Compositions and methods for maintaining platelet functionality and extending the shelf-life of platelets are described. Platelet preservation compositions include a photosensitizer and a plurality of platelet preservation agents. A method for preserving platelets and extending their shelf-life includes irradiating a platelet mixture containing a photosensitizer under conditions sufficient to activate the photosensitizer and inactivate microbes in the platelet mixture to form a microbe-depleted platelet preparation. A plurality of platelet preservation agents are added to the microbe-depleted platelet preparation for extending the platelet shelf-life. Prior to transfusion, the photosensitizer and platelet preservation agents can be removed by diafiltration and/or the use of compound adsorption devices.
