|Articles about Biomaterials|
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| Adhesion and aggregation of thrombin prestimulated human platelets: evaluation of a series of biomaterials characterized by ESCA
Feuerstein, I. A. and B. D. Ratner (1990), Biomaterials 11(2): 127-32.
Abstract: Five materials of interest in blood contact applications (PVC, Silastic, Biomer and siliconized glass) were internally coated on glass tubes and exposed to suspensions of platelets and red cells. Uncoated glass was also examined. Thrombin was added (prestimulation) to some suspensions before exposure to the biomaterial surfaces. The three polymeric surfaces were characterized by electron spectroscopy for chemical analysis (ESCA). Prestimulation with thrombin leads to increased adhesion of single platelets only with Silastic. With a wide range of surface types, thrombin prestimulation consistently leads to higher levels of platelet accumulation in the form of aggregates; the PVC-coated material showed the highest levels. ESCA analysis of PVC, however, suggested our coating was impure or an oxidized material.
| Adhesion and morphology of fibroblastic cells cultured on different polymeric biomaterials
Lombello, C. B., A. R. Santos, Jr., et al. (2002), J Mater Sci Mater Med 13(9): 867-74.
Abstract: Cell adhesion is influenced by the physical and chemical characteristics of the materials used as substrate for cell culturing. In this work, we evaluated the influence of the morphological and chemical characteristics of different polymeric substrates on the adhesion and morphology of fibroblastic cells. Cell growth on poly (L-lactic acid) [PLLA] membranes and poly(2-hydroxy ethyl methacrylate) [polyHEMA], poly(2-hydroxy ethyl methacrylate)-cellulose acetate [polyHEMA-CA] and poly(2-hydroxy ethyl methacrylate)-poly(methyl methacrylate-co-acrylic acid) [polyHEMA-poly(MMA-co-AA)] hydrogels of different densities and pore diameters was examined. Cells adhered preferentially to more negatively charged substrates, with polyHEMA hydrogels being more adhesive than the other substractes. The pores present in PLLA membranes did not interfere with adhesion, but the cells showed a distinctive morphology on each membrane.
| Adhesion and proliferation of cells on new polymers modified biomaterials
Lakard, S., G. Herlem, et al. (2004), Bioelectrochemistry 62(1): 19-27.
Abstract: Up to today, several techniques have been used to maintain cells in culture for studying many aspects of cell biology and physiology. More often, cell culture is dependent on proper anchorage of cells to the growth surface. Poly-l-lysine is commonly used as adhesive molecule. In this study, we present, as an alternative to poly-l-lysine, new polymer film substrates, realized by electropolymerization of different monomers on fluorine-doped tin oxide (FTO) surfaces since electropolymerization is a good method to coat selectively metallic or semiconducting electrodes with polymer films. So, the adhesion, proliferation and morphology of rat neuronal cell lines were investigated on polymer treated surfaces. Several amine-based biocompatible polymers were tested: polyethyleneimine (PEI), polypropyleneimine (PPI), polypyrrole (PPy) and poly(p-phenylenediamine) (PPPD). These polymer films were coated on FTO surfaces by electrochemical oxidation. After 8 h in a culture medium, a high percentage of cells was found to be attached to PEI and PPI compared to the other polymers and to the reference surfaces (glass and FTO uncovered). After 24 and 72 h in the culture medium, cells were found to proliferate faster on PEI and PPI than on other polymers and reference surfaces. Consequently, cells have a greater fold expansion on PEI and PPI than on PPPD, PPy or glass and FTO uncoated. From these results, we deduce that PEI and PPI can be useful as coating surface to cultivate neuronal cells.
| Adhesion contact dynamics of 3T3 fibroblasts on poly (lactide-co-glycolide acid) surface modified by photochemical immobilization of biomacromolecules
Zhu, A. P., N. Fang, et al. (2005), Biomaterials
Abstract: A simple and effective method of biomacromolecule immobilization on biomaterial surface for direct tuning of biophysical parameters such as the initial cell deformation rate, degree of cell spreading and adhesion kinetics is important for tissue engineering. The photochemical immobilization of azide-chitosan (Az-CS) on poly (lactide-co-glycolide) acid (PLGA) is applied here. Chitosan immobilization on PLGA through the photoactive azide group further facilitates subsequent grafting of other biocompatible biomacromolecules like gelatin (Gel) through the active amine groups on CS. This study quantitatively compares the 3T3 fibroblast adhesion dynamics on three PLGA surfaces (Gel-CS-PLGA, CS-PLGA and unmodified PLGA surfaces) using Confocal-Reflectance Interference Contrast Microscopy (C-RICM) together with phase contrast imaging. CS-PLGA and Gel-CS-PLGA surfaces developed were confirmed by X-ray photoelectron spectroscopy, atomic force microscopy and water contact angle and cell adhesion contact dynamics measurements. The cell adhesion was strongest on the Gel-CS-PLGA surface and lowest on unmodified PLGA. The steady state adhesion energy attained by the cells on gelatin modified PLGA surface is determined as 4.0x10(-8)J/m(2), which is about 400 times higher than that on PLGA surface (1.1x10(-10)J/m(2)). Significantly increased cell adhesion with Gel-CS-PLGA is postulated to result in increased cell spreading. Our integrated biophysical method can quantify the transient contact dynamics and is sufficiently accurate to discriminate even between Gel and CS modified surfaces.
| Adhesion contact dynamics of fibroblasts on biomacromolecular surfaces
Fang, N., A. Zhu, et al. (2005), Macromol Biosci 5(10): 1022-31.
Abstract: Biomacromolecules like gelatin and chitosan have emerged as highly versatile biomimetic coatings for applications in tissue engineering. The elucidation of the interfacial kinetics of cell adhesion on biomacromolecular surfaces will pave the way for the rational design of chitosan/gelatin-based systems for cell regeneration. Biomacromolecular ultra-thin films, chemically immobilized on fused silica are ideal experimental models for determining the effect of surface properties on the biophysical cascades following cell seeding. In this study, confocal reflectance interference contrast microscopy (C-RICM), in conjunction with phase contrast microscopy and fluorescence confocal microscopy, was applied to detect the adhesion contact dynamics of 3T3 fibroblasts on chitosan and gelatin ultrathin films. X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of chitosan or gelatin on the silanized glass surface. Both the initial cell deformation rate and the change of two-dimensional spread area of the 3T3 fibroblasts are higher on gelatin-modified surfaces than on chitosan surfaces. The steady-state adhesion energy of 3T3 fibroblasts on gelatin film is three times higher than that on chitosan film. Immuno-staining of actin further demonstrates the different organization of cytoskeleton, likely induced by the change in cell signaling mechanism on the two biomacromolecular surfaces. The better attachment of 3T3 fibroblast to gelatin is postulated to be caused by the presence of adhesive domains on gelatin.
| Adhesion dynamics, morphology, and organization of 3T3 fibroblast on chitosan and its derivative: the effect of O-carboxymethylation
Zhu, A. P. and N. Fang (2005), Biomacromolecules 6(5): 2607-14.
Abstract: Chitosan and O-carboxymethylchitosan (OCMCS) have been proved to have biocompatibility and have been extensively researched in the field of biomaterials. In this study, Confocal-reflectance interference contrast microscopy (C-RICM) in conjunction with phase contrast imaging was used to investigate the adhesion contact dynamics of 3T3 fibroblasts on chitoan and OCMCS surface-modified silica coverslips. The C-RICM results demonstrate that the weak cell contact forms on OCMCS surface while a much stronger contact area forms on the chitosan surface. 3T3 fibroblasts are found to spread randomly with spindlelike morphology on the chitosan surface, while they exhibit elongated morphology and align on the OCMCS surface. It is believed that fibroblast behaviors such as migration, spreading with an elongated morphology, and alignment on the OCMCS surface are correlated with the weak cell contact. The mechanisms to form cell adhesion contact on chitosan and OCMCS were discussed.
| Adhesion of a Staphylococcus aureus strain to biomaterials does not select methicillin-resistant mutants
Montanaro, L., D. Cavedagna, et al. (2001), New Microbiol 24(1): 57-61.
Abstract: Bacterial adhesion to polymethylmethacrylate and to silicon elastomer, materials frequently used in clinical applications, has been investigated to assess whether adhesion selects methicillin-resistant mutants in the bacterial population in contact with the materials. The methicillin susceptibility of a susceptible Staphylococcus aureus (ATCC 25923) was measured by a modification of plate antibiogram Kirby-Bauer method, which allows optimised detection of small variations in antibiotic susceptibility. In both adherent and non-adherent bacterial subpopulations, the presence of mecA gene, which encodes for the protein PBP 2a responsible for methicillin resistance was searched for by Polymerase Chain Reaction (PCR). The contact with the two polymers did not induce in the bacteria population any phenotypic increase in methicillin resistance, or the selection of mutants carrying the mecA gene.
| Adhesion of coagulase-negative staphylococci to biomaterials
Hogt, A. H., J. Dankert, et al. (1983), J Gen Microbiol 129(9): 2959-68.
Abstract: The adhesion of two Staphylococcus epidermidis strains and one Staphylococcus saprophyticus strain on to poly(tetrafluorethylene-co-hexafluorpropylene) (FEP)-fluorocarbon and cellulose acetate was studied in vitro. Both S. epidermidis strains showed a more hydrophobic character than the encapsulated S. saprophyticus as determined by the bacterial affinity towards xylene. Staphylococcus epidermidis showed a significantly higher adhesion on to the hydrophobic FEP than S. saprophyticus. The adhesion of staphylococci on to the more hydrophilic cellulose acetate was always low. Treatment of S. epidermidis with pepsin or extraction with aqueous phenol yielded cells with a decreased hydrophobicity, which resulted in a decreased adhesion on to FEP. Cells with a decreased hydrophobicity showed a lower rate of reaggregation in suspension. The hydrophobicity and the adhesion on the FEP of S. epidermidis were not affected by exposure to a subminimal inhibitory concentration of penicillin. The strong interaction between S. epidermidis and FEP, which appeared not to be influenced by the age or the metabolic stage of the bacteria, is mainly caused by hydrophobic bonding.
| Adhesion of human leukocytes to biomaterials: an in vitro study using alkanethiolate monolayers with different chemically functionalized surfaces
Barbosa, J. N., M. A. Barbosa, et al. (2003), J Biomed Mater Res A 65(4): 429-34.
Abstract: The adhesion of human leukocytes to self-assembled monolayers of well-defined surface chemistry was investigated in vitro. Polymorphonuclear (PMN) and mononuclear leukocytes were isolated from human blood by centrifugation techniques. The effect on adhesion of cell activation produced by pre-incubation of leukocytes with phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) was also studied. Gold substrates were modified by treatment with alkanethiols with three different terminal chemical groups: COOH, OH, and CH(3). After incubation with the two subpopulations of leukocytes, the monolayers were washed, treated with fixative, stained with a Giemsa method, and observed by light microscopy to quantify the number of attached leukocytes. Comparative quantification of the density of leukocyte adhesion to the three types of self-assembled monolayers was determined. The hydrophobic surface expressing CH(3) was found to be the one that induced the highest adhesion density of leukocytes, both of PMN and mononuclear cells. In vitro activation of both mononuclear and PMN leukocytes further increased cell adhesion to the chemically defined monolayers that were used. This enhancement was higher for PHA-activated than for PMA-stimulated mononuclear cells, whereas PMA treatment of neutrophils resulted in a higher rate of adhesion of these cells than PHA stimulation.
| Adhesion of human peripheral lymphocytes on biomaterials preadsorbed with fibronectin and vitronectin
Groth, T., I. Zlatanov, et al. (1994), J Biomater Sci Polym Ed 6(8): 729-39.
Abstract: The adhesion of human peripheral lymphocytes (HPL) was studied after preadsorption of fibronectin (FN) and vitronectin (VN) on hydrophilic glass and hydrophobic octadecyl glass. The adhesion of HPL was shown to be dependent not only on the wettability but also on the protein preadsorbed. Vitronectin expressed not only a higher extent of adhesion under static conditions but also a stronger interaction with HPL, indicated by the low detachment under shear stress. The flow experiments also demonstrated that FN adsorbed on octadecyl glass may undergo conformational changes because HPL could be easily removed. Scanning electron microscopy revealed that HPL on both FN- and VN-coated glass spread well whereas particularly on FN-coated octadecyl glass less cell spreading was observed; moreover, some round cells were detected. The typing of adherent HPL by immunofluorescence microscopy showed that on FN- and VN-coated glass about 70% of all HPL were T-cells (CD 3+). However, on octadecyl glass, particularly on VN, a smaller percentage of CD 3+ cell was observed. The testing for the beta 1 integrin--the receptor for FN and the alpha v integrin--the receptor for VN demonstrated that about 70% of all cells on FN-coated glass were positive for the beta 1 integrin. On VN-coated glass, however, only 5% of HPL were positive for the beta 1 integrin. Although on VN a high adhesion and strong binding of HPL was observed, no presence of the alpha v integrin was detected.
| Adhesion of Pseudomonas aeruginosa to collagen biomaterials: effect of amikacin and ciprofloxacin on the colonization and survival of the adherent organisms
Trafny, E. A., K. Kowalska, et al. (1998), J Biomed Mater Res 41(4): 593-9.
Abstract: The adherence of P. aeruginosa to collagen membrane, sponge, and to a new anti-infective COLL dressing and the susceptibility of the organisms attached to the biomaterials to amikacin were investigated in vitro. After 17 h of attachment, the bacteria demonstrated an increased resistance to amikacin compared with their free-floating counterparts. Amikacin, even at a concentration exceeding 150 times the minimal bactericidal concentration (MBC) for the strain tested, did not eradicate the attached bacteria from the surface of collagen membrane. However, when the drug at a high concentration (over 16 times the minimal inhibitory concentration, MIC) was present in the incubation medium before it had been inoculated with P. aeruginosa, a reduction of 2 log10 units in the organisms adherent to the surface of collagen membrane was observed. We conclude that slow release of the antibiotic from the COLL dressing could control the bacterial colonization on the surface. In fact, the released amikacin at the final concentration of 32 times the MBC reduced the number of adherent bacteria by 6 log10 units. In contrast, ciprofloxacin at the same final bactericidal concentration completely eradicated the bacteria from the surface of COLL dressing. However, as ciprofloxacin is not recommended for use as a topical antimicrobial agent, a further search is needed to find an agent with a similar anticolonization activity.
| Adhesion of Staphylococcus epidermidis and Staphylococcus saprophyticus to a hydrophobic biomaterial
Hogt, A. H., J. Dankert, et al. (1985), J Gen Microbiol 131(9): 2485-91.
Abstract: The relative surface charge and hydrophobicity of 16 strains of Staphylococcus epidermidis showed large variations. For this species no relationship between the two surface parameters was found. A highly negative surface charge was observed in all seven encapsulated strains (one S. epidermidis and six Staphylococcus saprophyticus strains). The adhesion of the staphylococci to fluorinated polyethylene-propylene films was not related to the relative surface charge and the hydrophobicity of the bacteria. On films pre-exposed to human plasma, the bacterial adhesion was substantially reduced. Mechanisms involved in the adhesion of coagulase-negative staphylococci to this biomaterial are discussed.
| Adhesion strength of human tenocytes to extracellular matrix component-modified poly(DL-lactide-co-glycolide) substrates
Qin, T. W., Z. M. Yang, et al. (2005), Biomaterials 26(33): 6635-42.
Abstract: We report a direct measurement of the adhesion strength of human embryonic tenocytes (HETCs) and transformed human embryonic tenocytes (THETCs) to fibronectin (FN)- and type I collagen (CNI)- modified poly(DL-lactide-co-glycolide) (PLGA) substrates with a micropipette aspiration technique. PLGA substrates were first coated with poly-D-lysine (PDL), and then with various concentrations (1 microg/ml, 2 microg/ml, 5 microg/ml, and 10 microg/ml) of FN and CNI in serum-free F12 media. Anti-FN and Anti-CNI antibodies were used to inhibit attachment of tenocytes to FN- and CNI- modified substrates in a dilution range of 1:5000-1:500 and 1:1500-1:250, respectively. The substrates were employed for incubation of HETCs and THETCs for 30 min at 37 degrees C before the adhesion strength measurements. We found that the adhesion strengths showed a strong dependence on the seeding time and FN or CNI concentrations. Anti-FN and Anti-CNI antibodies significantly compromised adhesion of HETCs and THETCs to the corresponding modified substrates (P < 0.05). These findings show that FN- or CNI-modified polymer substrates offer significant advantages for tissue engineering tendon scaffolds concerning tenocyte adhesion. In addition, HETCs and THETCs bear similar biological behaviors in terms of adhesion, indicating the possibility of using THETCs in place of HETCs in tissue engineering construction of human tendons.
| Adhesion to a polymeric biomaterial affects the antibiotic resistance of Staphylococcus epidermidis
Arciola, C. R., M. E. Donati, et al. (2001), New Microbiol 24(1): 63-8.
Abstract: The antibiotic-resistance both of adherent bacteria to polymethylmethacrylate (PMMA) and of bacteria which, although exposed to the material, had not undergone adhesion, was measured as bacterial growth inhibition area onto a plate antibiogram, according to Kirby-Bauer and using a dedicated image analyzer system. The adhesion onto PMMA induces a marked (about 30%) increase in resistance to beta-lactam antibiotics (cefamandole, cefazolin, imipenem and ampicillin) and a lower (about 15%) but significant increase to the macrolide erythromycin, to two aminoglycosides (amikacin, netilmicin) and to vancomycin, chloramphenicol and trimethoprim-sulfamethoxazole.
| Adhesion, spreading, and aggregation of platelets in flowing blood and the reliability of the retention test Homburg
Krischek, B., E. Morgenstern, et al. (2005), Semin Thromb Hemost 31(4): 449-57.
Abstract: Adhesion and aggregation are important parameters characterizing the function of intact platelets in flowing blood and in contact with a more or less thrombogenic surface. In the retention test Homburg (RTH), platelets are exposed to a standardized textured surface (Sysmex retention tubes) under defined conditions of flow. Platelet counts are performed before and after the Sysmex retention tube passage. The difference between these values indicates the percentage of retained platelets (retention index). Decreased retention in the RTH indicates a loss of function or defective platelet function; increase is associated with an increased activation of platelets, for example, in patients with vascular diseases. For further evaluation of the retention phenomenon the filters were fixed after cell passage and examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM micrographs show activated platelets adhering and spreading on the filter surface, comparable with platelets on a disturbed endothelium. Also, we examined the influence of different G forces and centrifugation times on the retention behavior of the platelets in citrated platelet-rich plasma (PRP) and whole blood (WB). G forces influenced the retention index in PRP and WB significantly and in a different way. Finally, we used a platelet standard, as customary in the quality check, to determine the serial as well as the day-to-day precision.
| Adhesion-mediated signal transduction in human articular chondrocytes: the influence of biomaterial chemistry and tenascin-C
Mahmood, T. A., R. de Jong, et al. (2004), Exp Cell Res 301(2): 179-88.
Abstract: Chondrocyte 'dedifferentiation' involves the switching of the cell phenotype to one that no longer secretes extracellular matrix found in normal cartilage and occurs frequently during chondrocyte expansion in culture. It is also characterized by the differential expression of receptors and intracellular proteins that are involved in signal transduction pathways, including those associated with cell shape and actin microfilament organization. The objective of this study was to examine the modulation of chondrocyte phenotype by cultivation on polymer substrates containing poly(ethylene glycol) (PEG). We observed differential arrangement of actin organization in articular chondrocytes, depending on PEG length. When cultivated on 300 g/mol PEG substrates at day 19, chondrocytes had lost intracellular markers characteristic of the differentiated phenotype, including type II collagen and protein kinase C (PKC). On these surfaces, chondrocytes also expressed focal adhesion and signaling proteins indicative of cell attachment, spreading, and FA turnover, including RhoA, focal adhesion kinase, and vinculin. The switch to a dedifferentiated chondrocyte phenotype correlated with integrin expression. Conversely, the expression of CD44 receptors coincided with chondrogenic characteristics, suggesting that binding via these receptors could play a role in maintaining the differentiated phenotype on such substrates. These effects can be similar to those of compounds that interfere in intracellular signaling pathways and can be utilized to engineer cellular response.
| Adhesive colonization of biomaterials and antibiotic resistance
Gristina, A. G., C. D. Hobgood, et al. (1987), Biomaterials 8(6): 423-6.
Abstract: This study addresses the problem of antibiotic resistance in adhesive, biomaterial-centred infections. It is suggested that this anionic, extracapsular, polysaccharide slime produced by bacteria protects them from antibiotics and sequesters critical ions from the surface of biomaterials. Biofilm-enclosed bacteria on the surface of stainless steel substrata in a test chamber were challenged with incremental levels of tobramycin. In this setting, the minimum inhibitory concentration and minimum bactericidal level of tobramycin for Staphylococcus epidermis were well above normal.
| Adipose tissue engineering using mesenchymal stem cells attached to injectable PLGA spheres
Choi, Y. S., S. N. Park, et al. (2005), Biomaterials 26(29): 5855-63.
Abstract: The reconstruction of soft tissue defects remains a challenge in plastic and reconstructive surgery, and a real clinical need exists for an adequate solution. This study was undertaken in order to differentiate mesenchymal stem cells (MSCs) into adipocytes, and to then assess the possibility of constructing adipose tissue via the attachment of MSCs to injectable PLGA spheres. We also designed injectable PLGA spheres for scar-free transplantation. In this study, MSCs and adipo-MSCs (MSCs cultured in adipogenic medium for 7 days) were attached to PLGA spheres and cultured for 7 days, followed by injection into nude mice for 2 weeks. As a result, the difference between lipid accumulation in adipo-MSCs at 1 and 7 days was much higher in vitro than in the MSCs. Two weeks after injection, a massive amount of new tissue was formed in the APLGA group, whereas only a small amount was formed in the MPLGA group. We verified that the newly formed tissue originated from the injected MSCs via GFP testing, and confirmed that the created tissue was actual adipose tissue by oil red O staining and Western blot (PPAR(gamma) and C/EBP(alpha) were expressed only in APLGA groups). Therefore, this study presents an efficient model of adipose tissue engineering using MSCs and injectable PLGA spheres.
| Adjunctive effect of a polylactide/polyglycolide copolymer in the treatment of deep periodontal intra-osseous defects: a randomized clinical trial
Minenna, L., F. Herrero, et al. (2005), J Clin Periodontol 32(5): 456-61.
Abstract: AIM: The aim of this study was to evaluate the clinical outcome of re-constructive surgery in human deep intra-osseous defects with the use of a polylactide/polyglycolide (PLA/PGA) copolymer graft in conjunction with an open flap debridement (OFD) procedure (test group) as compared with OFD procedure alone (control group). MATERIALS AND METHODS: Thirty-two patients, each contributing one defect, were selected and completed the 12-month follow-up period. Sixteen patients (eight males, mean age: 49.9 years) received the test treatment, 16 patients (nine males, mean age: 42.8 years) received the control treatment. Clinical recordings, assessed at baseline, 6 and 12 months post-surgery, included defect-specific plaque score, defect-specific bleeding score, probing depth (PD), clinical attachment level (CAL), and recession depth. Surgical procedure aimed to preserve supra-crestal soft tissues at defect site in order to ensure primary closure was used in all cases. RESULTS: Test and control treatment produced a significant CAL decrease and PD reduction at both 6 and 12 months with respect to baseline value (p<0.000). At 6 months CAL was significantly greater in test compared with control group (p=0.019). Twelve-month CAL gain was 3.6+/-1.5 and 3.4+/-1.4 mm for the test and control group, respectively. At 12 months no significant differences in any of the clinical parameters were observed between groups. CONCLUSION: The results indicate that OFD with and without PLA/PGA graft provide clinically and statistically significant improvements in PD and CAL measurements. However, the additional use of PLA/PGA did not provide an additional benefit in terms of CAL gain and PD reduction compared with OFD procedure.
| Adsorbed layers of oriented fibronectin: a strategy to control cell-surface interactions
Calonder, C., H. W. Matthew, et al. (2005), J Biomed Mater Res A 75(2): 316-23.
Abstract: Fibronectin (Fn) is a matrix protein known to induce cell attachment and spreading through its cell binding site and related synergy sites. Fn-coated surfaces are therefore useful in tissue engineering and other cell contacting applications, but a problem with many immobilization strategies is a random distribution of molecular orientations. We sought to control Fn orientation, and thus enhance the availability of its cell binding site, by immobilizing Fn via a carboxymethyl dextran layer onto which are chemically attached monoclonal antibodies specific to a region near to Fn's C terminus (and thus away from the cell binding site). Using optical waveguide lightmode spectroscopy, we show the presence of chemically coupled antibodies to yield a considerably denser and thicker Fn layer, consistent with a more vertically aligned protein. Human umbilical vein endothelial cells spread significantly faster, and in a more spherically symmetric way, on an oriented Fn layer (i.e., in the presence of immobilized monoclonal antibodies) as compared with a control Fn layer (i.e., in the absence of bound antibodies). However, we observe human umbilical vein endothelial cell spreading on the oriented Fn layer to be similar to that on a Fn layer in the absence of a carboxymethyl dextran layer, suggesting that although orienting Fn is a promising strategy, coupling strategies using linkers other than dextran may be needed.
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