Effect of Functional Groups of Self-Assembled Monolayers on Protein Adsorption and Initial Cell Adhesion (original) (raw)
Related papers
Rsc Advances, 2013
Due to their ability to confer key functions of the native extracellular matrix (ECM), poly(ethylene glycol) (PEG)-based and PEG-modified materials have been extensively used as biocompatible and biofunctionalized substrate systems to study the influence of environmental parameters on cell adhesion in vitro. Given wide-ranging recent evidence that ECM compliance influences a variety of cell functions, detailed determination and characterization of the specific PEG surface characteristics including topography, stiffness and chemistry is required. Here, we studied two frequently used bio-active interfaces-PEG-based and PEG-modified surfaces-to elucidate the differences between the physical surface properties, which cells can sense and respond to. For this purpose, two sets of surfaces were synthesized: the first set consisted of nanopatterned glass surfaces containing cRGD-functionalized gold nanoparticles surrounded by a passivated PEG-silane layer and the second set consisted of PEG-diacrylate (PEG-DA) hydrogels decorated with cRGD-functionalized gold nanoparticles. Although the two sets of nanostructured materials compared here were highly similar in terms of density and geometrical distribution of the presented bio-ligands, as well as in terms of mechanical bulk properties, the topography and mechanical properties of the surfaces were found to be substantially different and are described in detail. In comparison to the very stiff and ultra-smooth surface properties of the PEG-passivated glasses, the mechanical properties of PEG-DA surfaces in the biologically relevant stiffness range, together with the increased surface roughness at micro-and nanoscale levels have the potential to affect cell behavior. This potential was verified by studying the adhesive behavior of hematopoietic KG-1a and rat embryonic fibroblast (REF52) cells on both surfaces.
Molecules, 2019
In this study, we investigate how a surface structure underneath a surface-attached polymer coating affects the bioactivity of the resulting material. To that end, structured surfaces were fabricated using colloidal lithography (lateral dimensions: 200 nm to 1 µm, height ~15 to 50 nm). The surface structures were further functionalized either with antimicrobial, cell-adhesive polycations or with protein-repellent polyzwitterions. The materials thus obtained were compared to non-functionalized structured surfaces and unstructured polymer monolayers. Their physical properties were studied by contact-angle measurements and atomic force microscopy (AFM). Protein adhesion was studied by surface plasmon resonance spectroscopy, and the antimicrobial activity against Escherichia coli bacteria was tested. The growth of human mucosal gingiva keratinocytes on the materials was analyzed using the Alamar blue assay, optical microscopy, and live-dead staining. The data shows that the underlying s...
Targeted cellular adhesion at biomaterial interfaces
Current Opinion in Solid State & Materials Science, 1998
The interface of biomaterials must be carefully designed to elicit and eliminate specific responses when placed in contact with the body. The interaction of cells with the surfaces of biomaterials is a complex phenomenon that depends on a large number of variables. To design novel biomaterials that possess the desired characteristics, materials scientists and engineers rely heavily upon information provided by molecular biologists. Information regarding cell receptor-ligand interactions is used to understand the role of cellular adhesion in the natural environment so that synthetic biomaterials may be developed successfully. The production of new synthetic materials, understanding how native proteins mediate cellular adhesion with these materials, molecularly engineering surfaces with controlled spatial patterns for optimal responses, evaluation of mechanical properties, and analyzing bioadhesion and surface properties of these materials are topics that must be addressed when discussing targeted cellular adhesion at biomaterial surfaces.
Biomaterials, 2006
The ability of fibronectin (Fn) to mediate cell adhesion through binding to a 5 b 1 integrins is dependent on the conditions of its adsorption to the surface. Using a model system of alkylsilane SAMs with different functional groups (X ¼ OH, COOH, NH 2 and CH 3 ) and an erythroleukemia cell line expressing a single integrin (a 5 b 1 ), the effect of surface properties on the cellular adhesion with adsorbed Fn layers was investigated. 125 I-labeled Fn, a modified biochemical cross-linking/extraction technique and a spinning disc apparatus were combined to quantify the Fn adsorption, integrin binding and adhesion strength, respectively. This methodology allows for a binding equilibrium analysis that more closely reflects cellular adhesion found in stable tissue constructs in vivo. Differences in detachment strength and integrin binding were explained in terms of changes in the adhesion constant (c, related to affinity) and binding efficiency of the adsorbed Fn for the a 5 b 1 integrins (CH 3 ENH 2 oCOOHEOH) and the resulting average bond strength. Fn interacted more strongly with a 5 b 1 integrins when adsorbed on COOH vs. OH surfaces suggesting that negative charge may be a critical component of inducing efficient cellular adhesion. As evident by the low c values, Fn adsorbed on NH 2 and CH 3 surfaces interacted inefficiently with a 5 b 1 integrins and also possessed significant non-specific components to adhesion. Lastly, comparison of cellular adhesion to Fn adsorbed onto smooth and rough surfaces showed that nano-scale roughness altered cellular adhesion by increasing the surface density of adsorbed Fn. r
Biomaterials, 2009
The objective of this study was to compare the biological effects of two key cell-adhesive proteins, fibronectin (FN) and vitronectin (VN), upon adsorption onto molecularly-designed model surfaces. Single-component and mixed self-assembled monolayers (SAMs) of alkanethiols on gold with OH and CH 3 terminal groups were prepared at 100%, 65%, 36% and 0% of OH at the surface, to generate a range of surfaces with a simple chemistry and a wettability gradient. FN and VN were adsorbed under noncompetitive (single-protein solutions) and competitive (multi-protein solutions) conditions, and compared at different levels: adsorbed amount (radiolabelling), elution, functional presentation of cellbinding domains (ELISA), and role in mediating cell adhesion (antibody-based assay). The observed trends were related to mesenchymal stem cell response in terms of adhesion and overall cell morphology. Under non-competitive conditions, adsorption of both proteins increased with surface hydrophobicity. The presence of competitive proteins significantly decreased the adsorbed amounts, although both proteins were still detected in all SAMs. Adsorption of FN followed a trend similar to that of non-competitive conditions, while adsorption of VN was higher on 100%OH-SAMs. Concerning elution, retention of adsorbed VN was always higher than that of FN. For both proteins, functional presentation of cell-binding domains was more effective on the more hydrophilic 100%OH-SAMs. This fact, coupled to the ability of this type of SAMs to selectively recruit and retain VN in the presence of competitive serum proteins, seems to correlate with the better cell response observed on these surfaces, as compared with hydrophobic 0%OH(100%CH 3 )-SAMs.
2006
The ability of fibronectin (Fn) to mediate cell adhesion through binding to a 5 b 1 integrins is dependent on the conditions of its adsorption to the surface. Using a model system of alkylsilane SAMs with different functional groups (X ¼ OH, COOH, NH 2 and CH 3 ) and an erythroleukemia cell line expressing a single integrin (a 5 b 1 ), the effect of surface properties on the cellular adhesion with adsorbed Fn layers was investigated. 125 I-labeled Fn, a modified biochemical cross-linking/extraction technique and a spinning disc apparatus were combined to quantify the Fn adsorption, integrin binding and adhesion strength, respectively. This methodology allows for a binding equilibrium analysis that more closely reflects cellular adhesion found in stable tissue constructs in vivo. Differences in detachment strength and integrin binding were explained in terms of changes in the adhesion constant (c, related to affinity) and binding efficiency of the adsorbed Fn for the a 5 b 1 integrins (CH 3 ENH 2 oCOOHEOH) and the resulting average bond strength. Fn interacted more strongly with a 5 b 1 integrins when adsorbed on COOH vs. OH surfaces suggesting that negative charge may be a critical component of inducing efficient cellular adhesion. As evident by the low c values, Fn adsorbed on NH 2 and CH 3 surfaces interacted inefficiently with a 5 b 1 integrins and also possessed significant non-specific components to adhesion. Lastly, comparison of cellular adhesion to Fn adsorbed onto smooth and rough surfaces showed that nano-scale roughness altered cellular adhesion by increasing the surface density of adsorbed Fn. r
Chemistry of Materials, 2005
A series of copolymers of N-isopropylacrylamide (NIPAM) and the more hydrophobic comonomer N-tert-butylacrylamide (NTBAM), with increasing NTBAM content (i.e., increasing hydrophobicity) were prepared. The adhesion of human epithelial cells on polymer films prepared from copolymers of NIPAM: NTBAM was observed to increase with increasing polymer hydrophobicity. However, in the absence of serum, cell adhesion to the different surfaces was statistically indistinguishable. Thus, it appears that the copolymer films differentially support cell adhesion due to selective adsorption of proteins from the physiological environment (the serum). Using contact angle measurements, molecular simulations, and Raman spectroscopy to characterize the different surfaces, we show evidence that the different behavior of cells on the films of increasing hydrophobicity is actually due to the different chemical properties of the surfaces with increasing content of NTBAM in the copolymers. As the NTBAM content is increased, the number of NH residues at the surface decreases, due to the additional steric hindrance of the bulkier NTBAM group, which results in decreased hydrogen bonding and thus decreased adsorption of proteins such as albumin. However, in some cases, the adsorption is driven by hydrophobic interactions, and proteins such as fibronectin were found to adsorb more to the films with a higher content of NTBAM. There appears, thus, to be a direct correlation between surface composition, i.e., the functional groups exposed at the surface, and protein binding and subsequent cell adhesion.
The quantification of single cell adhesion on functionalized surfaces for cell sheet engineering
Biomaterials, 2010
The use of force spectroscopy to measure and quantify the forces involved in the adhesion of 3T3 fibroblasts to different chemically functionalized surfaces has been investigated. Cells were grown on glass surfaces as well as on surfaces used for cell sheet engineering: surfaces coated with polyelectrolyte multilayers (poly-L-lysine and hyaluronic acid) and thermally-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes. Individual adherent cells were detached from their culture substrate using an AFM cantilever coated with fibronectin. The maximum forces of detachment of each cell were measured and taken as characteristic of the cellular adhesion. Large differences in cellular adhesion were observed on polyelectrolyte coatings depending on the number of polyelectrolyte layers. On PNIPAM-grafted surfaces, changes of more than an order of magnitude were observed in cell adhesion above and below the lower critical solution temperature. Glass surfaces patterned with periodic PNIPAM microdomains were also investigated, and it was shown that cellular adhesion could be reduced while keeping cellular morphology unchanged.
Effect of Preadsorbed Proteins on Cell Adhesion to Polymer Surfaces
Journal of Colloid and Interface Science, 1993
Adsorption of three different proteins and adhesion of cells onto various substrates in the presence of serum proteins were studied. Both the maximal protein adsorption and the maximal cell adhesion were observed on surfaces with water contact angle around 70°. Preadsorption of serum albumin prevented cell adhesion to all the substrates, whereas preadsorbed fibronectin (FN) enhanced cell adhesion to all the substrates, independent of their water wettability, except for poly(vinyl alcohol) and acrylamide-grafted films. Competitive adsorption of FN from mixed proteins, ranging from 0.03 to 0.07 p.g/cm2 , markedly influenced cell adhesion in the presence of serum. These results suggest that the effect of the water wettability of surfaces on cell adhesion in the presence of serum should occur through protein layers adsorbed directly to the substrate surfaces. ©1993 Academic Press, inc.
The effect of non-specific interactions on cellular adhesion using model surfaces
2005
The contribution of non-specific interactions between cells and model functional surfaces was measured using a spinning disc apparatus. These model functional surfaces were created using self-assembled monolayers (SAM) of alkylsilanes terminated with epoxide, carboxyl (COOH), amine (NH 2 ), and methyl (CH 3 ) groups. These SAMs were characterized using ellipsometry, atomic force microscopy, contact angle goniometry, and X-ray photoelectron spectroscopy to confirm the presence of well-formed monolayers of expected physicochemical characteristics. All substrates also demonstrated excellent stability under prolonged exposure (up to 18 h) to aqueous conditions. The adhesion strength of K100 erythroleukemia cells to the functional substrates followed the trend: CH 3 o COOH E epoxide { NH 2 . The NH 2 SAM surface exhibited nearly an order of magnitude greater adhesion strength than the other SAMs and this non-specific effect exceeded the adhesion measured when RGD tri-peptides were also immobilized on the surface. These findings illustrate the importance of substrate selection in quantitative studies of peptidemediated cellular adhesion. r