Glass platelet adhesion

Fig 1. Platelet adhesion end spreading to protein coated glass, for IS minutes exposure to wadied platdetst... 

The photomicrographs of platelet adhesion on protein coated glass, after e qx)sing with wasted cells and whole blood, under lOOOS shear, for 15 minutes are shown in figures 2 and 3 respectively. 

Fig 2. PhotMnicrograph of the platelet adhesion to Glass (A) and Fg coated glass (B) for 15 minutes from washed cells under lOOOS shear. 

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

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). 

The platelets, at four random fields, were counted visually on a Zeiss Ultraphot II microscope using reflected light and Nomarski optics at a magnification of 1280 X and a field of view of 7542 pan2. At least four samples of each polymer were tested for each experiment, and each experiment was repeated at least once with a different donor. For the glasses, at least 1-2 samples were tested per experiment. Conversion was expressed as the percentage difference between platelet adhesion at 3 s and 3 min of platelet-poor plasma exposure with respect to the 3-s platelet-poor plasma exposure. 

Statistical Analysis. All data for a particular donor were normalized with respect to the hydrophobic glass at 3 min of platelet-poor plasma exposure for that donor, that is, platelet adhesion at 3 min of platelet-poor plasma exposure to hydro-phobic glass was 100%. A one-way analysis of variance was performed, using each material and time of platelet-poor plasma exposure as a variable. For each material and time, the normalized platelet counts for all the donors were summed, and Scheffe s multiple comparisons were performed. For the difference between the two SBS morphologies, a student s t test was used. Data are presented as the mean of the normalized average from each donor and the pooled standard deviation. 

The polyurethane in the phase-separated state (ANN), however, behaved in a manner similar to certain other hydrophobic surfaces (3), including siliconized glass, in that platelet adhesion was independent of the time of exposure to plasma, that is, no difference between 3 s and 3 min existed. The hydrophobic SBS block copolymer, on the other hand, attached significantly (P < 0.025) less platelets at 3 min of plasma exposure. The effect was relatively more predominant in the mixed state as the percent decrease in platelets attached at 3 min (conversion) was 56 compared with 34 for the phase-separated state (Table II). The conversion, however, was far less than the 99% observed on the hydrophilic glass. 

Fibrinogen 3-5 polystyrene silicone rubber glass platelets fibroblasts red cells adhesion and release enhanced (11) adhesion enhanced (12) adhesion prevented (13)... 

Platelet adhesion did not correlate with fibrinogen adsorption to glass pretreated with a series of plasma dilutions since the experiments show the greatest number of adhering platelets did not occur where maximal fibrinogen adsorption occured. 

Additional experiments were performed to compare fibrinogen- and albumin-coated glass with respect to the details of the platelet adhesion process (30). Using purified forms of fibrinogen and albumin it was demonstrated with 5iCr-labelled platelets that the net rates of adhesion of platelets to these proteins are equal. The next task was to determine if the pathways leading to this were the same. With video-microscopy of mepacrine labelled platelets, we found a difference in pathways, see Table II. At a wall shear rate of 80s-i, the percent of platelets which adhere... 

Platelet adhesion to subendothelium at high wall shear rate has been shown to be mediated by vWF ( ), Preliminary results in the capillary perfusion system, using glass capillaries uncoated or coated with purified humian albumin or bovine collagen, showed an increase in platelet deposition in the presence of vWF on the albumin surface at low... 

PEG-phenylazide and photoinduced grafting onto DDS-glass is shown in Figure 4. Platelet adhesion and activation was prevent on PEG-gr ted DDS-glass. 

Figure 30 Antifouling surfaces platelet adhesion on (a) OTS-coated glass coverslip and (b) dendritic snrfactant polymCT-coated OTS-glass coverslip. (Reprinted with permission from J. Zhu and R. E. Marchant, Biomacromolecnles, 2006, 7, 1036. (2006) American Chemical Society.)...

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