulting surface is referred to as PU-PHA-Se.Finally,lysine containing β-cyclodextrin(CD-L)and sulfonated β-cyclodextrin(CD-S)were immobilized on PU-PHA-Se via host-guest interactions between adamantine residues and CD-L or CD-S respectively.The PU-PHA-Se/CD-L surface not only could inhibit human umbilical vein smooth muscle cells(HUVSMCs)adhesion and proliferation and inhibit platelets adhesion and activation,but also could adsorb Pig specifically from plasma(165 ng/cm2).The PU-PHA-Se/CD-S surfac showed excellent anticoagulant ability and promoted endothelialization.This work provides a new method for the construction of multifunctional material surface and solves the problem of inevitable competition between diverse biomolecules and uncontrollability of the relative quantities of the immobilized biomolecules.(Ⅲ)The three double bond monomers,HEMA,LysMA and AdaMA were graft copolymerized on a vinyl-functionalized PU surface to give PU-PHLA.The heparin-like component,CD-S,was immobilized on PU-PHLA via host-guest interactions between admantane residues and CD-S.The PU-PHLA/CD-S surface could adsorb Pig specifically from plasma(200 ng/cm2),and have excellent anticoagulant ability(the PRT prolonged 14 min compared to unmodified PU surface),promote endothelialization(the density of human umbilical vein endothelial cells(HUVECs)on PU-PHLA/CD-S after 48 h culture increased by 130%)and inhibit SMCs adhesion(inducing the expression of contractile HUVSMCs phenotype markers)at the same time,also could inhibit platelets adhesion and activation.This strategy can not only solve the problem of clot formation during the implantation of blood contacting materials,but also give the ability of promoting endothelialization and inhibiting SMCs adhesion to the materials,making the materials suitable for both short-term and long-term blood contact applications.(Ⅳ)Multilayered polyelectrolyte films containing "guest" moieties were first fabricated using the layer-by-layer(LBL)deposition of chitosan and poly(sodium 4-vinylbenzenesulfonate-co-AdaMA),followed by the incorporation of CD-L as "host" molecules with Pig specifically adsorption ability(Au-LBL/CD-L).The Au-LBL/CD-L surface showed excellent anticoagulant and fibrinolytic activities,promoted endothelialization,inhibited SMCs adhesion,as well as killed bacteria at the surface interface(make E.coli surface shrinkage and death).The combination of LBL and host-guest interaction provides a new method for the construction of multifunctional blood contact material surfaces.