Abstract: The present invention provides a platelet-rich plasma with high activities in an easy and economical manner. The platelet-rich plasma is obtained by aggregating and precipitating erythrocytes from collected whole blood selectively and facilitatively without employing centrifugation. For example, the plasma is obtained by the addition of a polymer having a residue of an organic phosphate compound. Specifically, the polymer having a residue of an organic phosphate compound can be added to whole blood and allowed to stand for a specific time, thereby to selectively and facilitatively aggregate and precipitate erythrocytes to give a supernatant. The supernatant contains much platelets which exist in their extremely intact state similar as in a living body and simultaneously provides a platelet-rich plasma with high activity comprising much plasma proteins such as fibrinogen and leukocytes.

Abstract: An object of this invention is to provide platelet-rich plasma having high activity easily and at low cost. The object is achieved by a method for preparing platelet-rich plasma comprising a step of adding a water-soluble polymer compound to whole blood obtained by blood collection. For example, by adding poly-L-glutamic acid to whole blood and allowing the mixture to stand still for a definite period, it is possible to obtain platelet-rich plasma having high activity that contains blood plasma components containing much fibrinogen in addition to platelets in the supernatant and blood cell components including white blood cells. This invention also includes the platelet-rich plasma and the use thereof as well as a kit for preparing platelet-rich plasma.