Detecting and understanding the dynamics of blood coagulation on a material’s surface: An optical reflectance approach

Despite the technological advancement in blood-contacting biomedical devices, issues related to thrombosis remain a persistent challenge. These devices not only include implants such as artificial heart valves and stents but also surgical tools and instruments. This makes hemocompatibility an important parameter to be considered before developing any material for a blood-contacting device. The two oldest methods, including the mechanical tilting method and the free-hemoglobin method, lack temporal accuracy and quantitative analysis. Our work gives an accurate and quantitative analysis to measure the blood clotting time of various materials that can be used as implant devices. The system relies on measuring the change of reflectance as blood clots on a surface and measures the clotting time and rate by analyzing the time dependent reflectance curve. The system consists of an automated injection system, a heater and temperature controller, a red laser and polarizer assembly, and a highly sensitive photodetector. As the blood clotting process begins, the sample surface becomes turbid, causing a change in voltage in the detector. The time taken for this "voltage change" corresponds to clotting time. Our system shows a prothrombin time of 12.6 s and an activated partial thromboplastin time of 31.16 s on the PTFE surface, close to the control due to its hydrophobicity. The electronics and device configuration used in our system give a temporal resolution of 5.7 ± 0.6 ms in the clotting time determination. Our design is compact, precise, accurate, and devoid of manual observation and errors.