Poly fibrinogen adsorption

A study has been carried out on the interactions of blood with plasticised poly(vinyl chloride) biomaterials in a tubular form. The influence of different factors such as the biomaterial, antithrombotic agent, blood condition and the nature of the application is represented when considering the blood response in the clinical utilisation of the plasticised PVC. The PVC was plasticised with di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TEHTM)and in-vitro and ex-vivo procedures used to study the biomaterial with respect to the selection of the plasticiser. The blood response was measured in terms of the measurement of fibrinogen adsorption capacity, thrombin-antithrombin III complex and the complement component C3a. X-ray photoelectron spectroscopy was used for surface characterisation of the polymers and the data obtained indicated that in comparison with DEHP-PVC, there is a higher reactivity... 

Figure 3. Fibrinogen adsorption onto ungrafted poly(HEMA). The poly-(HEMA) sheets [and grafted poly(HEMA)/Silastic were equilibrated at 37°C in 1 mg/ml fibrinogen solution in O.OIM HEPES, 0J47M NaCl, 0.02% azide, pH 7.4 for the time depicted and then rinsed 60 sec with buffer at room temperature by the dilution displacement technique (see Methods).

The poly (HEM A) sheets were prepared by B. Ratner using a special technique he developed. The HEMA solutions were poured between glass plates, and polymerization was chemically initiated. The chemical and physical properties of this material are very similar to those of radiation-grafted poly (HEMA) insofar as protein adsorption is concerned. Heterogeneous or homogeneous poly (HEMA) films were made by polymerization in solvents in which the poly (HEMA) is insoluble or soluble, respectively the result is a white opaque material in the first case and a transparent material in the second case. The resulting films were washed free of excess monomer and then soaked in the buffer to be used in the fibrinogen adsorption experiment for 10 days at 37 °C prior to the actual experiment. 

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). 

Figure 6. Fibrinogen adsorption isotherms on Silastic, poly(NVP)/Silastic, and poly(H EM A)/Silastic. Untreated Silastic and Silastic grafted with poly-(NVP) (2.7 mg/cm ) or poly(HEMA) (5.8 mg/cm ) were equilibrated at 37°C for 20 hrs in fibrinogen solution of the depicted concentration in O.OJM HEPES, 0.147M NaCl, 0.02% azide, pH 7.4 and then rinsed by dilution displacement and extensive soaking with buffer at room temperature.

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... 

Figure 7. Plasma fibrinogen adsorption onto poly( HEM A)/Silastic. Poly-(HEMA)-grafted Silastic (ca. 5 mg/cm ) films were equilibrated in a plasma solution (containing H-fibrinogen) at 37°C for the time depicted and then rinsed briefly by the dilution displacement technique with 0.01 M HEPES, 0.147M NaCl, pH 7.4, and then counted.

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. 

Figure 8. Fibrinogen adsorption onto PS/Poly(PEGMA) segregated brushes. The PS and PolyPEGMA brushes thickness are 7.5 nm and 21 nm, respectively. SPM topography image 2x2 microns.

Fibrinogen adsorption onto the most highly grafted poly(HEMA)/Silastic films (5.8 mg/cm ) was the same as onto films having only about one-fifth the graft, but films with grafts much below this point (1 mg/cm ) showed increased adsorption characteristic of the underlying Silastic. 

The saturation level of fibrinogen adsorption from buffer varied by about a factor of four in the order poly(HEMA)/Silastic < Silastic = poly(NVP)/Silastic. The NVP graft was intermingled with Silastic so adsorption to pure NVP was not obtained. 

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. 

CP composites of both poly(vinyl alcohol) (PVA) [83-88] and poly(ethylene glycol) (PEG) [87,89,90] have been fabricated by both chemical and electrochemical polymerization of either monomer solution loaded or dispersed into hydrogel networks. Li et al. reported that tetraethylammonium perchlorate (TEAP) doped PPy-PVA composite was more hydrophilic than PPy/TEAP film and showed less fibrinogen adsorption on the surface than the CP control film. The PPY-PVA composite maintained intrinsic conductivity of PPy/TEAP film (7 S cm ) and the porous structure of the composite promoted neural cell attachment and spreading in the model clonal line, PC 12 [86]. 

Due to the important role of adhesion of plasma proteins in determining blood compatibility and the key role of fibrinogen in these processes, investigators developed an in vitro assay to test fibrinogen adsorption to polymer surfaces. Casting of 46 different polymers (44 polyarylates, poly(lactic... 

Based on the relationship between protein adsorption and thromboge-nicity, a method was reported for fibrinogen adsorption/desorption measurements as a prescreening method. Processes for the coating of polymers with poly-acrybnitrile and with carbon were discussed, and results on layers on flat films, the inside of tubes and vascular prostheses, and on membranes were described. 

The hydrophilization of poly(ether sulfone) surfaces used for the production of ultrafiltration membranes for hemodialysis is of special interest Poly(ether sulfone) is a chemically inert and highly thermostable polymer showing a hydrophobic surface which leads to high fibrinogen adsorption and subsequent thromboembolization [111]. This effect is generally avoided by non-desirable heparin doses. The hydrophilization of poly(ether sulfone) surfaces by plasma-induced graftcopolymerization and the introduction of a hydrogel layer without... 

In summary, with regard to the development of a blood-compatible polymer surface based on poly(ether sulfone), an athrombotic surface is achieved by hydrogel coating using plasma-induced graftpolymerization of HEMA. Nevertheless, this evaluation is based on only three in vitro parameters, i.e. blood compatibility, fibrinogen adsorption, and platelet adhesion, and hence is by no means comprehensive. 

Huang, N.P., Michel, R., Voros, J., Textor, M., Hofer, R., Rossi, A., Elbert, D.L., Hubbell, J.A., Spencer, N.D. Poly(L-lysine)-g-poly(ethylene glycol) layers on metal oxide surfaces surface-analytical characterization and resistance to serum and fibrinogen adsorption. Langmuir 17,489-498 (2001). doi 10.1021/la000736+... 

Poly(L-lysine)- -poly(ethyIene glycol) Layers on Metal Oxide Surfaces Surface-Analytical Characterization and Resistance to Serum and Fibrinogen Adsorption... 

Kuo WH, Wang MJ, Chien HW, Wei TC, Lee C, Tsai WB. Surface modification with poly(sulfobetaine methacrylateco-acrylic acid) to reduce fibrinogen adsorption, platelet adhesion, and plasma coagulation. Biomacromolecules 2011 12 4348-56. 

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