CUSTOMIZED NEONATAL INCUBATOR FOR MEASUREMENT OF PLATELET-ARTIFICIAL MICROVASCULAR GRAFT INTERACTIONS UNDER CONTROLLED FLOW, TEMPERATURE, AND TRANSMURAL PRESSURE

A neonatal incubator has been custom modified to enable measurement of initial platelet retention on biomaterials in vitro under clinically relevant hemodynamic conditions. To calibrate this device, platelet retention on several materials having microconduit geometry (0.7-1.0 mm i.d.) has been measured after perfusion with citrated whole blood (containing 111Indium-labelled platelets) at a shear rate of 312 s-1, 37-degrees-C, and 80 cm H2O transmural pressure. The relative reactivity of these materials toward platelets was: glass < Fibrinogen(Fg)-coatedglass < Fg-coated polyethylene < polyethylene approximately = Expanded polytetrafluoroethylene. Interindividual variation is relatively large (coefficient of variation = 35.5 +/- 9.3%), but comparison to intraindividual controls reduces the variability to 14.8 +/- 10.3%, a level which is suitable for economical testing of platelet retention to bio-materials in the presence or absence of drugs. This approach may have particular value in the study of the mechanism of platelet interactions with artificial microvascular grafts under perfusion conditions which are relevant to the first moments of flow, when initial platelet deposition occurs.