Surface interactions with blood

In this connection, it is to be noted that polyamine-modified po y(HEMA) surfaces exhibit surprisingly reduced interaction with blood proteins and cells (e.g. erythrocyte, platelet, lymphocyte etc.), as will be discussed in Sects. 4.3 and 4.4. The present author considers that there are probably closely related mechanisms between the suppressing effect of the poly(DIPAM) or (Methacrol)-modi-fied SPU and that of the polyamine-modified poly(HEMA) surfaces, with regard to their mode of interaction with the biological elements. 

Tan, J. S., D. E. Butter eld, C. L. Voycheck, K. D. Caidwell, and J. T. Li. 1993. Surface modi cation of nanoparticles by PEO/PPO block copolymers to minimize interactions with blood components and prolong blood circulation in rat iomaterials14 823-833. 

The change in biological response of the adsorbed fibrinogen molecule (conversion), is also noticeable with platelet adhesion studies. In confirmation of earlier studies of Zucker and Vroman (5), we found that, usually, less platelets adhered to areas of glass slides exposed to platelet-poor plasma for 3 min than areas exposed for 3 s. When, however, a gel-filtered platelet suspension was used in place of platelet-rich plasma, a dramatic difference in the number of platelets attached to the surface previously exposed to platelet-poor plasma for 3 s or 3 min occurred. Therefore, this more reproducible protocol was used to study not only the adhesion of platelets onto artificial surfaces but also as a probe of conversion. For this purpose we chose a series of block copolymers with controllable domain morphology (phase separation on a molecular scale) and different surface energies (wettability). Previous studies have shown that the degree of phase separation influences the interactions with blood components (6,7). 

In summary, the surface chemical and morphological structures of block copolyether-urethane-ureas may be determined by ESCA and FTIR coupled with internal reflectance techniques to probe the surface and bulk structures. These ESCA and FTIR data are being used to model the domain-interface structure of these copolyurethanes and their interaction with blood protein. 

A.S. Hoffman. Modification of material surfaces to affect how they interact with blood. Ann. NY. Acad. Sci. 516 96-101 (1987). 

Another hydrophilic polymer that has received considerable attention is poly(ethylene oxide) [17, 18]. While poly(ethylene oxide) surfaces have been shown (like hydrogels) to have relatively low interactions with blood proteins and cells in in vitro studies and in some animal models, the suitability of such polymers for actual device applications and long-term implants has not been established. 

After QDs enter the venous circulation, they may adhere to or interact with blood components or cells, so the distribution of QDs in vivo depends mainly on their size and surface properties. NIR QDs ( 5 nm) will gradually be eliminated from the body the larger the hydrodynamic diameter, the longer the retention time. " Some QDs, especially those with larger hydrodynamic diameters, will undergo endocytosis by macrophages in the reticuloendothelial system, thereby prolonging their stay in the body. 

Our basic assumption is that a polymer surface which does not interact with blood at all, does not induce thrombus formation. In other words, the polymer surface, which does not adsorb any plasma protein, must be blood-compatible. 

There still remain many problms to be solved for developing an excellently blood-compatible polymer. At least, a direct comparison of the blood compatibility in vivo by means of a powerful evaluation method is required for each of the polymers which different research groups have synthesized according to their own hypothesis. Our diffuse surface hypothesis is only one of these hypotheses. The materials illustrated in Fig. 29 may contain a large fraction of water on their surface, leading to minimum interactions with blood. 

Further biocompatibility issues of PVA were addressed by Fujimoto et al. [114]. This work focused on PVA gels that had been annealed in the presence of glycerol. When such materials were examined for their interactions with blood components, reduced adsorption and platelet adhesion were observed due to the addition of glycerol. Glycerol essentially altered the surface of the PVA gel. They described the mechanism as being due to increased tethered PVA chains on the surface which served to decrease the direct contact of blood components with the surface. 

Ikada, Y., Suzuki, M., Tamada, Y. Polymer surfaces possessing minimal interaction with blood components. In Polymers as biomaterials, pp 135-147. Springer, Heidelberg (1984)... 

Polyphosphazenes may provide particular advantages over their organic counterparts in the field of biomedical applications. For artificial organ research, materials can be synthesized that have specific surface properties, extreme stability under hydrolytic or oxidative conditions, and minimal interactions with blood or living tissues. Polymers that possess fluoroalkoxy or aryloxy side groups... 

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