Interactions of blood with

The qualitative thermodynamic explanation of the shielding effect produced by the bound neutral water-soluble polymers was summarized by Andrade et al. [2] who studied the interaction of blood with polyethylene oxide (PEO) attached to the surfaces of solids. According to their concept, one possible component of the passivity may be the low interfacial free energy (ysl) of water-soluble polymers and their gels. As estimated by Matsunaga and Ikada [3], it is 3.7 and 3.1 mJ/m2 for cellulose and polyvinylalcohol whereas 52.6 and 41.9 mJ/m2 for polyethylene and Nylon 11, respectively. Ikada et al. [4] also found that adsorption of serum albumin increases dramatically with the increase of interfacial free energy of the polymer contacting the protein solution. 

To clarify the mechanism of enhanced thromboresistance of such polymers, the state of the blood clotting system before and after the contact with the polymer was examined I36) (Table 19). Obviously, the changes of the blood clotting system parameters are of the same type as those accompanying the interaction of blood with HCP (see Table 16) but essentially exceeding the latter. Consequently, the heparin-protease-... 

Fig. 12. Interaction of blood with surface having grafted water-soluble chains...

The interaction of blood with PVC-P based on a phthalate and trimellitate plasticiser has shown that there is a higher reactivity for the trimellitate, which correlated with the plasticiser distribution at the polymer surface (316). Another important aspect is for the medical packaging to be suitable for sterilisation of the contents. Details are available of improving the gamma irradiation stability of PVC-P in order to retain colour (447). In addition to unacceptable colour formation, excessive shifts in pH and extractables can occur in inappropriately stabilised PVC-P (301). An additive system, based on materials approved for medical use, has been developed to give low extractables and low blush with good colour and processability (239). The effects of different plasticisers... 

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... 

Baier, R. E., Dutton, R. C., Initial Events in Interactions of Blood with a... 

Methodologies to evaluate the interaction of biomaterials with blood and blood components vary from in vitro systems, where anticoagulated blood or blood fractions are contacted with surfaces in a variety of configurations, to in vivo procedures, where tubes, sheets, etc. are inserted into the vascular system. A compendium of these techniques that seek to understand the complex interactions of blood with surfaces recently was assembled (1). 

The Canine Model. While ex vivo models often are considered to be an improvement over in vitro biocompatibility test systems, the problem of describing extremely complex blood—polymer interactions still remains. In this study, we used radioisotope-labeled proteins and platelets and scanning electron microscopy. In other studies, we applied immunolabeling techniques and transmission electron microscopy. The application of these tools to an in vivo or ex vivo system provides more pertinent data than that often obtained in an in vitro system. Through this approach we hope to gain some insights into the complicated interactions of blood with biomaterials. 

Mosher, D.F. In Interaction of Blood with Natural and Artificial Surfaces Salzman, E., Ed. Dekker New York, 1981 p. 85. 

FTIR spectroscopy has proven to be particularly useful in gaining an understanding of the biocompatibility phenomenon. It is believed [746, 841, 856, 857] that protein adsorption is the initial step in the interaction of blood with implanted biomaterials, followed by adhesion of cells and subsequent tissue attachment. This implies that the substrate surface characteristics influence the process, which was confirmed by ATR studies of albumin adsorption on calcium phosphate bioceramics and titanium [763] and segmented polyurethane [764], albumin and fibrinogen on acetylated and unmodified cellulose [765, 766], poly(acrylic acid)-mucin bioadhesion [767], polyurethane-blood contact surfaces [768], and other proteins on poly(ester)urethane [769], polystyrene [767, 771] and poly(octadecyl methacrylate) [771] and by IRRAS study of adsorption of proteins on Cu [858]. Another branch of IR spectroscopic studies of protein adsorption relates to microbial adhesion (Section 7.8.3). 

This book is highly recommended. This state-of-the-art text covers in detail essentially all important hematological aspects of cardiovascular device blood compatibility. In particular, Chapter 76, Interaction of blood with artificial surfaces, which considers many theoretical, experimental, and animal studies, and Chapter 77, Artificial devices in clinical practice, which describes clinical device thromboembolic complications, are of great practical value. 

Numerous controversial theories on blood-compatible polymers have been reported, because the interactions of blood with polymer surfaces leading to thrombus formation are governed by many chemical, physical, and biological parameters and difficult to analyse in detail. The important variables affecting thrombus formation on biomaterials include chemical composition of the surface, physical texture of the surface, disturbance of blood flow induced by the polymer, the kind of animals used, the physical conditions and local place of the tested body, etc. Furthermore, the evaluation methods employed for blood compatibility are important because different evaluation methods lead to different conclusions therefore, a standard sample is strongly desired At least, in the final test stage it is essoitial to evaluate the blood compatibility under conditions applied in practice. 

E.W.Salzman, In vitro assessment of interaction of blood with model surfaces, J.Lab.Clin.Med. 92 9G4 (1978)... 

Polytetrafluoroethylene, polyurethanes, polyethylene, silicones and acrylates have been proposed for replacement of both hard and soft tissues. These biomaterials must satisfy two in5)ortant criteria to provide an useful function in a biological environment they should possess the proper physical characteristics as replacement materials and should exhibit compatible interfacial properties with surroimding tissues and fluids. The interaction of blood with foreign surfaces resulting in thrombogenesis has received considerable attention, but still represents a problem. 

Interactions of Blood with Multiphase Polymers Effect of Sulfonate-Ester-Contalnlng Domains on Platelet Reactivity... 

As shown above, detailed knowledge of the interactions of blood with foreign surfaces and the significance of these reactions to overall blood compatibility is, as yet, incomplete. As a result, research directed toward improved materials has been hindered. 

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