The TopCount Microplate Scintillation and Luminescence Counter can be used to count samples prepared in MultiScreen microplates. These plates are designed so that all assay steps are performed in a single microplate. However, conventional approaches still require the transfer of filter disks into discrete liquid scintillation (LS) vials or gamma tubes for quantitation. TopCount offers the ability to count labeled samples in MultiScreen filtration plates directly, thereby minimizing handling and consumables costs and increasing sample throughput. This paper describes several studies comparing direct counting in TopCount to conventional methods.
The MultiScreen Assay System (Millipore Corporation) is a microplate filtration system suited for screening procedures that require separation of bound from free radiolabel. Assays which have been performed in the MultiScreen system include cell-based receptor binding and cell proliferation studies. A variety of other applications can be performed with MultiScreen. A number of publications from Millipore Corporation, entitled "MultiScreen Methods", describe various applications in detail.
The MultiScreen system consists of filter-bottom microplates made with one of several types of membrane filters. The membrane-bottom wells can hold aqueous buffers and assay media within the plate until separation is carried out on a vacuum filtration manifold. After removing the underdrain, the 96 individual filters are typically punched into LS vials or gamma tubes using a punch device supplied by Millipore. The MultiScreen system permits significant increases in sample preparation speed, since pipetting and incubation can be done with automated microplate equipment. However, overall throughput is hampered by the need to punch samples into discrete counting vials. Large numbers of vials, significant amounts of LS