硅橡胶材料对血浆蛋白及血小板粘附作用的半体内试验

本文是研究三种血浆蛋白(γ—球蛋白、纤维蛋白原、白蛋白)在医用硅橡胶材料表面吸附的半体内同位素标记评价方法,同时由扫描电镜观察材料表面血小板粘附的数量和形态变化,从而评价国内外三种医用热硫化甲基乙烯基硅橡胶材料的血液相容性。研究结果表明:CHGB和DCGBE二种材料血液相容性相近,而STGB材料血液相容性较差。     

白蛋白固定的聚氨酯材料的血液相容性

与血液接触的医用材料用白蛋白进行表面处理后,可抑制血小板粘附、激活以及继而产生的血栓形成。尽管已被吸附的白蛋白能够改善材料的血液相容性,但当材料表面的白蛋白层与循环血液接触时,仍能迅速地发生能吸附作用。在本文中,作者将人血清白蛋白固定在聚氨酯(Pu)材料表面上,以研究其血液相容性及血液-材料相互作用方法的延伸效应。先用HMDI处理Pu材料表面,然后将白蛋白与Pu-HMDI接触,以便把白蛋白固定在Pu表面(P-u-Alb)。Pu-Alb材料表面具有富里叶衰减全反射红外光谱、电子能谱、扫描电镜以及动态接触角等方面的特征。通过蛋白质吸附、血小板粘附等体外试验,     

抗凝血生物材料的血液相容性

背景：专家们认为改善抗凝血生物材料的血液相容性,可以明显提高抗凝血生物材料的抗凝血性能。 目的：评价聚酯类和钛类抗凝血生物材料的血液相容性。 方法：以文献检索的方法探讨聚酯类和钛类抗凝血生物材料对血液中红细胞、血小板、白蛋白、纤维蛋白以及凝血因子等的影响,并通过溶血试验、动态凝血试验、血小板黏附试验、血清蛋白吸附试验、复钙试验以及乳酸脱氢酶释放试验等分析聚酯类和钛类抗凝血生物材料的抗凝血性能,从而评估聚酯类和钛类抗凝血生物材料的血液相容性。 结果与结论：聚酯类抗凝血生物材料及钛类抗凝血生物材料的溶血率明显降低,血小板黏附较少,白蛋白的吸附量增加,纤维蛋白原的吸附明显减少,复钙时间及凝血时间明显延长,表现出较高的抗凝血性能,具有良好的血液相容性,是较为理想的抗凝血生物材料。     

肝素化PEG与PVA水凝胶制备及凝血形成

过去认为生物材料血液相容性发展分为二个方面,一是药物活性剂的结合,如肝素(抑制纤维蛋白形成),或其它活性剂进入材料内部;二是引起材料表面最小有害的血液相互作用或产生蛋白吸附的有利因素。后者提出了许多假设,血液与血管内膜之间界面自由能为零的设想提出了对水凝胶的研究。表明了一种在水中低界面自由能的生物材料是一种非血栓形成材料,因此本文作者设想了水合聚乙二醇(PEG)的动力学特性及肝素处理改变聚乙烯醇(PVA)血液相容性,降低纤维蛋白,提高血小板相容性。选用PE管(内径1.67mm     

聚环氧乙烷硫代物、聚环氧乙烷或氟甲基接枝聚氨酯材料表面上的纤维蛋白原吸附

在探讨血液与医用材料之间的反应和研制与血液相容的医用材料中,研究蛋白质的吸附作用是非常重要的。众所周知,纤维蛋白不但是一种具有高度表面活性的蛋白质,而且也能产生瞬间粘附作用,即“vroman效应”。作者研究已报道具有较好血液相容性的氟化聚氨酯(Pu-PFDA)、聚环氧乙烷(PEO)接枝的聚氨酯(Pu-PEO)以及进一步硫化的Pu(Pu-PEO-SO_3)等材料表面的纤维蛋白原吸附现象。将Pu材料浸入内含14C-标记纤维蛋白原的牛血浆中,拿起后先用PBS缓冲液冲洗,然后再用2%SDS溶液冲洗。采用放射性     

聚谷氨酸苄酯/聚乙二醇嵌段共聚物膜的血液相容性研究

使用凝血时间实验、血小板的黏附和变形实验、血浆蛋白的吸附实验来评价聚谷氨酸苄酯 /聚乙二醇(PBL G/PEG)嵌段共聚物膜的血液相容性 ,PEG嵌段的引入对共聚物血液相容性的影响。结果表明 ,均聚物的血液相容性优于玻璃和硅油 ,共聚物的血液相容性优于均聚物 ,且随着 PEG含量增加 ,其血液相容性更好。     

利用抗人血小板膜糖蛋白Ⅲ_a单克隆抗体SZ—21测定生物材料表面粘附血小板数的新方法

本文介绍了一种新的生物材料血液相容性体外评价方法,用特异抗人血小板膜糖蛋白(GPⅢa)的单克隆抗体SZ-21以固相放射免疫法对人血清白蛋白、人血纤维蛋白原及鼠尾胶原镀膜材料管表面粘附血小板进行定量测定。 试验结果说明本研究建立的新方法可快速、准确、定量地测定生物材料吸附血小板的性能,并为进一步深入研究生物材料对蛋白抗原决定簇的影响提供了新的手段。     

生物碳素材料表面血小板黏附的实验研究

为了解生物碳素材料的凝血机制 ,将新鲜抗凝人血离心分离为富血小板血浆 ,在 37℃恒温条件下 ,对类金刚石薄膜 (DL C)、金刚石薄膜和石墨三种碳素材料进行了血小板黏附实验 ,通过扫描电镜对黏附于材料表面的血小板进行形态观察和计数分析 ,用形态指数描述血小板的变形程度。结果显示 ,DL C表面无血小板黏附 ,而金刚石薄膜和石墨表面均黏附有为数不少、呈 ～ 型重度变形的血小板。血小板的黏附量石墨最多 ,而形态指数则金刚石薄膜更大。经与前期研究和文献报道的对比分析 ,得出三个主要结论 :(1)蛋白吸附介导的血小板黏附、变形和聚集是生物碳素材料的主要凝血机制 ;(2 )评价生物碳素材料的血液相容性 ,血小板变形度比血小板消耗率更有价值 ;(3) DL C的纯度越高 ,血液相容性越好。这些结论对改进和设计新型碳素人工心瓣材料具有重要指导意义     

TiO2-x薄膜与热解碳血液相容性的对比研究

本文用血小板粘附试验证实了TiO2 x薄膜具有优于热解碳的血液相容性 ;并通过对材料表面 (界面 )能参数与血浆蛋白吸附关系的分析 ,阐述了两种材料表面蛋白质的不同吸附行为是导致其血液相容性差异的重要原因。     

TiO2-x薄膜与热解碳血液相容性的对比研究

本文用血小板粘附试验证实了TiO2-x薄膜具有优于热解碳的血液相容性;并通过对材料表面(界面)能参数与血浆蛋白吸附关系的分析,阐述了两种材料表面蛋白质的不同吸附行为是导致其血液相容性差异的重要原因.     

Protein adsorption to poly(ethylene oxide) surfaces.

Surfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted with bis-amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of 125I-labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low-molecular-weight PEO contained many more PEO molecules than the surfaces grafted with higher-molecular-weight PEO. The high-molecular-weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low-molecular-weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of "cooperative" water structuring around the larger PEO molecules may create an "excluded volume" of the hydrated polymer coils. This may be an important factor contributing to the observed low protein adsorption behavior.     

Mass spectrometric mapping of fibrinogen conformations at poly(ethylene terephthalate) interfaces

We have characterized the adsorption of bovine fibrinogen onto the biomedical polymer polyethylene terephthalate (PET) by performing mass spectrometric mapping with a lysine-reactive biotin label. After digestion with trypsin, MALDI-TOF mass spectrometry was used to detect peptides from biotinylated bovine fibrinogen, with the goal of identifying lysines that were more accessible for reaction with the chemical label after adsorption. Peptides within domains that are believed to contribute to heparin binding, leukocyte activation, and platelet adhesion were found to be biotin labeled only after bovine fibrinogen adsorbed to the PET surface. Additionally, the accessibility of lysine residues throughout the entire molecule was observed to increase as the concentration of the adsorbing bovine fibrinogen solution decreased, suggesting that the proximity of biologically active motifs to hydrophilic residues leads to their exposure. The surface area per adsorbed bovine fibrinogen molecule was quantified on PET using optical waveguide lightmode spectroscopy (OWLS), which revealed higher surface densities for bovine fibrinogen adsorbed from higher concentration solutions. By measuring changes in both the identity and conformation of proteins that adsorb from complex mixtures such as blood or plasma, this technique may have applications in fundamental studies of protein adsorption and may allow for more accurate predictions of the biocompatibility of materials.     

Biological responses to polyethylene oxide modified polyethylene terephthalate surfaces.

Polyethylene oxide (PEO) of molecular weights 5,000, 10,000, 18,500, and 100,000 g/mol was covalently grafted to surfaces of otherwise cell adhesive polyethylene terephthalate (PET) films. Analysis of these surfaces by measurement of contact angles and ESCA verified the presence of the grafted PEO. Protein adsorption assays of radiolabeled albumin and fibrinogen showed a marked reduction in adsorbed protein for the 18,500 and 100,000 molecular weight PEO coupled surfaces. Cell growth assays using human foreskin fibroblasts in culture showed that the higher-molecular-weight PEO surfaces supported cell growth to a much lower extent than the two lower-molecular-weight PEOs. Flow of whole blood over these surfaces and visualization of platelet adherence using epifluorescence video-microscopy showed very low platelet adherence only on the two higher-molecular-weight PEO coupled surfaces. Scanning electron microscopy corroborated these results. It was concluded that PEO of molecular weights neighboring 18,500 and higher was effective in reducing protein adsorption and cellular interactions on these surfaces.     

Lysine-PEG-modified polyurethane as a fibrinolytic surface: Effect of PEG chain length on protein interactions,platelet interactions and clot lysis

Fibrinolytic polyurethane surfaces were prepared by conjugating lysine to the distal terminus of surface-grafted poly(ethylene glycol) (PEG). Conjugation was through the α-amino group leaving the ε-amino group free. Lysine in this form is expected to adsorb both plasminogen and t-PA specifically from blood. It was shown in previous work that the PEG spacer, while effectively resisting nonspecific protein adsorption, was a deterrent to the specific binding of plasminogen. In the present work, the effects of PEG spacer chain length on the balance of nonspecific and specific protein binding were investigated. PEG–lysine (PEG-Lys) surfaces were prepared using PEGs of different molecular weight (PEG300 and PEG1000). The lysine-derivatized surfaces with either PEG300 or PEG1000 as spacer showed good resistance to fibrinogen in buffer. The PEG300-Lys surface adsorbed plasminogen from plasma more rapidly than the PEG1000-Lys surface. The PEG300-Lys was also more effective in lysing fibrin formed on the surface. These results suggest that the optimum spacer length for protein resistance and plasminogen binding is relatively short. Immunoblots of proteins eluted after plasma contact confirmed that the PEG–lysine surface adsorbed plasminogen while resisting most of the other plasma proteins. The hemocompatibility of the optimized PEG–lysine surface was further assessed in whole blood experiments in which fibrinogen adsorption and platelet adhesion were measured simultaneously. Platelet adhesion was shown to be strongly correlated with fibrinogen adsorption. Platelet adhesion was very low on the PEG-containing surfaces and neither surface-bound lysine nor adsorbed plasminogen promoted platelet adhesion.     

Methacrylate polymer layers bearing poly(ethylene oxide) and phosphorylcholine side chains as non-fouling surfaces: in vitro interactions with plasma proteins and platelets

Two methacrylate monomers, oligo(ethylene glycol) methyl ether methacrylate (OEGMA; MW = 300 g mol⁻¹, poly(ethylene glycol) (PEG) side chains of average length n = 4.5) and 2-methacryloyloxyethyl phosphorylcholine (MPC; MW = 295 g mol⁻¹), were grafted from silicon wafer surfaces via surface-initiated atom transfer radical polymerization. The grafted surfaces were used as model PEG and phosphorylcholine surface systems to allow comparison of the effectiveness of these two motifs in the prevention of plasma protein adsorption and platelet adhesion. It was found that at high graft density fibrinogen adsorption from plasma on the poly(MPC) and poly(OEGMA) surfaces for a given graft chain length was comparable and extremely low. At low graft density, poly(OEGMA) was slightly more effective than poly(MPC) in resisting fibrinogen adsorption from plasma. Flowing whole blood experiments showed that at low graft density the poly(OEGMA) surfaces were more resistant to fibrinogen adsorption and platelet adhesion than the poly(MPC) surfaces. At high graft density, both the poly(MPC) and poly(OEGMA) surfaces were highly resistant to fibrinogen and platelets. Immunoblots of proteins eluted from the surfaces after contact with human plasma were probed with antibodies against a range of proteins, including the contact phase clotting factors, fibrinogen, albumin, complement C3, IgG, vitronectin and apolipoprotein A-I. The blot responses were weak on the poly(MPC) and poly(OEGMA) surfaces at low graft density and zero at high graft density, again indicating strongly protein resistant properties for these surfaces. Since the side chains of the poly(OEGMA) are about 50% greater in size than those of poly(MPC), the difference in protein resistance between the poly(MPC) and poly(OEGMA) surfaces at low graft density may be due to the difference in surface coverage of the two graft types.     

The role of plasma proteins in cell adhesion to PEG surface-density-gradient-modified titanium oxide

Surface-density gradients of poly(ethylene glycol) (PEG) were fabricated, in order to carry out a systematic study of the influence of PEG chain density on protein adsorption and cell-adhesion behavior, as well as the correlation between them. Gradients with a linear change in coverage of the polycationic polymer Poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) were prepared on titanium dioxide surfaces by a controlled dipping process and characterized by variable-angle spectroscopic ellipsometry and fluorescence microscopy. The adsorption behavior of single proteins (fibrinogen and albumin) generally correlated with semiempirical geometric models, illustrating the effect of the PEG-chain surface distribution on the inhibition of protein adsorption. Distinct differences could be observed between individual adsorbing proteins, attributable to their mode of surface attachment. The single and competitive adsorption of protein solutions containing albumin and fibrinogen was then investigated by fluorescence microscopy, indicating a larger amount of fibrinogen adsorption compared with albumin adsorption (in minutes to hours) along the entire PLL-g-PEG gradient samples. To further elucidate the underlying mechanism of cell adhesion and spreading as a function of PEG coverage and the potential involvement of integrins, cell-adhesion assays were carried out with human foreskin fibroblasts (hFF). The use of surface-gradient samples demonstrated the importance for protein adsorption of PEG conformation, the amount of exposed titanium dioxide surface area (and its distribution), and the structure and chemistry of the proteins involved. Correspondingly the influence of these factors on cell adhesion could be directly observed, and insights gained into the roles of both nonspecific binding and specific integrin binding in cell adhesion.     

Fibrinogen adsorption, platelet adhesion and activation on mixed hydroxyl-/methyl-terminated self-assembled monolayers

The effect of surface wettability on fibrinogen adsorption, platelet adhesion and platelet activation was investigated using self-assembled monolayers (SAMs) containing different ratios of longer chain methyl- and shorter chain hydroxyl-terminated alkanethiols (C15CH3 vs. C11OH) on gold. Protein adsorption studies were performed using radiolabeled human fibrinogen (HFG). Platelet adhesion and activation studies with and without pre-adsorbed fibrinogen, albumin and plasma were assessed using scanning electron microscopy (SEM) and a glutaraldehyde-induced fluorescence technique (GIFT). Results demonstrated a linear decrease of HFG adsorption with the increase of OH groups on the monolayer (increase of the hydrophilicity). Platelet adhesion and activation also decrease with increase of hydrophilicity of surface. Concerning SAMs pre-immersed in proteins, fibrinogen adsorption was related with high platelet adhesion and activation. The passivant effect of albumin on platelet adhesion and activation was only demonstrated on SAMs contained C11OH. When all the blood proteins are present (plasma) platelet adhesion was almost absent on SAMs with 65% and 100% C11OH. This could be explained by the higher albumin affinity of the SAMs with 65% C11OH and the lower total protein adsorption associated with SAMs with 100% C11OH.     

Introduction of surface functional groups onto biomaterials by glow discharges

An attempt was made to graft the monomer HEMA to the polymer surface by "Glow discharge" technique. Experiments were carried out for different surfaces varying the exposure times of samples to HEMA and also as a function of glow discharge time. It was found that as the percentage of grafting increases the hydrophilicity also increases. Contact angle measurements were performed on these substrates, which confirmed the hydrophilic nature of the grafted samples compared to the controls. The role of protein adsorption and their effects to modulate the blood polymer interaction is briefly discussed. When a foreign material comes in contact with blood, the initial event is the adsorption of plasma proteins in parallel with the adhesion of platelets to the material. Albuminated surfaces discourage platelet adhesion while fibrinogen enhances the platelet attachment and thrombosis. Hence a decreased ratio of fibrinogen to albumin on a substrate can be correlated as an indication to its improved blood compatibility. Fibrinogen to albumin ratios of the grafted samples showed a reduction, indicating that albumin adsorption is high; which may make the modified surfaces non-thrombogenic.     

Fluorine doping into diamond-like carbon coatings inhibits protein adsorption and platelet activation

The first major event when a medical device comes in contact with blood is the adsorption of plasma proteins. Protein adsorption on the material surface leads to the activation of the blood coagulation cascade and the inflammatory process, which impair the lifetime of the material. Various efforts have been made to minimize protein adsorption and platelet adhesion. Recently, diamond-like carbon (DLC) has received much attention because of their antithrombogenicity. We recently reported that coating silicon substrates with fluorine-doped diamond-like carbon (F-DLC) drastically suppresses platelet adhesion and activation. Here, we evaluated the protein adsorption on the material surfaces and clarified the relationship between protein adsorption and platelet behaviors, using polycarbonate and DLC- or F-DLC-coated polycarbonate. The adsorption of albumin and fibrinogen were assessed using a colorimetric protein assay, and platelet adhesion and activation were examined using a differential interference contrast microscope. A higher ratio of albumin to fibrinogen adsorption was observed on F-DLC than on DLC and polycarbonate films, indicating that the F-DLC film should prevent thrombus formation. Platelet adhesion and activation on the F-DLC films were more strongly suppressed as the amount of fluorine doping was increased. These results show that the F-DLC coating may be useful for blood-contacting devices.     

Grafting of dermatan sulfate on polyethylene terephtalate to enhance biointegration

The aim of the present study was to achieve the immobilization of dermatan sulfate (DS) on polyethylene terephthalate (PET) surfaces and to evaluate its biocompatibility. DS obtained from the skin of Scyliorhinus canicula shark was immobilized via carbodiimide on knitted PET fabrics, modified with carboxyl groups. PET-DS characterization was performed by SEM, ATR-FTIR and contact angle measurements. Biocompatibility was evaluated by investigating plasma protein adsorption and endothelial cell proliferation, as well as by subcutaneous implantations in rats. The results indicated that DS immobilization on PET was achieved at ~8 μg/cm2. ATR-FTIR evidenced the presence of sulfate groups on the PET surface. In turn, contact angle measurements indicated an increase in the surface wettability. DS immobilization increased albumin adsorption on the PET surface, whereas it decreased that of fibrinogen. In vitro cell culture revealed that endothelial cell proliferation was also enhanced on PET-DS. Histological results after 15 days of subcutaneous implantation showed a better integration of PET-DS samples in comparison to those of nonmodified PET. In summary, DS was successfully grafted onto the surface of PET, providing it new physicochemical characteristics and biological properties for PET, thus enhancing its biointegration.