Nanosized blood microparticles

Microparticles (MPs) have important physiological and pathological roles in blood coagulation, inflammation and tumor progression. In recent years MPs also have been recognized to participate in important biological processes, such as in signaling and in the horizontal transfer of their specific proteins and mRNAs. However, studies of MPs have been hampered by the lack of methods for the sensitive detection and accurate quantification of MPs. Thus, we have developed a new methodology by using atomic force microscopy (AFM) and cryo-electron microscopy (cryo-EM) to detect, quantify and characterize MPs in plasma. We have shown that AFM detects 1000-fold more platelet derived-MPs than a conventional flow cytometry does. These MPs have diameters ranging from 10-475 nm with a peak at 67.5 nm, which is clearly far below the detection limit of flow cytometry. By using cryo-EM we found that the number of lipoprotein particles exceeds that of MPs or exosomes in plasma. We also demonstrated that by using immuno-magnetic beads selected subset of MPs could directly be captured/depleted from plasma and assessed for MP-associated tissue factor activity. In the future the measurement of MPs will perhaps serve as a diagnostic tool to identify and predict diseases, like cancer.