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T A Horbett

Publications and source records attributed to T A Horbett.

At least 19 recordsLinked to original sources
PubMed1995

Platelet and monoclonal antibody binding to fibrinogen adsorbed on glow-discharge-deposited polymers.

The state of fibrinogen adsorbed on untreated and glow-discharge-treated surfaces was examined by measuring platelet adhesion, monoclonal antibody (mAb) binding, the amount of fibrinogen adsorbed, and the amount of adsorbed fibrinogen which could be eluted with sodium dodecyl sulfate (SDS). Tetrafluoroethylene (TFE) glow-discharge-treated polymers have a lower surface free energy (in air) and retain a larger fraction of adsorbed fibrinogen than untreated surfaces after SDS elution. Platelet adhesion was lowest on the TFE-treated surfaces which retain the highest amounts of fibrinogen after SDS elution. Fibrinogen may undergo unfolding or spreading on the TFE-treated surfaces to minimize interfacial free energy (in water) and maximize protein-surface interactions. When it is adsorbed on the TFE-treated surfaces, fibrinogen evidently assumes a state which somehow prevents its recognition and binding by platelet receptors. Monoclonal antibodies that bind to the three regions in fibrinogen thought to be involved in platelet adhesion were therefore used to detect changes in adsorbed fibrinogen. These regions and the antibodies which bind to them are: the COOH-terminal of the gamma-chain, mAb M1; the RGD peptide sequence at A alpha 95-98, mAb R1; the RGD sequence at A alpha 572-575, mAb R2. For fibrinogen adsorbed on the untreated or TFE-treated surfaces, M1 and R2 binding was relatively high compared to background, while R1 binding was low. However, the amount of binding of each mAb to fibrinogen adsorbed on the TFE-treated surfaces was equal to or greater than fibrinogen adsorbed to the untreated surfaces. Therefore, antibody-detectable changes in the platelet binding regions of adsorbed fibrinogen that might have been caused by conformational or orientational rearrangements were not observed for the TFE-treated surfaces. The data suggest that the tight binding of fibrinogen on a surface may directly affect the ability of the fibrinogen to interact with the platelet receptors--i.e., that fibrinogen must be loosely held to facilitate maximal interaction with platelet receptors.

Adhesiveness↗
PubMed1994

In vitro study of the intrinsic toxicity of synthetic surfaces to cells.

A trypan blue inclusion assay was used to measure cell death on poly(dimethyl siloxane) (PDMS), polyethylene (PE), poly(methyl methacrylate) (PMMA), polyurethanes, glass, and glow-discharge-treated polystyrene or poly(ethylene terephthalate). Cell lines used were bovine aortic endothelial, 3T3, mouse peritoneal macrophage, and BHK cells. In the absence of proteins in the media, PDMS, PE, PMMA, and some polyurethanes were consistently found to induce cell death. This toxic effect disappeared if the cells were seeded in serum-containing medium or if concentrated solutions of proteins (albumin, IgG, or fibronectin) were preadsorbed on the materials. The substrate toxicity appeared to be due to the physical properties of the substrate and not to the release of toxic leachables.

3T3 Cells↗
PubMed1994

Correlation between corneal epithelial cell outgrowth and monoclonal antibody binding to the cell binding domain of adsorbed fibronectin.

The ability of corneal epithelial cells to attach, spread, and migrate on synthetic surfaces is largely determined by the characteristics of the adsorbed protein layer. In previous studies we have described an in vitro model for quantitating epithelial cell outgrowth from explanted corneal buttons onto synthetic materials (Pettit et al., Invest. Ophthalmol. Vis. Sci., 31, 2269 [1990]). We have also described the role of fibronectin (fn) adsorption and binding strength on epithelial cell outgrowth (Pettit et al., J. Biomed. Mater. Res., 26, 1259 [1992]). In the current study we have used a monoclonal antibody against the RGD cell binding domain of fn (mAb 3E3) to further characterize the role of adsorbed fn in promoting epithelial cell outgrowth. Ten materials of diverse chemical and physical properties were adsorbed with fn (0.1 mg/ml) or mixtures of fn and albumin (concentrations totaling 0.1 mg/ml) and tested for antibody recognition of the cell binding domain. The surface density of bound anti-cell binding domain antibody varied from a low of 0.66 +/- 0.11 for fluorinated ethylene propylene copolymer (FEP) to a high of 1.90 +/- 0.26 for tissue culture polystyrene dish substrates (units are OD at 450 nm measured in the ELISA technique normalized to polyethylene). A general increase in cell outgrowth areas was noted, with increases in recognizable cell binding domain. However, several exceptions to this trend were noted as well (e.g., low cell outgrowth but high antibody recognizability for glass). These results suggest that, although the number of cell binding domains exposed on adsorbed fn molecules may influence cell outgrowth, other characteristics of the adsorbed protein, such as the binding strength to the underlying substrate, may be equally important in characterizing epithelial cell-substrate interactions.

Adsorption↗
PubMed1994

Developing correlations between fibrinogen adsorption and surface properties using multivariate statistics. Student Research Award in the Doctoral Degree Candidate Category, 20th annual meeting of the Society for Biomaterials, Boston, MA, April 5-9, 1994.

A multivariate model based on the partial least squares algorithm (PLS) was constructed in order to establish a correlation between the surface properties of common polymeric materials and the amount and retention of fibrinogen absorbed from a complex mixture. Surface characterization was performed by means of static secondary ion mass spectroscopy (SIMS), electron spectroscopy for chemical analysis (ESCA), and by contact angle measurements of several liquids on those materials. 125I-fibrinogen was adsorbed from a 1% plasma solution in buffer and the amount adsorbed after 2 h was determined. After 5 days of residence time in buffer, the adsorbed fibrinogen was eluted with a 1% solution of the surfactant sodium dodecyl sulfate (SDS). The percent of fibrinogen that remained on the surfaces after elution is referred to as fibrinogen retention. Correlations between surface properties and the amounts of fibrinogen adsorbed or fibrinogen retention were established. These models also show the most important variables that are related to the protein behavior on these surfaces.

Adsorption↗
PubMed1994

Residence time effects on monoclonal antibody binding to adsorbed fibrinogen.

Fibrinogen adsorbed to polymeric surfaces and then allowed to reside on the surface while it is kept in a buffer solution for a period of time (the 'residence time') undergoes postadsorptive changes that decrease its SDS elutability, displaceability by plasma, polyclonal antifibrinogen binding, and ability to support platelet adhesion (summarized in Chinn et al. J. Biomed. Mater. Res. 26, 757 (1992)). In order to better understand the nature of the changes in adsorbed fibrinogen, the binding of ten different monoclonal antifibrinogen molecules to fibrinogen adsorbed from plasma to Biomer and several other surfaces has been measured after increasing residence time in buffer. Three of the monoclonal antibodies used bind to sequences that have been implicated in platelet binding to fibrinogen. One of these (M1) binds to the C-terminal region of the gamma chain (402-411), another (R1) binds to the N-terminal region of the A alpha chain containing an RGDF sequence (95-98), and the third (R2) binds to the C-terminal region of the A alpha chain containing an RGDS sequence (572-575). Two other antibodies (P1 and K4) also bind to the C-terminal region of the gamma chain (373-385 and 392-406, respectively). Five other antibodies that bind to other regions in fibrinogen were also used. Two of the antibodies (K4 and P1) are also known to be sensitive to conformational changes in the fibrinogen molecule. The binding of the various antibodies changed with residence time in ways that were highly dependent on the particular antibody. The binding of some antibodies was very stable with respect to residence time, others rose with time, some declined with residence time and one appears to pass through a maximum. However, none of the changes in antibody binding were nearly as fast as has been observed for the changes in platelet binding reported previously. Binding to the platelet binding region near the gamma chain C-terminal region either did not change with residence time (M1), increased with residence time (K4), or else decreased more slowly than observed for platelets (P1). Binding of the antibodies to the RGD sequences near the N-terminus of the A alpha chain (95-98) was very low initially but increased with residence time, while the binding to the RGD sequence near the C-terminus of the A alpha chain (572-575) increased slightly at short residence times but then declined substantially after longer residence times. Thus, the changes in the expression of the putative platelet binding domains do not correlate with the declines in platelet binding to plasma preadsorbed Biomer.(ABSTRACT TRUNCATED AT 400 WORDS)

Adsorption↗
PubMed1992

Platelet adherence and detachment with adsorbed fibrinogen: a flow study with a series of hydroxyethyl methacrylate-ethyl methacrylate copolymers using video microscopy.

The adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) with preadsorbed fibrinogen. Observations of the interactions of acridine-orange-labeled washed platelets with these surfaces from a flowing (500 s-1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). In some cases preadsorbed materials were incubated for 24 h, during which little or no loss of protein occurred. Protein surface concentration, by itself, was a poor indicator of expected cell adhesion and morphology. Surface chemistry was a second important factor which must be considered. A third observation is that for the 100% EMA copolymer, 24 h of incubation led to a large reduction in platelet adhesion when compared to the 100% EMA material without incubation. For the 0% and 100% EMA polymers, the percentage of contacting platelets which adhere and detach is greater for the 24-h incubation cases than for those not incubated. These results led to the conclusion that our most hydrophilic surface favors adhesion with detachment, transient cell contact, over long-term adhesion, as does incubation of adsorbed protein. A brief discussion is presented of a possible connection between this behavior and platelet consumption in vivo for hydrogels.

Adsorption↗
PubMed1992

Glow discharge plasma deposition of tetraethylene glycol dimethyl ether for fouling-resistant biomaterial surfaces.

The glow discharge plasma deposition (GDPD) of tetraethylene glycol dimethyl ether is introduced as a novel method for obtaining surfaces that are resistant to protein adsorption and cellular attachment. Analysis of films by x-ray photoelectron spectroscopy and several biological assays indicate the formation of a fouling-resistant, PEO-like surface on several substrata (e.g., glass, polytetrafluoroethylene, polyethylene). Adsorption of 125I-radiolabelled proteins (fibrinogen, albumin and IgG) from buffer and plasma was very low (typically less than 20 ng/cm2) when compared to the untreated substrata, which exhibited much higher levels of protein adsorption. Not all coated substrata adsorbed equal amounts of protein (e.g., coated glass samples typically adsorbed more protein than coated polyethylene or coated polytetrafluoroethylene samples), suggesting that the substratum used may affect the amount of protein adsorbed. Measurement of dynamic platelet adhesion, using epifluorescent video microscopy, and endothelial cell attachment further demonstrates the short-term nonadhesiveness of these surfaces.

Adsorption↗
PubMed1992

Postadsorptive transitions in fibrinogen adsorbed to polyurethanes: changes in antibody binding and sodium dodecyl sulfate elutability.

Residence time-dependent changes in fibrinogen after adsorption to six different polyurethanes were examined by measuring polyclonal antifibrinogen binding to the adsorbed protein. The amount of adsorbed fibrinogen that could be eluted by sodium dodecyl sulfate (SDS) was also measured. Baboon fibrinogen was first adsorbed from dilute plasma to the polymers, which were then stored in either buffer or buffered albumin solution prior to testing. Subsequently, the amount of antifibrinogen bound by the adsorbed fibrinogen was measured using a direct enzyme linked immunosorbent assay (ELISA). Alternatively, the surface with the adsorbed fibrinogen was soaked in a 3% SDS solution, and the amount of retained 125I-radiolabeled fibrinogen was measured. With increasing residence time, decreases in both antibody binding and the SDS elutability of the adsorbed fibrinogen occurred, but the rate of change was dependent on the polyurethane to which the fibrinogen was adsorbed. In addition, the antibody binding per unit of adsorbed fibrinogen, when measured immediately after the adsorption step, varied by approximately a factor of 3 among the various polyurethanes. When the protein-coated surfaces were stored in buffered albumin solution rather than buffer, the decrease in the reactivity of fibrinogen with residence time did not occur on some of the surfaces. This study shows that the chemical properties of the adsorbing surface influence the rate at which adsorbed fibrinogen undergoes change. The significance of the polymer-dependent changes in adsorbed fibrinogen with respect to blood reactions with polymers is discussed.

Adsorption↗
PubMed1992

Influence of the substrate binding characteristics of fibronectin on corneal epithelial cell outgrowth. Student Research Award in the Doctoral Degree Candidate Category, Fourth World Biomaterials Congress (18th annual meeting of the Society for Biomaterials), Berlin, Germany, April 24-28, 1992.

The outgrowth of corneal epithelial cells onto a polymeric substrate is expected to be the primary event in the epithelialization of a synthetic corneal graft. Circular corneal buttons (5 mm) were punched from excised rabbit corneas and placed onto bare substrates or substrates preadsorbed with fibronectin (fn), albumin, or binary mixtures of both fn and albumin. Cell outgrowth areas were measured after culturing the buttons for 4 days in serum-free medium. Fibronectin adsorption to the materials was measured from pure and binary solutions with 125I-radiolabeled fibronectin. A parameter thought to be related to the binding strength of fn to polymeric substrates was measured in parallel experiments by partial elution of the adsorbed fn by 3% sodium dodecyl sulfate (SDS). Following pure solution fibronectin adsorption a range of outgrowth areas was measured (from 0.86 +/- 0.03 cm2 for glass to 1.49 +/- 0.03 cm2 for TCPS). On all of the materials tested cell outgrowth areas increased following fn preadsorption and decreased following albumin preadsorption relative to bare surfaces (p less than 0.05). Following preadsorption with binary protein mixtures cell outgrowth areas increased with fibronectin adsorption, however, the outgrowth areas were not determined solely by the concentration of fn adsorbed onto the surfaces. This result suggested that the biological efficiency of the adsorbed fibronectin was substrate-dependent. When the cell outgrowth data were cross-plotted against fn retention following SDS elution, the outgrowth areas were found to increase along with increases in fn retention. Based on these data we suggest that epithelial cell outgrowth may be partially governed by the tightness of binding between the fn molecules and the underlying substrate.

Adsorption↗
PubMed1992

Changes in fibrinogen adsorbed to segmented polyurethanes and hydroxyethylmethacrylate-ethylmethacrylate copolymers.

Fibrinogen adsorption from blood to biomaterials may regulate platelet adhesion and thrombus formation because of fibrinogen's central role in the coagulation cascade and its ability to bind specifically to the platelet membrane glycoprotein (GP) IIb-IIIa. Adsorption of fibrinogen from blood plasma to many materials exhibits a maximum with respect to plasma dilution and exposure time (the Vroman effect). In this study fibrinogen adsorption to several polymers was examined to ascertain the influence of controlled changes in surface chemistry on the Vroman effect. The materials included hydroxyethylmethacrylate-ethylmethacrylate (HEMA/EMA) copolymers, Biomer, and a series of segmented polyurethanes (PEUs), two of which contained fluorinated chain extenders. Each material exhibited maximal adsorption of fibrinogen at intermediate plasma concentrations. Little effect of soft-segment type or molecular weight was observed and no significant differences in fibrinogen adsorption to the fluorinated PEUs were seen. Changes in the strength of fibrinogen attachment to these materials with time after adsorption were also assessed. Fibrinogen adsorbed for 1 min was displaced more readily by blood plasma than that adsorbed for 1 h, regardless of the material. The more hydrophobic polymers exhibited greater retention of adsorbed fibrinogen. In addition, the fraction of fibrinogen retained by polyethylene depended on the amount of fibrinogen adsorbed to the surface, being greatest when the surface loading was the least. These studies indicate that spreading or transition of adsorbed fibrinogen molecules from a weakly to tightly bound state is a general consequence of protein adsorption to solid surfaces.

Adsorption↗
PubMed1992

Adsorption of baboon fibrinogen and the adhesion of platelets to a thin film polymer deposited by radio-frequency glow discharge of allylamine.

Platelet adhesion under static and flow conditions from a washed platelet suspension containing albumin to a polymer deposited by radio-frequency glow discharge of allylamine vapour on a poly(ethylene terephthalate) substrate was measured. Electron spectroscopy for chemical analysis was used to characterize the surface. Fibrinogen adsorption from a series of dilute plasma solutions to radio-frequency glow discharge/allylamine, measured using 125I radiolabelled baboon fibrinogen, increased with decreasing plasma dilution to a level much higher than that previously observed on polyurethanes. Elutability by sodium dodecyl sulphate of fibrinogen adsorbed from dilute plasma also increased with increasing plasma concentration, but fibrinogen preadsorbed from plasma became non-elutable when surfaces were stored in buffer for 5 d before contact with sodium dodecyl sulphate. Platelet adhesion to substrates which had been pre-adsorbed with dilute plasma was measured using baboon platelets radiolabelled with 111In. Adhesion greatly decreased as the plasma concentration used for preadsorption increased, suggesting that non-specific platelet binding to the bare surface occurs when protein coverage is incomplete. Non-specific platelet binding was inhibited to varying degrees by preadsorption of different proteins to the surface. Platelet adhesion to surfaces preadsorbed with dilute (1.0%) baboon and human plasmas lacking fibrinogen (i.e. serum, heat-defibrinogenated plasma and congenitally afibrinogenemic plasma) was diminished compared with normal plasma. Addition of exogenous fibrinogen to the deficient plasma partially restored platelet adhesion to normal levels. Adhesion to surfaces preadsorbed with human plasma deficient in von Willebrand factor was comparable to that observed with normal plasma. The plasma preadsorption studies with fibrinogen deficient media suggested that adsorbed fibrinogen is necessary for platelet adhesion to the radio-frequency glow discharge/allylamine substrate at high protein coverage. However, since adhesion was greatly reduced when the plasma preadsorbed substrate was stored in buffer before platelet contact, the conformation of adsorbed fibrinogen is also important in mediating platelet adhesion to radio-frequency glow discharge.

Adsorption↗
PubMed1992

Tight binding of albumin to glow discharge treated polymers.

Tetrafluoroethylene (TFE) glow discharge-treated Dacron vascular grafts resist thrombus deposition, embolization and thrombotic occlusion. In addition, albumin adsorbed on TFE-treated surfaces resists elution by sodium dodecyl sulfate (SDS). Since the tight binding of albumin to TFE-treated surfaces may contribute to their thromboresistant character, we decided to examine the mechanism responsible for this tenacious adsorption. We have investigated albumin adsorption and retention (after SDS elution) on a number of untreated and glow discharge-treated surfaces. Fluorocarbon glow discharge-treated polymers retain a larger fraction of the adsorbed albumin than ethylene and hexamethyldisiloxane glow discharge-treated surfaces. Albumin retention by surfaces appears to be closely related to their surface free energy (in air). Low energy surfaces (in air), whether untreated or glow discharge-treated, retain a larger fraction of the albumin adsorbed than higher energy surfaces. The lowest energy surfaces should have the highest interfacial energies in water, with correspondingly high driving forces for adsorption of proteins. This can lead to the formation of multiple binding sites upon adsorption, permitting strong hydrophobic interactions, which leads to the observed strong binding.

Adsorption↗
PubMed1991

Baboon fibrinogen adsorption and platelet adhesion to polymeric materials.

The role of fibrinogen in mediating platelet adhesion to polymers exposed to blood plasma was studied by comparison of the effect of plasma dilution on fibrinogen adsorption and platelet adhesion, and by the use of coagulation factor deficient plasmas. Polyetherurethane substrates were first preadsorbed with dilute plasma, then contacted with washed platelets suspended in a modified, apyrase containing Tyrode's buffer. Platelet adhesion was studied under static conditions in Multiwell dishes, and also under shearing conditions using a parallel plate perfusion chamber. Fibrinogen adsorption and platelet adhesion were measured using 125I radiolabeled baboon fibrinogen and 111In radiolabeled baboon platelets, respectively. Surfaces were characterized by electron spectroscopy for chemical analysis (ESCA). When fibrinogen adsorption to Biomer was measured after 2 h contact with a series of dilute plasma solutions under static conditions, a peak in adsorption was observed from 0.26% plasma, i.e., adsorption was greater from 0.26% plasma than from either more or less dilute plasma. A peak in subsequent platelet adhesion to the plasma preadsorbed surfaces, measured after 2 h static incubation with washed platelets, was also observed but occurred on Biomer preadsorbed with 1.0% plasma. When fibrinogen adsorption was measured after 5 min contact under shearing conditions, the fibrinogen adsorption peak occurred on surfaces that had been exposed to 1.0% plasma. A peak in platelet adhesion to these preadsorbed surfaces, measured after 5 min contact with the platelet suspensions under shearing conditions, was observed on Biomer preadsorbed with 0.1% plasma. Shifts between the positions of the peaks in protein adsorption and platelet adhesion occurred on other polymers tested as well. Platelet adhesion was almost completely inhibited when baboon and human plasmas lacking fibrinogen (i.e., serum, heat defibrinogenated plasma, and congenitally afibrinogenemic plasma) were used. Platelet adhesion was restored to near normal when exogenous fibrinogen was added to fibrinogen deficient plasmas. Adhesion was also inhibited completely when a monoclonal antibody directed against the glycoprotein IIb/IIIa complex was added to the platelet suspension. Platelet adhesion to surfaces preadsorbed to von Willebrand factor deficient plasma was the same as to surfaces preadsorbed with normal plasma. While it appears that surface bound fibrinogen does mediate the initial attachment of platelets to Biomer, the observation that the fibrinogen adsorption and platelet adhesion maxima do not coincide exactly also suggests that the degree of subsequent platelet adhesion is dictated not only by the amount of surface bound fibrinogen but also by its conformation.

Adsorption↗
PubMed1991

Platelet adherence and detachment: a flow study with a series of hydroxyethyl methacrylate-ethyl methacrylate copolymers using video microscopy.

The adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA). Observations of the interactions of mepacrine labelled washed platelets with these surfaces from a flowing (500 s-1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). Total platelet adhesion, including platelets which adhere on first contact and platelets which attach temporarily before adhesion, and the number of detaching platelets were minimal for the 0 and 20% EMA copolymers, reached a maximum for the 50% EMA copolymer and showed reduced values for the 80% and 100% EMA copolymers. For the 50, 80, and 100% EMA copolymers, the adhesion values expressed, as a percentage of total contacting platelets, were not different. Albumin adsorption to these copolymers shows a continuous increase from the 0% to the 100% EMA copolymer. It is likely that the peak in platelet adhesion at the 50% EMA composition is related to: low protein adsorption on the 0 and 20% EMA copolymers, too little albumin adsorption to block adhesion on the 50% EMA copolymer, and full-scale blocking on the 80 and 100% EMA copolymers due to greater albumin adsorption.

Adult↗
PubMed1991

Postadsorptive transitions in fibrinogen adsorbed to biomer: changes in baboon platelet adhesion, antibody binding, and sodium dodecyl sulfate elutability.

Residence-time-dependent changes in fibrinogen after its adsorption to Biomer were examined by measuring platelet adhesion and antibody binding to the adsorbed protein, and the amount of adsorbed fibrinogen which could be eluted by sodium dodecyl sulfate (SDS). Baboon fibrinogen was first adsorbed (from either pure solution or dilute plasma) to Biomer, which was then stored in either buffer or buffered albumin solution prior to testing. Subsequently, the adherent protein layer was either probed for fibrinogen capable of mediating platelet adhesion using 111In radiolabeled, washed platelet suspensions under both static and shearing conditions, or for fibrinogen capable of binding antibody using a direct enzyme linked immunosorbent assay (ELISA). Alternatively, the surface with the adsorbed protein layer was soaked in a 3% SDS solution, and the amount of 125I radiolabeled fibrinogen retained was measured. Decreases in platelet and antibody binding, and in the SDS elutability of the adsorbed fibrinogen after it was stored in buffer were detected, although different rates of decrease were observed for each method. When the protein-coated surfaces were stored in buffered albumin solution rather than buffer, the decrease in the reactivity of fibrinogen was prevented. While each of the three assays measures a different property of adsorbed fibrinogen, this study suggests that the adherent protein undergoes time dependent conformational changes which render it less reactive toward platelets and antibodies, and more resistant to elution by SDS.

Adsorption↗
PubMed1991

Protein adsorption to poly(ethylene oxide) surfaces.

Surfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted with bis-amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of 125I-labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low-molecular-weight PEO contained many more PEO molecules than the surfaces grafted with higher-molecular-weight PEO. The high-molecular-weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low-molecular-weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of "cooperative" water structuring around the larger PEO molecules may create an "excluded volume" of the hydrated polymer coils. This may be an important factor contributing to the observed low protein adsorption behavior.

Adsorption↗
PubMed1991

The effects of temperature and buffer on fibrinogen adsorption from blood plasma to glass.

[125I]-Fibrinogen was used to measure the adsorption of fibrinogen from baboon plasma to two types of glass (Pyrex and a borosilicate glass) at 25 and 37 degrees C using two different buffers to dilute the plasma, the first being citrate-phosphate buffered saline (CPBSz) and the second isotonic Tris-saline (TRIS), both pH 7.4. In addition, the effects of hydration conditions, rinsing techniques, and glass-cleaning treatments on fibrinogen adsorption were evaluated. The data reveal that lower temperatures and the use of TRIS to dilute the plasma significantly enhance fibrinogen adsorption to both types of glass. As has been observed in the past, fibrinogen adsorption peaked at intermediate plasma concentrations on both Pyrex and borosilicate glass (the so-called Vroman effect), but almost twice as much fibrinogen adsorbed to glass when TRIS was used to dilute the plasma instead of CPBSz. Moreover, up to five times as much fibrinogen adsorbed to both types of glass at 25 degrees C compared with 37 degrees C. No effects of the rinsing technique or glass-cleaning treatment were observed.

Adsorption↗