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1.
Coating of surfaces by RGD peptides is well-known. Herein we describe the possibility to switch cell adhesion properties by changing the distance and orientation of the RGD peptides to the surface. A set of RGD peptides of the type cyclo(-RGDfK-) was synthesized containing the photoswitchable 4-[(4-aminophenyl)azo]benzocarbonyl central unit as spacer between the acrylamide anchor and the RGD peptide. PMMA (poly methyl methacrylate) surfaces were coated with these peptides. Control of adhesion stimulation by irradiation with 366 or 450 nm light could be achieved.  相似文献   

2.
Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was applied to validate GRGDS peptide patterned surfaces. The structuring of the surfaces included several steps: micro contact printing (μCP), chemical etching and aminofunctionalization followed by chemical coupling of spacer-linked GRGDS peptides via an isothiocyanate anchor. TOF-SIMS analysis of characteristic ions and molecular fragments with a lateral resolution of 100 nm allowed proving the change in chemical properties of the surface with each step during the structuring process. We found that the application of polydimethylsiloxane as stamp material resulted in the contamination of the surface with this polymer. TOF-SIMS investigations, however, also showed that during the preparation process the contaminations were removed and do not influence the bio functionality of the surface patterns. The results of the surface analysis carried out with TOF-SIMS were confirmed by complementary cell adhesion experiments with murine fibroblasts. As a result, specific cell adhesion restricted to GRGDS peptide functionalized areas was obvious by the formation of focal adhesion contacts in the fibroblasts. Thus, TOF-SIMS is the method of choice in chemical characterization of surfaces in structuring and functionalization processes, because it offers the opportunity to follow surface contamination during the preparation process and to assess the influence of the contamination on the applicability of the final substrate.  相似文献   

3.
Covalent attachment of adhesive peptides to biomaterials surfaces can result in the formation of a bioactive and biomimetic surface. We have demonstrated that titanium surfaces grafted with adhesion peptides, reproducing sequences of fibronectin and vitronectin, can increase osteoblast adhesion compared to non-treated surfaces.We now extend our investigation to peptide immobilization on glass for studying human osteoblast adhesion and spreading. Silanization was used to anchor adhesion peptides to the glass surface through a selective or a non-selective immobilization. Investigated samples were analysed by XPS spectroscopy. Comparison between the results obtained using two different peptides and applying selective and non-selective immobilization will be discussed.  相似文献   

4.
Patterning of metallic clusters on surfaces is demonstrated by utilizing a buffer layer assisted laser patterning technique (BLALP). This method has been employed in order to measure the diffusion of AFM and STM characterized size selected gold nanoclusters (5-10 nm diameter), over Ru(100) and p(1 x 2)-O/Ru(100) surfaces. Optical linear diffraction from gold cluster coverage gratings was utilized for the macroscopic diffusion measurements. The clusters were found to diffuse on the surface intact without significant coalescence or sintering. The barrier for metastable gold nanocluster diffusion on the surface is thought to be lower than the energy required for surface wetting. The apparent activation energy for diffusion was found to depend on the cluster size, increasing from 6.2 +/- 0.4 kcal/mol for 5 nm clusters to 10.6 +/- 0.5 kcal/mol for 9 nm clusters. The macroscopic diffusion of gold nanoclusters has been studied on the p(1 x 2)-O/Ru(100) surface as well, where surface diffusion was found to be rather insensitive to the clusters size with activation energy of 5.5 +/- 1 kcal/mol. The difference between the two surfaces is discussed in terms of a better commensurability (higher level of friction) of the gold facets at the contact area with the clean Ru(100) than in the case of the oxidized surface.  相似文献   

5.
Coating of artificial surfaces with RGD (= arginine‐glycine‐aspartate) peptides to enhance cell adhesion is an ongoing issue. Thereby, the physiological adhesion process to the extra‐cellular matrix (ECM) is mimicked by the peptide coating, leading to a strong cell‐surface contact, followed by spreading and proliferation of the cells. For comparable cell adhesion studies, it is important to know the density of the RGD peptides on the surface. Here, we present an approach to determine the amount of bound cyclic RGD peptide by radio labeling with 125I of a tyrosine‐containing RGD peptide on different materials surfaces (poly(methyl methacrylate) (PMMA), titanium, and silicon). For all surfaces, the amount of bound peptides is in the range of pmol/cm1.  相似文献   

6.
We report on the self-spreading behavior of a supported lipid bilayer (SLB) on a silicon surface with various 100 nm nanostructures. SLBs have been successfully grown from a small spot of a lipid molecule source both on a flat surface and uneven surfaces with 100 nm up-and-down nanostructures. After an hour, the self-spreading SLB forms a large circle or an ellipse depending on the nanostructure pattern. The results are explained by a model that shows that a single-layer SLB grows along the nanostructured surfaces. The model is further supported by a quantitative analyses of our data. We also discuss the stability of the SLB on nanostructured surfaces in terms of the balance between its bending and adhesion energies.  相似文献   

7.
通过在硅片表面有机蒸镀不同厚度的二十九烷制备了不同晶体密度的仿生旱金莲叶面蜡质纳米结构表面,采用端基修饰多巴的原子力显微镜胶体探针,对各纳米结构表面进行了粘附性能测试,发现蒸镀200 nm厚度二十九烷结晶的纳米结构表面具有较低粘附力。采用反应离子刻蚀方法制备了不同高度的硅材质仿生鲨鱼皮微米结构表面,并选择了200 nm厚度二十九烷在仿生鲨鱼皮表面进行有机蒸镀制备了微纳复合结构表面,通过胶体探针的研究发现多巴与高度为1、3、5μm微纳复合结构表面的粘附力均小于与200 nm厚度二十九烷结晶的纳米结构表面之间的粘附力,说明微纳复合结构表面具有很强的抗多巴粘附能力,并且这种复合结构表面相对于硅材质的仿生鲨鱼皮微米结构表面还兼有旱金莲叶面的强疏水性和极佳的抗水粘附能力。  相似文献   

8.
Using a surface force balance, we have measured the normal and shear forces between mica surfaces across aqueous caesium salt solutions (CsNO(3) and CsCl) up to 100 mM concentrations. In contrast to all other alkali metal ions at these concentrations, we find no evidence of hydration repulsion between the mica surfaces on close approach: the surfaces appear to be largely neutralized by condensation of the Cs ions onto the charged lattice sites, and are attracted on approach into adhesive contact. The contact separation at adhesion indicates that the condensed Cs ions protrude by 0.3 +/- 0.2 nm from each surface, an observation supported both by the relatively weak adhesion energies between the surfaces, and the relatively weak frictional yield stress when they are made to slide past each other. These observations show directly that the hydration shells about the Cs(+) ions are removed as the ions condense into the charged surface lattice. This effect is attributed to the low energies-resulting from their large ionic radius-required for dehydration of these ions.  相似文献   

9.
We report on a modular approach for producing well-defined and electrochemically switchable surfaces on Si(100). The switching of these surfaces is shown to change a Si(100) surface from resistant to cell adsorption to promoting cell adhesion. The electrochemical conversion of the modified electrode surface is demonstrated by X-ray photoelectron spectroscopy, X-ray reflectometry, contact angle and cell adhesion studies.  相似文献   

10.
A new process for surface modification of polymers with multi-source cluster deposition apparatus has been reported in our previous work. The apparatus simultaneously supplies reactant of ammonium sulfamate and activator of energetic Ar(+) ion. In this work chemical changes are analyzed on the basis of XPS spectra and the relations of contact angle and platelet adhesion with chemical changes are discussed. Polymer film, setting on a turning holder, was irradiated by Ar(+) ions during bombardment with ammonium sulfamate clusters. The Ar(+) ion source served for activation of polymer surface and a cluster ion source supplied ammonium sulfamate molecules to react with activated surface. After thorough washing with deionized sterile water, the modified surfaces were evaluated in terms of contact angle of water, elemental composition and binding state on XPS and platelet adhesion with platelet rich plasma (PRP). The modification of polysulfone decreased the contact angle of water on surfaces from 82.6 down to 34.5 degrees. The adhesion number of platelets were decreased to one-tenth of the original surface. Ammonium, amine, sulfate and thiophene combinations were formed on the modified surfaces. The primary studies showed successful modification of polysulfone with ammonium sulfamate by assistance of Ar(+) ion irradiation. The polar groups like N-sulfate were formed on surfaces and contribute to the decrease of surface contact angle and adhesion number of platelets. Since the same process can also be applied to other polymeric materials with various substrates, combining with the features of no solvent and no topographic changes, this method might be developed in a promising way for modification of polymers.  相似文献   

11.
This study examines the adhesion of graphite to functionalized polyester surfaces using a range of qualitative and quantitative measures of theoretical adhesion. Modifications to the polyester surfaces include the addition of hydroxyl, carboxyl, or fluorine substituents with coverages of 0.4 and 0.9 groups per nm(2). In each case, the introduction of substituents to the surface of the polyester was calculated to lead to reduced adhesion to graphite. Effects of surface relaxation on adhesion are studied by employing different simulation protocols. The theoretical results suggest one mechanism to reduce adhesion to carbonaceous solids is to increase atomic roughness using strongly hydrophilic or alternatively strongly hydrophobic substituents.  相似文献   

12.
Antibacterial peptides, magainin I and nisin were covalently bound to stainless steel surfaces. Several procedures of surface functionalisation processes have been investigated and optimized, each step being characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and X-ray photoemission spectroscopy (XPS). Grafting of antibacterial peptides was successfully achieved by a 3 steps functionalisation process on a chitosan polymeric layer. The antibacterial activity of the anchored magainin and nisin was tested against a gram-positive bacteria, Listeria ivanovii, i.e., the possible survival and attachment of this bacteria, was characterized on modified stainless steel surfaces. The results revealed that the adsorbed peptides reduced the adhesion of bacteria on the functionalised stainless steel surface.  相似文献   

13.
The study of the adhesion of lipid vesicles on surfaces is of increasing interest in the field of medical implants and tissue engineering (protein-resistant surfaces), drug delivery, biosensors, and biochips. In this work, lipid coverage was developed from PEG-coated vesicles (with sizes from 100 to 300 nm) by covalently binding poly(ethylene glycol)-alpha-disteroylphosphatidylethanolamine-omega-benzotriazole carbonate (DSPE-PEG-BTC) molecules onto the surface amine groups by carbamate chemistry. Lipid surface density and the surface structure of multilamellar (MLVs) and extruded unilamellar (LUVs) vesicles deposited on three types of polystyrene (PS) well-plates were probed by fluorescence and atomic force microscopy (AFM) imaging. A significant difference in the vesicle surface coverage of PS substrates was observed with a substantial increase in lipid multilayers on the amine-enriched PS surface using both unilamellar and multilamellar vesicles.  相似文献   

14.
Colloid probe atomic force microscopy (CP-AFM) was used to investigate two strains of Burkholderia cepacia in order to determine what molecular scale characteristics of strain Env435 make it less adhesive to surfaces than the parent strain, G4. CP-AFM approach curves analyzed using a gradient force method showed that in a high ionic strength solution (IS=100 mM, Debye length=1 nm), the colloid probe was attracted to the surface of strain G4 at a distance of approximately 30 nm, but it was repelled over a distance of 25 nm when approaching strain Env435. Adhesion forces measured under the same solution conditions during colloid retraction showed that 1.38 nN of force was required to remove the colloid placed in contact with the surface of strain G4, whereas only 0.58 nN was required using strain Env435. At IS=1mM (Debye length=10nm), the attractive force observed with G4 was no longer present, and the repulsive force seen with Env435 was extended to approximately 250 nm. The adhesion of the bacteria to the probe was much less at low IS solution (1 mM) than at high IS (100 mM). The greater adhesion characteristics of strain G4 compared to Env435 were confirmed in column tests. Strain G4 had a collision efficiency of alpha=0.68, while strain Env435 had a much lower collision efficiency of alpha=0.01 (IS=100 mM). These results suggest that the reduced adhesion of strain Env435 measured in column tests is due to the presence of high molecular weight extracellular polymeric substances that extend out from the cell surface, creating long-range steric repulsion between the cell and a surface. Adhesion is reduced as these polymers do not appear to be "sticky" when placed in contact with a surface in AFM tests.  相似文献   

15.
Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2. We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2-coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59 degrees +/-2 to <5 degrees. The water contact angle of the SnO2 surface was reduced only at 254 nm, while contact angle of the Si-m glass surface was not altered by light of either wavelength. Bacterial adhesion decreased by 10-50% to photocatalyzed glass surfaces. In all cases, bacteria exposed to the UV light were completely killed due to a combination of exposure to UV light and the photocatalytic activity of the glass surfaces. These results show that UV light irradiation of TiO2-coated surfaces can be an effective method of reducing bacterial adhesion.  相似文献   

16.
采用电子活化再生原子转移自由基聚合(AGET ATRP)的方法将聚(甲基丙烯酸-2-羟乙酯)(PHEMA)接枝在金表面,对经修饰的金表面的生物惰性做了系统的研究,并利用PHEMA的羟基末端固定生物素(biotin)分子,以biotin对抗生物素蛋白(avidin)的识别为模型,研究了不同厚度的PHEMA对结合avidin的影响,以及该表面作为生物检测基材的可行性.生物惰性研究表明,PHEMA修饰的金表面不但能够有效的排斥纤维蛋白原(Fg)、人血清白蛋白(HSA)和溶菌酶(Lys)的非特异性吸附,还能够抑制3种细胞(L02、L929和EC)的黏附,是一种良好的抗污表面.通过控制聚合时间制备了不同厚度的PHEMA-biotin修饰的表面,同位素125I标记HSA吸附结果表明这几种表面均能够有效排斥非特异性蛋白质吸附,特异性FITC-avidin吸附结果表明,厚度较小时(16 nm)由于荧光淬灭而难以检测到荧光信号,厚度在16 nm和49 nm之间,荧光信号随厚度增加而增强,通过比较信噪比,认为厚度在49 nm以上时比较理想.该表面在应用于QCM与荧光检测中均表现出良好的检测性能.  相似文献   

17.
HSVEC behavior under physiological shear stress in vitro is investigated on PET surfaces micropatterned with both RGDS and WQPPRARI peptides. This technique allows (i) creating geometries on surface to guide cell orientation under shear stress and (ii) controlling surface chemical composition in order to modulate cell behavior. Under shear stress, endothelial cells adhere on patterned PET surfaces and present a more rapid orientation in flow direction in comparison to cells cultured on homogeneous surfaces. Micropatterned surfaces presenting a large surface area ratio of RGDS/WQPPRARI peptides induce fibrillar adhesion, while surfaces presenting an equal RGDS/WQPPRARI peptides surface area ratio preferentially induce focal adhesion.

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18.
Recent advances in dynamic force microscopy show that it is possible to measure the forces between atomically sharp tips and particular atomic positions on surfaces as a function of distance. However, on most ionic surfaces, the positive and negative ions can so far not be distinguished. In this paper, we use the CaF2(111) surface, where atomic resolution force microscopy has allowed identification of the positions of the Ca2+ and F- ions in the obtained images, to demonstrate that short-range interaction forces can be measured selectively above chemically identified surface sites. Combining experimental and theoretical results allows a quantification of the strength and distance dependence of the interaction of a tip-terminating cluster with particular surface ions and reveals details of cluster and surface relaxation. Further development of this approach will provide new insight into mechanisms of chemical bond formation between clusters, cluster deposition at surfaces, processes in adhesion and tribology, and single atom manipulation with the force microscope.  相似文献   

19.
Sun XH  Li CP  Wong NB  Lee CS  Lee ST  Teo BK 《Inorganic chemistry》2002,41(17):4331-4336
The reductive growth of metal clusters on silicon nanowires (SiNWs) is reported. The HF-etched SiNWs were found to reduce ligated Au-Ag clusters of single size, shape, composition, and structure. In the process, the surfaces of the SiNWs were reoxidized. The reductive cluster growth on the SiNW surface was followed by high-resolution transmission electron microscopy (HRTEM). The reduced metal clusters grew to different sizes in the nanometer regime (1-7 nm in diameter) on the SiNW surfaces. At sizes greater than approximately 7 nm, they tend to separate from the SiNW surfaces. Further growth and/or agglomeration of these colloidal particles to sizes greater than roughly 25 nm in diameter eventually causes the particles to precipitate from solution. Two interesting phenomena, the "sinking cluster" and the "cluster fusion" processes, were observed under TEM.  相似文献   

20.
The use of synthetic peptides containing adhesive sequences, such as the Arg-Gly-Asp (RGD) motif, represents a promising strategy to control biological interactions at the cell–material interface. These peptides are known to improve the tissue–material contact owing to highly specific binding to cellular membrane receptors known as integrins, thereby promoting the adhesion, migration and proliferation of cells. The peptides were coupled to borosilicate glass and titanium surfaces using silanisation chemistry. A tryptophan residue was incorporated into the amino acid sequences of selected peptides to facilitate the detection of the covalently bound peptides. Successful peptide immobilisation was proven by fluorimetric measurements. The confocal imaging analysis suggests a homogeneous distribution of the immobilised peptide across the biomaterial surface. In vitro cell proliferation assays were employed to compare the adhesion potentials of the well-known RGD-containing peptides GRGDSP, GRADSP and RGDS to the three peptides designed by our group. The results demonstrate that the RGD sequence is not necessarily required to enhance the adhesion of cells to non-biological surfaces. Moreover, it is shown that the number of adhering cells can be increased by changes in the peptide hydrophobicity. Changes in the cytoskeleton are observed depending on the type of RGD-peptide modification.  相似文献   

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