Countess™ 3 Standard Slide

The Countess 3 Standard Slide is a ready-to-use and reusable slide used as a reference for cell counting, viability, and fluorescence on the Countess automated cell counters. This slide is optimized for ensuring accurate performance in brightfield cell counting applications when using Countess II, Countess II FL, Countess 3, and Countess 3 FL automated cell counters. The permanently mounted microspheres on the Countess 3 Standard Slide enable repeatable counts to be easily achieved over the life of the slide, with variability only encountered upon changing instrument gating settings.

The Countess 3 Standard Slide is supplied ready-to-use and does not require any special handling or sample preparation, thus eliminating the major source of count-to-count variability. This makes it an ideal reference slide that can be used to achieve consistent and repeatable cell counts and viability measurements across days or between Countess 3 instruments. The slide can also be used for demonstrating how to use the Countess automated cell counters for both brightfield and fluorescence cell counting.

Features of the Countess 3 Standard Slide include:

• Accurate—ready-to-use slide helps eliminate the error involved in creating standard solutions and dilution series
• Flexible—optimized for use in Countess II, Countess II FL, Countess 3, and Countess 3 FL automated cell counters
• Fast—supplied as a pre-loaded, immobilized, bead suspension; no preparation or mixing required
• Convenient—one standard slide for both brightfield and fluorescence cell counting applications

Immobilized microspheres mimic cell counting samples

The Countess 3 Standard Slide contains 15 μm microspheres that are permanently mounted in a cell counting chamber at a concentration of 0.5–1.5 x 10⁶/mL. This unique, inert, immobilized bead mixture mimics the appearance of a 1:1 mixture of live and dead cells stained with trypan blue under brightfield illumination, which is the most common cell counting analysis method. The permanently mounted microspheres provide a stable sample that can be used repeatedly for verification of instrument performance. Please note that while the exact bead concentration for an individual slide is not specified, the bead concentration for each slide will fall in the 0.5–1.5 x 10⁶/mL range and remain consistent over time.

Fluorescent microspheres enable fluorescence cell counting

The Countess 3 Standard Slide offers further utility by containing two populations of fluorescent beads that cover the fluorescence spectrum from blue to far red, thereby allowing analysis with a variety of EVOS light cube combinations available to Countess II FL and Countess 3 FL counter users. When viewed on the Countess 3 FL counter, the 15 μm microspheres are also fluorescent in a 1:1 mixture, providing approximately 50% detection with a DAPI or GFP light cube and approximately 50% detection with an RFP, Texas Red, or Cy5 light cube. The fluorescent microspheres enable users to perform or demonstrate fluorescence-based cell counting with the Countess 3 Standard Slide.

Stable standard for routine performance verification

The Countess 3 Standard Slide provides a stable sample containing microspheres that are visible in both brightfield and fluorescence channels and mimic a mixed population of live and dead cells. This allows users to easily perform routine verification of instrument performance for automated cell counting and demonstrate instrument usage. The immobilized microspheres eliminate sample variability, enabling reliable ongoing quality control.