Kinetics fibrinogen adsorption

The time course of fibrinogen adsorption onto the two types of poly-(HEMA) is depicted in Figure 3 which also includes representative points for poly (HEMA) grafted onto Silastic. The slow rise to the final adsorption level seen for both types of poly (HEMA) is very similar to the kinetics observed for grafted poly (HEMA), as is the actual amount of adsorption. The slight disparity between the poly (HEMA) types is probably related to the more open and thus rougher surface of the heterogeneous poly (HEMA). 

The Kinetics of Baboon Fibrinogen Adsorption to Polymers In vitro and in vivo Studies... 

Figure 4 Kinetics of adsorption of fibrinogen from plasma to glass at various plasma concentrations (indicated on curves). Reproduced with permission from Ref 44. Copyright 1984, F.K. Schattauer-Verlag.

Thus, for the 4 polyalkyl methacrylates tested, the kinetics of fibrinogen adsorption differed for fibrinogen solution, whole plasma and diluted plasma. However for each one of these three media, fibrinogen adsorption to each of the four methacrylates did not differ significantly. The measured amounts of adsorbed fibrinogen did not, therefore, correlate with the platelet reactivity of the polymers, as previously assayed in polymer-coated bead columns. 

Welin-Klinstroem et al used a null ellipsometer equipped with an automatic sample scanning device for studies of adsorption and desorption of fibrinogen and IgG at the liquid/solid interface on surface wettability gradients on silicon wafers. To follow the processes along the wettability gradient, off-null ellipsometry was used. The kinetics of adsorption and nonionic-surfactant-induced desorption varied considerably between fibrinogen and IgG. In the hydrophilic region, veiy little protein desorption was seen when a nonionic surfactant was used. 

These kinetics studies required development of reproducible criteria of subtraction of foe H-O-H bending band of water, which completely overlaps foe Amide I (1650 cm 1) and Amide II (1550 cm"1) bands (98). In addition, correction of foe kinetic spectra of adsorbed protein layers for foe presence of "bulk" unadsorbed protein was described (99). Examination of kinetic spectra from an experiment involving a mixture of fibrinogen and albumin showed that a stable protein layer was formed on foe IRE surface, based on foe intensity of the Amide II band. Subsequent replacement of adsorbed albumin by fibrinogen followed, as monitored by foe intensity ratio of bands near 1300 cm"1 (albumin) and 1250 cm"1 (fibrinogen) (93). In addition to foe total amount of protein present at an interface, foe possible perturbation of foe secondary structure of foe protein upon adsorption is of interest. Deconvolution of foe broad Amide I,II, and m bands can provide information about foe relative amounts of a helices and f) sheet contents of aqueous protein solutions. Perturbation of foe secondary structures of several well characterized proteins were correlated with foe changes in foe deconvoluted spectra. Combining information from foe Amide I and m (1250 cm"1) bands is necessary for evaluation of protein secondary structure in solution (100). 

Wertz CF, Santore MM (1999) Adsorption and relaxation kinetics of albumin and fibrinogen on hydrophobic surfaces single-species and competitive behavior. Langmuir 15(26) 8884-8894... 

The size of a molecule is an important feature because proteins form multiple contacts with the surface (e.g., 77 contact points in the case of the albumin molecule and 703 contact points in the case of the fibrinogen molecule adsorbed on silica [10]). Multipoint binding usually causes adsorption irreversibility having a dynamic nature in the absence of irreversible denaturation. The rates of desorption are, as a rule, much lower than those of adsorption, and in many cases it is virtually impossible to attain the equilibrium state desorbing the adsorbed protein [11]. In other words, the formation of one or several bonds with the surface increases the probability of adsorption of neighboring sites of the same molecule. On the other hand, the desorption of a protein molecule requires the simultaneous rupture of a large number of bonds and, for kinetic reasons, equilibrium is not attained [12-14], This corresponds to a considerable difference between the activation energies for the adsorption and desorption processes [15,16],... 

If the intensities of various infrared bands are measured and plotted against time of flow, the kinetics or rate of adsorption can be determined. This is only true if infrared bands that are not sensitive to conformation or structural changes are used the intensity will then be related directly to the total amount of adsorbed material. The two bands that were common to all proteins studied, and that were independent of conformational changes at constant pH are the bands at 1550 cm-1 (Amide II) and 1400 cm-1. These bands are shown for the fibrinogen-albumin mixture in Figure 11, where... 

The present paper focuses on results obtained recently on equilibrium and kinetic properties of macromolecular adsorption, at vairious "model" interfaces. We have worked mainly on polyacrylamide as an example of a flexible, water-soluble polymer, and on albumin and fibrinogen as typical plasma proteins. For a number of... 

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. 

Brash and ten Hove (27) have shown that the early plasma protein adsorption and desorption events occur more slowly and can be more readily examined if the plasma is diluted. Using this approach, we found that exposure of each of the methacrylate polymers to 1% plasma (Fig. 4C) resulted in fibrinogen binding which showed maxima after 1 to 3 minutes of exposure followed by decreases in bound fibrinogen to an apparent plateau at less than 0.1 ug/cm. These kinetics are similar to those reported by Brash and ten Hove i2J) for glass, siliconized glass and polyethylene. 

Figure 4. Adsorption kinetics for fibrinogen from 0.6% plasma.

The hf(t) curves (Figure 6.35) describing the adsorption kinetics of the HSAi-Fgn and Fgi-HSAn pairs (see also adsorption rate constants in Figure 6.37) are essentially different in respect to the effect of the second protein. For the pair HSA,-Fgn, the relaxation effect is absent for the second protein. In contrast, for Eg,-HSA, the hfi) valne increases then decreases to practically full relaxation, as the graphs show the same rate of decrease before and after the/minimum (Figure 6.33). The decrease in the h t) valne is dne to the albnmin desorption but fibrinogen is not desorbed. 

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