低温等离子体对NiTi形状记忆合金的表面改性

在微波电子回旋共振低温等离子体条件下,用二乙二醇二甲醚为试剂对镍钛合金进行表面改性.在表面得到一层均匀、致密的固体薄膜.经过X射线光电子能谱和衰减全反射傅立叶变换红外光谱的分析和表征,发现沉积的涂层为类PEG结构,表面主要聚集大量-CH2-CH2-O键;血浆蛋白吸附实验显示,与改性前相比,等离子体沉积在镍钛合金表面的类PEG涂层能够有效抵抗蛋白质吸附.     

低温等离子体改性铝合金及其表面性质的研究

通过在铝合金表面制备等离子体聚合物薄膜以减少蛋白质吸附,提高铝合金生物相容性.采用四乙二醇二甲醚为有机试剂,在电子回旋共振低温微波等离子体条件下,在铝合金表面制备了一层涂层,用X-ray光电子能谱、衰减全反射红外光谱和血浆蛋白吸附试验对涂层进行分析表征.结果表明:铝合金表面沉积的涂层均匀、致密,其化学组成为类PEG结构,主要聚集大量碳氢和碳氧极性键;与改性前相比,等离子体沉积在铝合金表面的类PEG涂层能够有效抵抗蛋白质吸附.     

低温等离子体改性铝片降低细菌粘附的研究

铝片在二(乙二醇)甲醚／微波电子回旋共振(ECR Plasma)低温等离子体条件下进行处理．表面得到一层均匀、致密的涂层。经过电子光谱化学分析(XPS)、衰减全反射红外光谱(ATR-FTIR)、原子力显微镜(AFM)和生物活性的分析和表征,发现沉积的涂层为类PEG结构,表面主要聚集大量-CH2-CH2-O键;与改性前相比,等离子体处理的铝片表面能极大地降低细菌粘附。     

NiTi合金表面低温等离子体接枝类PEG研究

众所周知表面接枝类聚乙二醇(PEG)可以改善材料的生物相容性.本文研究了氧/二(乙二醇)甲醚低温等离子体条件下NiTi合金表面接枝PEG结构及其性质.经X射线光电子能谱(XPS)、衰减全反射红外光谱(ATR-FTIR)、扫描电镜(SEM)和水接触角的分析和表征,证实沉积的涂层为类PEG结构,表面主要聚集大量(-CH2-CH2-O)n键;与改性前相比,接枝后的NiTi合金亲水性有较大提高.     

316L不锈钢支架表面EVAL涂层的制备及性能研究

采用超声-喷涂沉积的方法,在316L不锈钢表面制得聚乙烯-乙烯醇涂层。利用原子力显微镜、接触角测量仪及扫描电镜对涂层表面形貌及性能进行研究。结果表明,316L不锈钢基体、S-EVAL涂层和USEVAL涂层的表面粗糙度Ra分别为123.677,14.994和2.830 nm。S-EVAL涂层和US-EVAL涂层表面接触角分别为75.6和74.3°,均小于316L不锈钢基体接触角。超声-喷涂沉积US-EVAL涂层血小板粘附量最少。     

铝合金表面微波等离子体类聚乙二醇涂层的亲水性研究

通过对铝合金低温微波等离子体表面改性,增强其亲水性,减少铝离子扩散,降低生物学毒性,可提高铝合金的生物相容性.采用三乙二醇二甲醚有机试剂,于电子回旋共振低温微波等离子体条件下,在铝合金表面进行沉积对其改性,对所得涂层用X射线光电子能谱、衰减全反射红外光谱和水接触角进行分析表征,以判断表面沉积物的组成及亲水性变化,评价低温微波等离子体处理对提高铝合金亲水性的机理及作用.结果表明,铝合金经三乙二醇二甲醚低温微波等离子体改性后,表面得到一层均匀、致密的涂层,其化学组成为类聚乙二醇结构,表面主要聚集有大量的碳氢和碳氧极性键;与改性前相比,等离子体涂装的铝合金表面接触角大大下降.低温微波等离子体表面改性能显著提高铝合金表面的亲水性.     

医用钛合金表面改性的研究进展

从金属植入体与生物环境的界面反应,以及钛植入体表面现阶段存在的主要问题出发,叙述了近年来钛表面生物活性、生物相容性、血液相容性、抗菌性涂层的制备、结构及性能,重点总结了应用等离子体喷涂技术制备羟基磷灰石涂层、硅酸盐陶瓷涂层、纳米ZrO2涂层、纳米TiO2涂层,以及采用等离子体浸没离子注入/沉积技术对钛合金表面进行离子注入和薄膜沉积的研究结果.最后,基于钛硬组织植入体表面需求,指出钛硬组织植入体表面改性设计与制备应注重改性层的综合生物学性能及力学安全性.     

等离子体增强电弧离子镀1Cr17Ni2不锈钢表面氮化/DLC涂层复合改性研究

在等离子体增强电弧离子镀设备中,用热丝增强放电的辉光等离子体对1Cr17Ni2马氏体不锈钢进行表面氮化处理。对氮化层的表面形貌、成分、相结构及性能进行了测试及分析。结果表明,氮化处理后不锈钢的表面硬度从3.67 GPa最高提升到9.25 GPa,并且在50μm深的范围内保持7.32 GPa以上的硬度,改性层内有CrN和Fe_2N新相生成是硬化的主要原因,不过与基体相比,摩擦系数仅从1.1略微降低到0.9。在氮化预处理的基础上,再一体化用碳靶阴极弧等离子体对1Cr17Ni2钢进行氮化/DLC涂层复合改性处理,对表面DLC涂层改性层的品质及性能进行了测试与分析。结果表明,复合改性处理后,因表面得到1.5μm厚的高品质的DLC涂层,及氮化预处理使得表面硬度有梯度提升,使1Cr17Ni2钢的整体表面硬度进一步提高到17.06 GPa,且摩擦系数显著降低到0.08。     

等离子体聚合沉积聚烯丙胺薄膜改性聚酯及体外血小板粘附研究

采用脉冲和连续波方式沉积等离子体聚烯丙胺薄膜改性聚酯(PET)材料表面,并进一步在等离子体聚烯丙胺薄膜表面固定肝素分子.利用衰减全反射红外光谱、X射线光电子能谱和接触角测试等离子体聚烯丙胺薄膜的元素成分、组成和表面能,采用对三氟甲基苯甲醛衍生法和甲苯胺蓝法分别检测了等离子体聚烯丙胺薄膜表面的伯胺基浓度和固定肝素分子的聚烯丙胺薄膜表面的肝素浓度.实验结果表明,脉冲等离子体聚合薄膜PPAa-P表面的伯胺基浓度为1.4%,而连续波等离子体聚合薄膜PPAa-C表面伯胺基浓度只有0.71%.等离子体聚烯丙胺薄膜改性的PET的表面能增加,其中PPAa-P改性的PET表面的表面能的极性分量增加较大.脉冲等离子体聚烯丙胺薄膜表面固定的肝素浓度为4.07μg/cm2,为连续波等离子体聚烯丙胺薄膜表面固定肝素浓度2.23μg/cm2的1.8倍.体外血小板粘附实验结果表明,表面肝素化的PET表面有较低数量的血小板粘附和激活,尤其是在固定肝素分子的脉冲等离子体聚烯丙胺薄膜改性的PET表面表现出更好的抗凝血性.     

射频等离子体放电的宏观参数与PET表面改性的关系

通过射频等离子体放电，采用O2，CF4及CH4／CF4混合气体等离子体对PET表面进行处理。改变射频等离子体放电的宏观参数，如放电时间、放电功率、电极间距离和复合参数，详细地研究了这些参数对PET表面改性的影响。结果表明：碳氟混合气体等离子体在PET表面的沉积速率为正值，在PET表面形成了聚合物；而O2和纯CF4气体的沉积速率为负值，两者在PET表面产生刻蚀效应。增加等离子体放电功率和放电时间，聚合或刻蚀效果更明显；而增加电极间距离和复合参数，聚合或刻蚀效果明显减弱。     

Cold Plasma Surface Modification of NiTi for Biomedical Applications

Surface-grafted poly(ethylene glycol) (PEG) molecules are known to prevent protein adsorption to the surface. Nitinol samples were coated under tetraglyme ECR cold plasma conditions to enhance its biocompatibility. The modified Nitinol surfaces were characterized by high resolution ESCA and contact angle, it was demonstrated that the deposited PEG-like coatings were built up mainly of-CH2-CH2-O- linkages in surfaces. The surface wettability of the modified Nitinol was increased compared with the control surface. Human plasma protein was adsorbed on Nitinol evaluated by SEM, the protein adsorption on modified surfaces decreased rapidly. Thus, the potential benefits of cold plasma technique will be of use to the biomedical industries improving the biocompatibility of metals.     

Collagen coating on hydroxyapatite surfaces modified with organosilane by chemical vapor deposition method

Type I collagen was coated onto the modified surfaces of hydroxyapatite (HAp) sintered body. The interfacial interaction between collagen and HAp in a nano-region was controlled by depositing the organosilane of n-octadecyltrimethoxysilane (ODS: -CH3) or aminopropyltriethoxysilane (APTS: -NH2) with a chemical vapor deposition method. The surfaces were elaborated by X-ray photoelectron spectroscopy, zeta-potential, and contact angle measurements; the Si and/or N peaks were detected, and the contact angles and surface energies were apparently different on the modified surfaces. The morphologies of collagen adsorbed on the surfaces of HAp and HAp deposited with APTS were similar, however that of the surface with ODS was apparently different, due to the hydrophobic interaction between the organic head group of -CH3 and residual groups of collagen.     

Effects of adsorbed heat labile serum proteins and fibrinogen on adhesion and apoptosis of monocytes/macrophages on biomaterials

A previously established human monocyte culture protocol was used to determine the effects of varying adsorbed proteins on monocyte/macrophage adhesion and survival on dimethyl-silane (DM) or RGD modified glass coverslips. Cells were allowed to adhere for 2 h in the absence of protein or in the presence of serum, fibrinogen (Fg), heat inactivated serum (HIS), serum supplemented with Fg or HIS with Fg. Cell adhesion and apoptosis rates were determined on days 0 (2 h), 3, 7 and 10 of culture. The presence of serum alone in the initial culture was sufficient to optimize monocyte/macrophage adhesion and survival rates. Adding Fg to serum did not increase adhesion nor decrease apoptotic rates. No protein or the addition of HIS during the initial incubation period significantly decreased monocyte/macrophage adhesion and survival on both surfaces, however, the addition of Fg to HIS restored adhesion and survival rates to those seen with in the presence of serum alone on RGD surfaces. These studies demonstrate that monocyte/macrophage adhesion and survival on biomaterial surfaces are optimized by adsorbed heat labile serum proteins while adsorbed Fg plays a surface property-dependent role.     

Analysis of rat plasma proteins desorbed from gold and methyl- and hydroxyl-terminated alkane thiols on gold surfaces

It is believed that adsorbed blood or plasma components, such as water, peptides, carbohydrates and proteins, determine key events in the concomitant inflammatory tissue response close to implants. The aim of the present study was to develop a procedure for the collection and analysis of minor amounts of proteins bound to solid metal implant surfaces. The combination of a sodium dodecyl sulfate washing method coupled with a polyacylamide gel electrophoretic protein separation technique (SDS–PAGE), Western blot and image analysis enabled the desorption, identification and semiquantification of specific proteins. The analyzed proteins were albumin, immunoglobulin G, fibrinogen and fibronectin. Concentration procedures of proteins were not required with this method despite the small area of the test surfaces. The plasma proteins were adsorbed to pure gold and hydroxylated and methylated gold surfaces, which elicit different tissue responses in vivo and plasma protein adsorption patterns in vitro. The image analysis revealed that the pure gold surfaces adsorbed the largest amount of total and specific proteins. This is in accordance with previous ellipsometry/antibody experiments in vitro. Further, the principles described for the protein analysis can be applied on implant surfaces ex vivo. ©©2000 Kluwer Academic Publishers     

Characterization of proteins and fibroblasts on thin inorganic films

The ability of biomaterial surfaces to regulate cell behavior requires control over surface chemistry and material microstructure. One of the goals in the development of silicon-based biomedical devices such as biosensors or drug delivery systems is improved biocompatibility which may be achieved through the deposition or adsorption of thin films. In this study, films of single crystal silicon, stoichiometric and low stress silicon nitride, doped and undoped polysilicon, as well as Arg-Gly-Asp (RGD) peptide adsorbed surfaces characterized in terms of protein adsorption or cellular adhesion for a period of four days. Protein adsorption studies using fibrinogen and albumin, two proteins implicated in cellular adhesion and surface activity, reveal that low stress silicon nitride surfaces have a 223%±2.50% greater protein adsorption compared to undoped polysilicon surfaces, followed by silicon nitride, unmodified silicon, and doped polysilicon surfaces, respectively. The thickness of the adsorbed albumin and fibrinogen layer on various thin films was measured by ellipsometry and compared to contact angle measurements. The greatest cellular adhesion was observed on undoped polysilicon, followed by unmodified (control) silicon, low stress silicon nitride, silicon nitride, and doped polysilicon surfaces. Cellular binding supports the differential protein adsorption found on modified and unmodified silicon surfaces. Understanding the biological response to thin films will allow us to design more appropriate interfaces for implantable diagnostic and therapeutic silicon-based microdevices.     

Preliminary study on human protein adsorption and leukocyte adhesion to starch-based biomaterials

In this study, the adsorption of human serum albumin (HSA), fibronectin (FN) and vitronectin (VN) onto the surface of novel biodegradable materials was evaluated by immunostaining. Specifically, polymeric blends of corn starch with cellulose acetate (SCA), ethylene vinyl alcohol copolymer (SEVA-C), and polycaprolactone (SPCL) were immersed in unitary and competitive systems; that is, binary and more complex protein solutions. For binary solutions, different HSA and FN protein distribution patterns were observed depending on the starch-based surface. Furthermore, the relative amount of proteins adsorbed onto starch-based surfaces was clearly affected by protein type: a preferential adsorption of VN and FN as compared to HSA was observed. On tests carried out with unitary, binary and more complex solutions, it was found that vitronectin adsorption ability was enhanced in competitive systems, which was associated with a lower amount of adsorbed albumin. In order to assess the effect of these human proteins on cell behavior, a mixed population of human lymphocytes and monocytes/macrophages was cultured over pre-coated SEVA-C surfaces. Through anti-CD3 and CD-14 monoclonal antibody labeling and cell counting, leukocyte adhesion onto pre-coated SEVA-C surfaces was analyzed. Based on the results, it was possible to detect albumin long-term effects and fibronectin short-term effects on cell adhesion proving that previously adsorbed proteins modulate leukocyte behavior.     

The effect of nanoscale surface curvature on the oligomerization of surface-bound proteins

The influence of surface topography on protein conformation and association is used routinely in biological cells to orchestrate and coordinate biomolecular events. In the laboratory, controlling the surface curvature at the nanoscale offers new possibilities for manipulating protein–protein interactions and protein function at surfaces. We have studied the effect of surface curvature on the association of two proteins, α-lactalbumin (α-LA) and β-lactoglobulin (β-LG), which perform their function at the oil–water interface in milk emulsions. To control the surface curvature at the nanoscale, we have used a combination of polystyrene (PS) nanoparticles (NPs) and ultrathin PS films to fabricate chemically pure, hydrophobic surfaces that are highly curved and are stable in aqueous buffer. We have used single-molecule force spectroscopy to measure the contour lengths L_c for α-LA and β-LG adsorbed on highly curved PS surfaces (NP diameters of 27 and 50 nm, capped with a 10 nm thick PS film), and we have compared these values in situ with those measured for the same proteins adsorbed onto flat PS surfaces in the same samples. The L_c distributions for β-LG adsorbed onto a flat PS surface contain monomer and dimer peaks at 60 and 120 nm, respectively, while α-LA contains a large monomer peak near 50 nm and a dimer peak at 100 nm, with a tail extending out to 200 nm, corresponding to higher order oligomers, e.g. trimers and tetramers. When β-LG or α-LA is adsorbed onto the most highly curved surfaces, both monomer peaks are shifted to much smaller values of L_c. Furthermore, for β-LG, the dimer peak is strongly suppressed on the highly curved surface, whereas for α-LA the trimer and tetramer tail is suppressed with no significant change in the dimer peak. For both proteins, the number of higher order oligomers is significantly reduced as the curvature of the underlying surface is increased. These results suggest that the surface curvature provides a new method of manipulating protein–protein interactions and controlling the association of adsorbed proteins, with applications to the development of novel biosensors.     

Contributions of adhesive proteins to the cellular and bacterial response to surfaces treated with bioactive polymers: case of poly(sodium styrene sulfonate) grafted titanium surfaces

The research developed on functionalized model or prosthetic surfaces with bioactive polymers has raised the possibility to modulate and/or control the biological in vitro and in vivo responses to synthetic biomaterials. The mechanisms underlying the bioactivity exhibited by sulfonated groups on surfaces involves both selective adsorption and conformational changes of adsorbed proteins. Indeed, surfaces functionalized by grafting poly(sodium styrene sulfonate) [poly(NaSS)] modulate the cellular and bacterial response by inducing specific interactions with fibronectin (Fn). Once implanted, a biomaterial surface is exposed to a milieu of many proteins that compete for the surface which dictates the subsequent biological response. Once understood, this can be controlled by dictating exposure of active binding sites. In this in vitro study, we report the influence of binary mixtures of proteins [albumin (BSA), Fn and collagen type I (Col I)] adsorbed on poly(NaSS) grafted Ti6Al4V on the adhesion and differentiation of MC3T3-E1 osteoblast-like cells and the adhesion and proliferation of Staphylococcus aureus (S. aureus). Outcomes showed that poly(NaSS) stimulated cell spreading, attachment strength, differentiation and mineralization, whatever the nature of protein provided at the interface compared with ungrafted Ti6Al4V (control). While in competition, Fn and Col I were capable of prevailing over BSA. Fn played an important role in the early interactions of the cells with the surface, while Col I was responsible for increased alkaline phosphatase, calcium and phosphate productions associated with differentiation. Poly(NaSS) grafted surfaces decreased the adhesion of S. aureus and the presence of Fn on these chemically altered surfaces increased bacterial resistance ≈70 % compared to the ungrafted Ti6Al4V. Overall, our study showed that poly(NaSS) grafted Ti6Al4V selectively adsorbed proteins (particularly Fn) promoting the adhesion and differentiation of osteoblast-like cells while reducing bacterial adhesion to create a bioactive surface with potential for orthopaedic applications.     

Deposition of cellular fibronectin and desorption of human serum albumin during adhesion and spreading of human endothelial cells on polymers

More insight into the mechanism of adhesion of human endothelial cells (HEC) on to polymeric surfaces may lead to the development of improved small-diameter vascular grafts. HEC suspended in 20% human serum-containing culture medium adhere and spread well on moderately water-wettable polymers such as tissue culture polystyrene (TCPS). Earlier it was demonstrated that during adhesion and spreading of HEC on TCPS, cellular fibronectin is deposited on to this surface. It was postulated that fibronectin deposition is accompanied by desorption of adsorbed serum proteins, e.g. human serum albumin (HSA). The amounts of adsorbed (cellular) fibronectin and HSA on TCPS surfaces pretreated for 1 h with solutions of human serum (ranging from 0.01%–20%), were determined after incubation of these surfaces for 6 h with HEC in culture medium and after incubation with culture medium without cells. Protein adsorption was determined by means of a two-step enzyme-immunoassay (EIA). HEC adhesion and spreading on TCPS resulted in a significant deposition of fibronectin irrespective of the serum concentration in the solution used for the pretreatment of TCPS. The deposition of cellular fibronectin on to TCPS, pretreated with human serum, was accompanied by displacement of adsorbed HSA. Desorption of HSA from TCPS was only detectable with the EIA at serum concentrations ranging from 0.01%–1%. Using¹³¹-l-labelled HSA as tracer protein; it could, however, be demonstrated that HSA was also displaced from TCPS, pretreated with solutions of higher serum concentrations. Pretreatment of the hydrophobic vascular graft material PET (poly(ethylene terephthalate); Dacron) and of FEP (fluoroethylenepropylene copolymer; a Teflon-like polymer) with a solution containing 20% human serum resulted in a reduced adhesion of HEC compared to uncoated surfaces. We suggest that this may be caused by a poor displacement of adsorbed serum proteins from these hydrophobic surfaces by cellular fibronectin. This may explain why HEC normally fail to adhere on to prosthetic surfaces.