Platelet adhesion to commercial and modified polymer materials in animals under psychological stress and in a no-stress condition.

It is well known that stressful stimuli change blood functions and that protein and platelet parameters are altered in humans and animals subjected to stress. We have examined the influence of psychological stress on the morphological responses of platelets on commercially available materials [polyester (VP), fluoropassivated polyester (VPF), non-woven benzylic ester of hyaluronic acid (Hyaff11)] and on materials synthesised (PUPA) and/or surface modified by sulphation (Hyaff11S) or by immobilisation of the anticoagulant molecules heparin and sulphated hyaluronic acid (PUPA-Heparin, PUPA-HyalS, HyalS-PET). Moreover, the anticoagulant activity (i.e. thrombin inactivation) of the materials was analysed. In the no-stress condition, the surfaces with a low degree of platelet adhesion were Hyaff11S, HyalS-PET, PUPA-Heparin and PUPA-HyalS. Hyaff11, PET and PUPA had the highest number of adherent platelets within the series. VP and VPF exhibited an intermediate behaviour. The exposure of animals to stress induced a dramatic change in platelet number and morphology on PET, HyalS-PET, PUPA, PUPA-HyalS and Hyaff11: there was a higher degree of platelet adhesion, increased platelet spreading and the appearance of pseudopodia. In VP, VPF, Hyaff11S and PUPA-Heparin, there were no changes in platelet adhesion in stress conditions with respect to the no-stress condition; the latter two materials, the only ones able to prolong thrombin time, had a very low number of adherent platelets.