Abstract: An apparatus for preloading magnetic particles or cells onto a medical device includes a device carrier and a particle carrier attached over the device carrier. At least one magnet is inserted into the device carrier, the at least one magnet extending inside a section of the device carrier, over which the particle carrier is attached, to attract magnetic particles or cells to the particle carrier when the apparatus is placed in a suspension of magnetic particles or cells. A method for preloading magnetic particles or cells onto a medical device includes attaching one or more magnets to a device carrier, attaching a particle carrier to the device carrier in proximity to the one or more magnets, and inserting the device carrier with the attached particle carrier and the one or more magnets into a suspension containing magnetic particles or cells to preload the particle carrier with magnetic particles or cells.