Development of a method for measuring blood coagulation using   superparamagnetic iron oxide nanoparticles and an alternating magnetic field
  We developed a method for measuring blood coagulation using superparamagnetic iron oxide nanoparticles (SPIONs) and an alternating magnetic field (AMF). The 3rd and 5th harmonic signals from SPIONs mixed with blood induced by AMF were detected using a gradiometer coil. Blood coagulation was induced artificially by adding CaCl2 solution to whole blood of sheep at various temperatures and hematocrits. We calculated the coagulation rate (k) and normalized signal intensity at infinite time (Sinf) by fitting the time course of the normalized 3rd harmonic signal to S(t)=(1-Sinf)exp(-kt)+Sinf. The k values increased significantly with increasing temperature and decreased significantly with increasing hematocrit. The Sinf values decreased significantly with increasing temperature and tended to increase with increasing hematocrit. Blood anticoagulation was induced by adding heparin to the whole blood sampled from mice. There were significant differences in both the 3rd and 5th harmonic signals between groups with and without heparin at 25 min or more after adding heparin. We also calculated the 3rd and 5th harmonic signals for viscosities ranging from 0.001 to 1 kg/m/s, with an assumption that the magnetization and particle size distribution of SPIONs obey the Langevin theory of paramagnetism and log-normal distribution, respectively. The 3rd and 5th harmonic signals increased slowly with increasing viscosity and had peaks at approximately 0.015 and 0.025 kg/m/s, respectively. After these peaks, they decreased monotonically with increasing viscosity. These results confirm the rationale of our method. In conclusion, our method will be useful for measuring blood coagulation and anticoagulation and for studying their processes. 
Kenya Murase
physics.med-ph