Surfaces that resist bioadhesion

The search for surfaces that resist bioadhesion has continued with the pursuit of a number of avenues. A large part of the studies has investigated PEG coatings. Nevertheless, there is still controversy about what exactly the properties and modes of action of an ‘ideal’ PEG coating should be. While some studies have reported no irreversible protein adsorption, other, very similar coatings appear less able to resist bioadhesion. Of great interest are results showing that PEG surfaces with very short chains are capable of rejecting proteins. As it is very difficult to obtain direct information about the microstructure of the coatings, studies typically employ plausible models to interpret observations. New analytical techniques and the direct measurement of interfacial forces between proteins and surfaces open up the possibility of improved, guided design and feedback in the optimization of surfaces intended to resist bioadhesion.     

Linear and Hyperbranched Polyglycerol Derivatives as Excellent Bioinert Glass Coating Materials

The non‐specific adsorption of proteins to surfaces in contact with biofluids constitutes a major problem in the biomedical and biotechnological field, due to the initiation of biofilm formation and the resulting improper function of devices. Therefore, non‐fouling surfaces modified with poly(ethylene glycol) (PEG) are usually applied. In this study, we report the synthesis of triethoxysilane modified glycerol based polymers of linear and branched architecture for the preparation of covalently attached monolayers on glass. Evaluation of the biocompatibility of these surfaces was performed in comparison to bare non‐coated glass, hydrophobic hexadecane modified glass, and mPEG modified glass as the controls. Protein adsorption of BSA and fibrinogen (1 mg · mL^?1 in PBS) after 4 and 24 h immersion was reduced by more than 96 and 90%, respectively, compared to the adsorption on bare glass substrates. In addition, mouse NIH‐3T3 fibroblast cells showed only marginal adhesion on the polyglycerol and mPEG coated slides after 3 and 7 d incubation in cell suspension, which demonstrates the long‐term stability of the applied glass coatings. The non‐adhesive properties of these coatings were further reflected in bacterial adhesion tests of Escherichia coli K12 and three clinically relevant Gram‐positive and negative strains (Staphylococcus aureus, Pseudomonas aeruginosa, and Aeromonas hydrophila), since linear polyglycerol (LPG(OH)), linear poly(methyl glycerol) (LPG(OMe)), and hyperbranched polyglycerol (HPG) reduced the adhesion for all tested strains by more than 99% compared to bare glass. Therefore, polyglycerol derivatives present an excellent non‐fouling surface coating as an alternative to PEG with feasibility for surface modification of various substrates.     

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.     

Characterization of poly(L-lysine)-graft-poly(ethylene glycol) assembled monolayers on niobium pentoxide substrates using time-of-flight secondary ion mass spectrometry and multivariate analysis

Control of protein adsorption onto solid surfaces is a critical area of biomaterials and biosensors research. Application of high performance surface analysis techniques to these problems can improve the rational design and understanding of coatings that control protein adsorption. We have used static time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate several poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) adlayers adsorbed electrostatically onto negatively charged niobium pentoxide (Nb(2)O(5)) substrates. By varying the PEG graft ratio (i.e., the number of lysine monomers per grafted PEG chain) and the molecular weights of the PLL and PEG polymers, the amount of protein adsorption can be tailored between 1 and 300 ng/cm(2). Detailed multivariate analysis using principal component analysis (PCA) of the positive and negative ion TOF-SIMS spectra showed changes in the outermost surface of the polymer films that were related to the density and molecular weight of the PEG chains on the surface. However, no significant differences were noted due to PLL molecular weight, despite observed differences in the serum adsorption characteristics for adlayers of PLL-g-PEG polymers with different PLL molecular weights. From the PCA results, multivariate peak intensity ratios were developed that correlated with the thickness of the adlayer and the enrichment of the PEG chains and the methoxy terminus of the PEG chains at the outermost surface of the adlayer. Furthermore, partial least squares regression was used to correlate the TOF-SIMS spectra with the amount of protein adsorption, resulting in a predictive model for determining the amount of protein adsorption on the basis of the TOF-SIMS spectra. The accuracy of the prediction of the amount of serum adsorption depended on the molecular weight of the PLL and PEG polymers and the PEG graft ratio. The combination of multivariate analysis and static TOF-SIMS provides detailed information on the surface chemistry and insight into the mechanism for protein resistance of the coatings.     

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.     

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.     

Sterilization effects on starPEG coated polymer surfaces: characterization and cell viability

Sterilization is frequently an issue for polymeric biomaterials including hydrogels, where autoclaving needs to be discarded, and γ-irradiation and low temperature hydrogen peroxide gas plasma sterilization are already important alternatives. Coatings based on poly(ethylene glycol) are a well-known strategy to reduce unspecific protein interactions on biomaterial surfaces. Dense, ultrathin coatings of isocyanate terminated star-shaped poly(ethylene glycol) (starPEG) molecules have proven to be resistant to unspecific adsorption of proteins and enable direct biofunctionalization. The effectivity and stability of the starPEG coatings on poly(vinylidene fluoride) (PVDF) were studied after γ-irradiation (normed dosis 25 kGy) and plasma sterilization (Sterrad 100S). The selected surface properties determined were: surface composition (X-ray photoelectron spectroscopy, XPS), wettability (sessile drop contact angle) and protein adsorption by fluorescence microscopy (Avidin-TexasRed, Bovine Serum Albumin-Rhodamin). Preliminary cell experiments with the cell line L929 were performed prior and after sterilization to investigate the cell repellence of the starPEG coatings as well as cell viability and specific cell adhesion on GRGDS-modified coatings. The starPEG coating undergoes a slight oxidation due to plasma and γ-sterilization; this represents a minor variation confirmed by XPS and contact angle results. The non-sterilized starPEG and the plasma-sterilized coatings are protein repellent, however the protein adsorption on starPEG coated substrates is much stronger after γ-sterilization for both avidin and bovine serum albumin. The cell experiments indicate that the starPEG coatings are appliable homogeneously by incubation and are non-cell adherent. Moreover, after both sterilization processes the starPEG coatings remain cell repellent and the GRGDS-modified coatings presented vital cells. Thus we conclude that the plasma sterilization is more convenient for the starPEG coatings and GRGDS-modified starPEG coatings.     

A facile method for construction of antifouling surfaces by self-assembled polymeric monolayers of PEG-silane copolymers formed in aqueous medium

Self-assembled polymeric monolayers (PMs) on Si/SiO2 wafers were prepared in water from a series of random copolymers of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSMA), denoted as poly(TMSMA-r-PEGMA). Four polymers of poly(TMSMA-r-PEGMA) were synthesized by free radical polymerization with a systematic variation of co-monomer feed ratios. Regardless of PEG grafting density in the copolymers, all PMs formed approximately 1 nm-thick film as measured by ellipsometry. However, the PMs with a higher grafting density of PEG resulted in more hydrophilic surfaces in terms of water contact angle. The protein resistance of the PMs was evaluated using bovine serum albumin (BSA) as a model protein. Analyses by ellipsometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) showed that the PMs of the copolymers markedly reduced the nonspecific adsorption of proteins compared to the unmodified Si/SiO2 wafers. The study also revealed that the PMs prepared from the copolymers with a higher PEG grafting density were more effective in resisting the nonspecific protein adsorption.     

Preparation and characterization of cross-linked phospholipid bilayer capillary coatings for protein separations

Analysis of protein and peptide mixtures via capillary electrophoresis is hindered by nonspecific adsorption of analytes to the capillary walls, resulting in poor separations and quantitative reproducibility. Phospholipid bilayer (PLB) coatings are very promising for improving protein and peptide separations due to the native resistance to nonspecific protein adsorption offered by PLBs; however, these coatings display limited chemical and temporal stability. Here, we show the preparation and characterization of a highly cross-linked, polymerized phospholipid capillary coating prepared using bis-SorbPC. Poly(bis-SorbPC) PLB coatings are prepared in situ within fully enclosed fused silica capillaries via self-assembly and radical polymerization. Polymerization of the PLB coating stabilizes the membrane against desorption from the surface and migration in an electric field, improves the temporal and chemical stability, and allows for the separation of both cationic and anionic proteins, while preserving the native resistance to nonspecific protein adsorption of natural PLBs.     

Stable permanently hydrophilic protein-resistant thin-film coatings on poly(dimethylsiloxane) substrates by electrostatic self-assembly and chemical cross-linking

Poly(dimethylsiloxane) (PDMS) is a biomaterial that presents serious surface instability characterized by hydrophobicity recovery. Permanently hydrophilic PDMS surfaces were created using electrostatic self-assembly of polyethyleneimine and poly(acrylic acid) on top of a hydrolyzed poly(styrene-alt-maleic anhydride) base layer adsorbed on PDMS. Cross-linking of the polyelectrolyte multilayers (PEMS) by carbodiimide coupling and covalent attachment of poly(ethylene glycol) (PEG) chains to the PEMS produced stable, hydrophilic, protein-resistant coatings, which resisted hydrophobicity recovery in air. Attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed that the thin films had excellent chemical stability and resisted hydrophobicity recovery in air over 77 days of measurement. The spectra also showed a dense coverage for PEG dialdehyde and excellent resistance to protein adsorption from undiluted rat serum. Atomic force microscopy revealed dense coverage with PEG dialdehyde and PEG diamine. Contact angle measurements showed that all films were hydrophilic and that the PEG dialdehyde-topped thin film had a virtually constant contact angle (approximately 20 degrees ) over the five months of the study. Electrokinetic analysis of the coatings in microchannels always exposed to air also gave good protein separation and constant electroosmotic flow during the five months that the measurements were done. We expect that the stable, hydrophilic, protein-resistant thin-film coatings will be useful for many applications that require long-term surface stability.     

Incorporation of bovine serum albumin into biomimetic coatings on titanium with high loading efficacy and its release behavior

Bovine serum albumin (BSA) was employed as a model protein to study its loading efficiency into a calcium phosphate (CaP) coating on titanium substrates. It is found that the protein loading efficiency can be adjusted by varying the specific configurations of the coating system such as simulated body fluid (SBF) volume, solution height and container selection for the SBF. A BSA loading efficiency as high as 90% was achieved when the ratio of the substrate surface area to modified SBF (m-SBF) volume was as high as 0.072. The release of BSA from the biomimetic coatings was also investigated in vitro. A sustained release was achieved although a large quantity of BSA was still trapped in the coating after 15 days of immersion in a phosphate buffer solution. A much faster release rate would be expected when the coating is implanted in vivo due to the active involvement of osteoclast cells and enzymes.     

Amyloid-Like Protein Aggregates: A New Class of Bioinspired Materials Merging an Interfacial Anchor with Antifouling

Surfaces that resist nonspecific protein adsorption in a complex biological milieu are required for a variety of applications. However, few strategies can achieve a robust antifouling coating on a surface in an easy and reliable way, regardless of material type, morphology, and shape. Herein, the preparation of an antifouling coating by one-step aqueous supramolecular assembly of bovine serum albumin (BSA) is reported. Based on fast amyloid-like protein aggregation through the rapid reduction of the intramolecular disulfide bonds of BSA by tris(2-carboxyethyl)phosphine, a dense proteinaceous nanofilm with controllable thickness (≈130 nm) can be covered on virtually arbitrary material surfaces in tens of minutes by a simple dipping or spraying. The nanofilm shows strong stability and adhesion with the underlying substrate, exhibiting excellent resistance to the nonspecific adsorption of a broad-spectrum of contaminants including proteins, serum, cell lysate, cells, and microbes, etc. In vitro and in vivo experiments show that the nanofilm can prevent the adhesion of microorganisms and the formation of biofilm. Compared with native BSA, the proteinaceous nanofilm coating exposes a variety of functional groups on the surface, which have more-stable adhesion with the surface and can maintain the antifouling in harsh conditions including under ultrasound, surfactants, organic solvents, and enzymatic digestion.     

Surface Coating‐Dependent Cytotoxicity and Degradation of Graphene Derivatives: Towards the Design of Non‐Toxic,Degradable Nano‐Graphene

With the increasing interests of using graphene and its derivatives in the area of biomedicine, the systematic evaluation of their potential risks and impacts to biological systems is becoming critically important. In this work, we carefully study how surface coatings affect the cytotoxicity and extracellular biodegradation behaviors of graphene oxide (GO) and its derivatives. Although naked GO could induce significant toxicity to macrophages, coating those two‐dimensional nanomaterials with biocompatible macromolecules such as polyethylene glycol (PEG) or bovine serum albumin (BSA) could greatly attenuate their toxicity, as independently evidenced by several different assay approaches. On the other hand, although GO can be gradually degraded through enzyme induced oxidization by horseradish peroxidase (HRP), both PEG and BSA coated GO or reduced GO (RGO) are rather resistant to HRP‐induced biodegradation. In order to obtain biocompatible functionalized GO that can still undergo enzymatic degradation, we conjugate PEG to GO via a cleavable disulfide bond, obtaining GO‐SS‐PEG with negligible toxicity and considerable degradability, promising for further biomedical applications.     

壳聚糖与羧甲基壳聚糖蛋白质印迹聚合物的制备及吸附性能

首先制备了壳聚糖的衍生物——羧甲基壳聚糖,再以壳聚糖与羧甲基壳聚糖的共混物为功能单体,牛血清白蛋白(BSA)为模板蛋白质,制备了一种壳聚糖与羧甲基壳聚糖共混物的蛋白质印迹聚合物。模板蛋白质吸附测试结果表明,该蛋白质印迹聚合物对BSA的吸附量是非印迹聚合物的30.8倍;对不同蛋白质的吸附测试结果表明,相比于其它对比蛋白质,该蛋白质印迹聚合物具有良好的选择性吸附模板蛋白质BSA的效果;并且该蛋白质印迹聚合物具有良好的可重复使用性能。     

Glow discharge plasma-induced immobilization of heparin and insulin on polyethylene terephthalate film surfaces enhances anti-thrombogenic properties

Polyethylene terephthalate (PET) films were treated with DC glow discharge plasma followed by graft copolymerization with acrylic acid (AA) and polyethylene glycol (PEG). The obtained PET–PEG was coupled to heparin or insulin molecules. The surfaces were then characterized by contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surface energies of the modified PET films were estimated using contact angle measurements, and the changes in crystallinity of the plasma-modified PET film surfaces were investigated by X-ray diffraction (XRD) analysis. The blood compatibilities of the surface-modified PETs were examined by in vitro thrombus formation, whole blood clotting time, platelet contact and protein adsorption experiments. The results revealed that the contact angle value decreased and that the interfacial tension between the modified PET films and blood protein was drastically diminished compared to unmodified PET film. The XPS results showed that the PET–AA surface containing carboxylic acid and the immobilized PET surface containing both carboxylic acid and amino groups exhibited a hydrophilic character, and AFM results showed marked morphological changes after grafting of AA, PEG and biomolecule immobilization. Heparin and insulin-coupled PET surfaces exhibited much less platelet adhesion and protein adsorption than the other surface-modified PET film surfaces.     

In situ comparative studies of self-assembly adsorption of bovine serum albumin on nano films by atomic force microscopy

The self-assembly adsorption of function protein on crystal surfaces, as a common phenomenon, broadly takes place in many applications of biosensors, biocapsules and bioMEMS/bioNEMS. To systematically investigate the different adsorption characteristic of the same function protein on two different crystal surfaces under the identical environment, a hybrid surface composing silica and discontinuous Gold Nano Film (GNF) was fabricated by Physical Vapor Deposition (PVD) and ultrasonic cleaning method, where the dynamic process of the self-assembly adsorption of Bovine Serum Albumin (BSA) was in situ observed by Atomic Force Microscope (AFM). The variations on the junction area of the two different surfaces were studied in the aqueous solution before and after injecting BSA with 0.05 mg/ml concentration. It was found that silica, compared with same hydrophilic GNF, took on a fairly weak adsorption force. The results indicated that the adsorption strength of BSA on the hydrophilic crystal surface was determined not only by hydrophilic property, but also other interaction forces, like Van der Waals and so on. Moreover, observed under the contact mode of AFM, BSA adsorbed on GNF had great tendency to forming a ridge-like topography. These results may be helpful in the application of immunosensors and other areas.     

Probing Adsorption Behaviors of BSA onto Chiral Surfaces of Nanoparticles

Chiral properties of nanoscale materials are of importance as they dominate interactions with proteins in physiological environments; however, they have rarely been investigated. In this study, a systematic investigation is conducted for the adsorption behaviors of bovine serum albumin (BSA) onto the chiral surfaces of gold nanoparticles (AuNPs), involving multiple techniques and molecular dynamic (MD) simulation. The adsorption of BSA onto both L‐ and D‐chiral surfaces of AuNPs shows discernible differences involving thermodynamics, adsorption orientation, exposed charges, and affinity. As a powerful supplement, MD simulation provides a molecular‐level understanding of protein adsorption onto nanochiral surfaces. Salt bridge interaction is proposed as a major driving force at protein–nanochiral interface interaction. The spatial distribution features of functional groups (? COO^?, ? NH₃⁺, and ? CH₃) of chiral molecules on the nanosurface play a key role in the formation and location of salt bridges, which determine the BSA adsorption orientation and binding strength to chiral surfaces. Sequentially, BSA corona coated on nanochiral surfaces affects their uptake by cells. The results enhance the understanding of protein corona, which are important for biological effects of nanochirality in living organisms.     

Protein-repellent silicon nitride surfaces: UV-induced formation of oligoethylene oxide monolayers

The grafting of polymers and oligomers of ethylene oxide onto surfaces is widely used to prevent nonspecific adsorption of biological material on sensors and membrane surfaces. In this report, we show for the first time the robust covalent attachment of short oligoethylene oxide-terminated alkenes (CH(3)O(CH(2)CH(2)O)(3)(CH(2))(11)-(CH═CH(2)) [EO(3)] and CH(3)O(CH(2)CH(2)O)(6)(CH(2))(11)-(CH═CH(2)) [EO(6)]) from the reaction of alkenes onto silicon-rich silicon nitride surfaces at room temperature using UV light. Reflectometry is used to monitor in situ the nonspecific adsorption of bovine serum albumin (BSA) and fibrinogen (FIB) onto oligoethylene oxide coated silicon-rich silicon nitride surfaces (EO(n)-Si(x)N(4), x > 3) in comparison with plasma-oxidized silicon-rich silicon nitride surfaces (SiO(y)-Si(x)N(4)) and hexadecane-coated Si(x)N(4) surfaces (C(16)-Si(x)N(4)). A significant reduction in protein adsorption on EO(n)-Si(x)N(4) surfaces was achieved, adsorption onto EO(3)-Si(x)N(4) and EO(6)-Si(x)N(4) were 0.22 mg m(-2) and 0.08 mg m(-2), respectively. The performance of the obtained EO(3) and EO(6) layers is comparable to those of similar, highly protein-repellent monolayers formed on gold and silver surfaces. EO(6)-Si(x)N(4) surfaces prevented significantly the adsorption of BSA (0.08 mg m(-2)). Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity and static water contact angle measurements were employed to characterize the modified surfaces. In addition, the stability of EO(6)-Si(x)N(4) surfaces in phosphate-buffered saline solution (PBS) and alkaline condition (pH 10) was studied. Prolonged exposure of the surfaces to PBS solution for 1 week or alkaline condition for 2 h resulted in only minor degradation of the ethylene oxide moieties and no oxidation of the Si(x)N(4) substrates was observed. Highly stable antifouling coatings on Si(x)N(4) surfaces significantly broaden the application potential of silicon nitride-coated microdevices, and in particular of microfabricated filtration membranes.     

聚醚砜微孔膜对牛血清蛋白吸附性能的研究

主要研究了聚醚砜(PES)微孔膜对牛血清蛋白(BSA)的吸附性能.用BCA(bicinchoninincacid)法测定了膜孔中吸附的蛋白量.运用扫描电子显微镜和电子单纱强力仪分别对PES膜结构和力学性能进行表征.随着聚乙二醇20000(PEG20000)与聚乙二醇400(PEG400)比值的增大牛血清蛋白的吸附量先减小后增大,水通量先增大后减小,截留率始终维持在97.93%～99.39%之间,结果表明,PEG20000与PEG400比例为2时PES膜的亲水性最好,对BSA的吸附量最小.     

Effectiveness of admixtures,surface treatments and antimicrobial compounds against biogenic sulfuric acid corrosion of concrete

In situ failure of laboratory tested coatings against biogenic sulfuric acid (BSA) corrosion of concrete in sewers has lead to new approaches that affect microbial activity. This paper reports on the performance of concrete surfaces containing antimicrobial polymer fibers or metal-zeolites in preventing BSA corrosion. Additionally, the effectiveness of commercial surface treatments and admixtures was measured by means of accelerated chemical exposure and microbiological simulation tests. The biocidal effect of antimicrobial additives was quantified by means of incubation tests on mortar specimens. The presence of antimicrobial compounds resulted in a 3–12-fold decrease of the bacterial activity, as observed from ATP measurements. The largest deterioration from the accelerated tests was noticed for a cementitious coating. The antimicrobial and silicates admixtures did not result in a protective effect towards degradation under the given test conditions. The best protection was obtained with a polyurea lining and an epoxy coating. No loss of coating integrity could be observed after 8 and 10 cycles of microbiological and chemical testing, respectively.