Plasma fibrinogen adsorption from

Slack SM, Horbett TA (1988) Physicochemical and biochemical aspects of fibrinogen adsorption from plasma and binary protein solutions onto polyethylene and glass. J Colloids Interf Sci 124(2) 535-551... 

Fibrinogen Adsorption from Plasma. Films were submerged in 2 ml of O.OIM HEPES, 0.I47M NaCl, 0.02% azide, pH 7.4. Eight ml of citrated plasma (pH 7.6) containing I-fibrinogen was added, and the solutions were mixed by swirling the films. 

Fibrinogen adsorption from plasma was found to be maximal at intermediate plasma concentrations, and was considerably lower from 70-100% plasma or from 0.01% plasma than from 0.1 or 1% plasma, an observation called the Vroman effect. 

ELISA and I-labelling of proteins have been seen to give results in case of fibrinogen adsorption from plasma onto glass and different copolymers. ... 

Fibrinogen adsorption from citrated blood plasma onto Silastic, poly-(HEMA)/Silastic and poly (NVP)/Silastic have been measured twice with two separate plasma preparations made from the blood of separate... 

Fibrinogen adsorption from citrated blood plasma was in the order Silastic < poly(HEMA)/Silastic < poly(NVP)/Silastic. The different order from buffer adsorption may be due to lipoprotein adsorption from plasma to Silastic. 

Figure 2.25 Fibrinogen and antithrombin (AT) adsorption from plasma (2h). PEO MW= 1000 Da. Data are means SD, n=4. AT adsorption on PEO-OH-ATH and PEO-COOH-ATH is significantly greater than that on all other surfaces (P<0.05). Reprinted with permission from Ref. [137].

Chen et al. utUized a direct chemical reaction with a given solution (wet treatment) to modify the surface of the silicone rubber. The presence of a layer of PEO on a biomaterial surface is accompanied by reductions in protein adsorption, and cell and bacterial adhesion. In order to obtain a PEO layer on top of the silicone rabber surface, the surface was firstly modihed by incorporating an Si-H bond using (MeHSiO) , and followed by PEO grafting to the surface using a platinum-catalyzed hydrosilylation reaction. These PEO-modified surfaces were demonstrated by fibrinogen adsorption both from buffer and plasma, as well as albumin adsorption from buffer. Reductions in protein adsorption of as much as 90% were noted on these surfaces. 

The adsorption experiments were carried out by quantifying each of proteins adsorbed on the material from mono-component protein solutions, from four-component protein solutions, and from plasma and diluted plasma. Adsorption profiles of protein were largely different, depending on the aforementioned experimental conditions. For instance, the behavior of any particular protein from diluted plasma varied in response to the extent of plasma dilution. Cooper s results are illustrated in Fig. 3, on fibrinogen adsorption onto five polymer surfaces. It is seen that the adsorption profiles are different one another, being influenced by the different nature of the polymer surfaces. The surface concentrations of adsorbed protein are mostly time-dependent, and maxima in the adsorption profiles were observed. This is interpreted in terms of replacement of adsorbed fibrinogen molecules by other proteins later in time (Vroman effect). Corresponding profiles were also presented for FN and VN. 

Price, M. E., Cornelius, R. M., and Brash, J. L. (2001), Protein adsorption to polyethylene glycol modified liposomes from fibrinogen solution and from plasma, Biochim. Biophys. Acta, 1512,191-205. 

Table V shows that the amount of adsorption onto Silastic from plasma is significantly depressed below its saturation value measured in buflFer presumably because of competition from other components of the plasma. The diflFerence in adsorption from the two plasma pools may result from the increased fibrinogen concentration in one pool which would allow more eflFective competition for adsorption onto Silastic and result in enhanced adsorption. Since the adsorption of fibrinogen onto poly (HEMA)/Silastic from plasma is not so greatly depressed relative to adsorption from buflFer (see Table V), an increase in plasma fibrinogen concentration might not have so large an eflFect on adsorption onto poly-(HEMA)/Silastic as it apparently does on adsorption onto Silastic itself.

In any case, it is clear that the main findings in the two plasma experiments are the same fibrinogen adsorption onto Silastic from plasma is less than onto poly (HEMA)/Silastic, which is the reverse of the situation for adsorption from buffer, as Table V shows. These results thus lead to the conclusion that other plasma constituents are very effective competitors for fibrinogen adsorption onto Silastic while adsorption of fibrinogen onto poly (HEMA)/Silastic from plasma and buffer is quantitatively and qualitatively much more similar. 

The reduced adsorption of fibrinogen from plasma onto Silastic and poly (HEMA)/Silastic compared with that from pure buffered saline solutions could be caused by competition from other proteins for the adsorption sites. Albumin and y-globulin are both present in plasma in relatively high concentrations (about 45 and 10 mg/ml, respectively, compared with ca. 3 mg/ml for fibrinogen), so either might compete effectively with fibrinogen for adsorption. To test this, mixtures of I-fibrinogen... 

Fig 4. Fibrinogen adsorption c n plasma vs platelet adhesion from blood to protein coated glass for 13 minutes exposure at lOOOS-1 shear. 

A concerted effort is presently needed to study the mechanisms influencing adsorption behavior in protein mixtures. Does adsorption from mixtures behave as the sum of independent adsorption events determined by specific affinity constants charactertistic of each species Can such a simple explanation suffice to explain the peak in adsorption isotherms seen for fibrinogen from plasma ("the Vroman effect") and also from binary mixtures (56,57) If the differences in adsorption behavior of mixtures compared to single adsorbates are better understood than at present, a greater degree of control of the adsorption process to achieve a desired end (e.g., selection of a desired protein) may be possible. For example, if the Vroman effect is a general feature of all protein mixtures, then clearly there is an optimum concentration for adsorption to achieve the greatest selectivity. 

Albumin and Y 9 obulin vs. fibrinogen competition in binary mixtures indicated that these proteins may be quantitatively dominant factors in modifying surface adsorption of fibrinogen from plasma. 

The adsorption kinetics of fibrinogen to polymers from blood in vivo stnd from plasma in vitro and the consumption of platelets in vi vo induced by the polymers, all vary with polymer polarity. 

---