During blood coagulation, ADP is secreted by activated platelet cells, leading to platelet aggregation. This ADP-induced platelet activation is counteracted by nucleoside triphosphate diphosphohydrolase (NTPDase). NTPDase rapidly metabolizes ADP to AMP and inorganic phosphate. In this study, polyethylene terephthalate (PET) surfaces were modified by immobilizing NTPDase to inhibit ADP-induced platelet adhesion.

To understand the kinetics of immobilized NTPDase, NTPDase was covalently attached to PET, using ethylenediamine cross-links. Kinetic studies were performed by exposing an ADP solution to the NTPDase-modified PET in the presence of 5 mM CaCl₂ and 0.1 M Tris buffer (pH 7.4). The rate of hydrolysis of ADP for both immobilized and free NTPDase at physiological conditions (37°C and pH 7.4) was studied by measuring the release of inorganic phosphate. Both immobilized and free NTPDase kinetics were modeled and compared.

The activity of immobilized NTPDase was much higher (~25 mM of inorganic phosphate released in an hour per cm²) compared to a previous study (~1.4 mM of inorganic phosphate released in an hour per cm² [1]). This improved activity of immobilized NTPDase increases the potential haemocompatibility of NTPDase-modified polymers. Future studies will evaluate in-vitro studies of NTPDase modified polymers using platelet suspension, platelet rich plasma and whole blood to establish the effectiveness of the polymers in inhibiting platelet adhesion.

Reference:

1. Marconi, W., Mi, S.D., Bartoli, R. and Pittalis, F., Preparation of biocompatible materials by immobilization of apyrase. 1983. E. N. I. Ente Nazionale Idrocarburi, Rome, Italy: United States of America.