Visualization of platelet deposition in a flow chamber

Abstract The formation of thrombi is still a challenge when it comes to ventricular assist devices (VADs). This can be caused by the subsequent deposition of proteins and platelets on foreign surfaces. In VADs, the blood contacting components are mainly made of titanium alloys due to hemocompatible properties and corrosion resistance. However, surfaces where mechanical contact of the rotor and the stator occur like bearing areas of axial VADs require high wear resistance due to the greater potential of scratches. Therefore, an in vitro test bench to optically investigate the deposition of fluorescent labelled platelets on the protein layer of different surfaces is hereby presented, aiming to investigate the potential for thrombi formation of five different inorganic hard material coatings on titanium. The coating materials included Titanium Nitride (TiN), Titanium Niobium Nitride (TiNbN), Diamond-Like Carbon (Ionbond-Medthin-43 (DLCI) and Oerlikon Balimed A (DLCO)) and Wolfram Carbid Oerlikon Balimed C (WC). Uncoated titanium (Ti) was investigated as reference. Heparinized human whole blood was incubated with Mepacrine (fluorescent dye) and then pumped through a flow chamber with defined shear rate conditions over the samples. The adhered platelets were visualized via inverted fluorescence microscopy. The analyzation of the green values and the binary image of the generated fluorescent picture offers conclusions about the platelet accumulation and the percentage of the covered surface area, respectively. Statistical analysis showed a significant lower potential for platelet deposition for TiN compared to Ti and no significant differences for the rest. It can be concluded that none of these coatings have a higher potential for platelet deposition than Ti and therefore point towards suitability for blood contacting components.