Comparison of Platelet Adhesion on Different Hard Material Coatings and Bonding Agents for Ventricular Assist Devices in a Flow Chamber

In end-stage heart failure patients, rotary blood pumps (RBPs) are implanted as ventricular assist devices (VADs) to supply the body with sufficient blood flow. These pumps expose blood to foreign surfaces, leading to potential adverse events like formation of thrombi. Such devices require high wear resistance, especially in scratch-prone areas, to minimize this risk and ensure long-term functionality. However, commonly used titanium-alloys offer only poor wear resistance. Therefore, more durable coatings are developed and implemented. This study explores platelet adhesion as indicator for the risk of thrombus formation on various surface coatings using an in-vitro flow chamber model. The surfaces included the hard material coatings (HMCs) Silicon Diamond-Like Carbon (SiDLC), Titanium Nitride with droplets (lumps on the surface) (TiN_D) and Titanium Nitride without droplets (TiN), the bonding agents Chrome (Cr) and Chrome Nitride (CrN), uncoated Ti6Al4V (Ti) as reference and Aluminum (Alu) as positive control. The surface area covered by platelets was quantified using fluorescence microscopy and normalized to the platelet count of the respective blood sample, resulting in a normalized percentage of covered surface area NCSA in [%/plateletcount<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">exp</inf>]x10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>/μL. Alu exhibited the highest value (NCSA=0.087), with significant differences compared to CrN (NCSA=0.003) and SiDLC (NCSA=0.003) (p<0.05), a medium Wilcoxon effect size compared to all HMCs and Ti, and a weak effect compared to Cr. Cr showed the second-highest platelet deposition (NCSA=0.036), with significant differences (p<0.05) compared to CrN, a medium effect compared to CrN, Ti (NCSA=0.002), TiN (NCSA=0.002), and SiDLC, and a weak effect compared to TiN_D (NCSA=0.004) and Alu. CrN and the HMCs showed lower platelet coverage with a medium effect compared to Alu. CrN, TiN_D and SiDLC showed no effect compared to Ti, suggesting good hemocompatibility. Overall, CrN emerged as suitable bonding agent and HMCs like SiDLC and TiN_D demonstrated to be promising for use in blood-contact applications.