Using the Nanodrop™ to Reduce the Cost of Reagents in a Typical Luminescence Assay
Introduction
Traditional luminescence assays can be performed in 384-well microplates, at volumes of 50 µL, using a commercially available liquid handling device such as a Beckman-Coulter Biomek FX (Fullerton, CA). Reduction of assay volumes is desirable for the obvious cost savings, but additional data-quality benefits can be realized through gains in signal to noise ratios and improvements in assay Z factors. Reduction of total assay volumes to 10 µL or less is problematic for traditional contact dispensing devices due to positional inaccuracies and difficulty with touch-offs required for effective dispensing. Non-contact, solenoid-based dispensing offers high precision at volumes less than 50 µL. In collaboration with Chiron Corporation (Emeryville, CA), we designed a simple side-by-side experiment to show that Innovadyne’s Nanodrop™ liquid handler was able to not only reduce total-assay volumes, but also improve results in comparison to data obtained through classical liquid handling.
Methods and Materials
Using DMSO as a pooled sample, assay viability can be assessed with a simple luminescence assay. The liquid handling protocol can be seen in the table below (see figure 1). For the 50 µL assay, the pooled 1.25 µL DMSO sample was dispensed using a PerkinElmer PlateTrak system (Downers Grove, IL). The two 25 µL reagent additions were performed on a Beckman Biomek FX. The first dispensed the 1.25 µL of DMSO into the plate followed by two, 25 µL reagent dispenses. Controls were place in the first and last two columns and plates were read on a PerkinElmer Trilux reader. For the 10 µL assay, all dispenses were performed using the Nanodrop 8-channel dispenser. MatriCal 384-well, low-volume plates (Spokane, WA) were used and read on the PerkinElmer Trilux reader.
Luminescent Assay Conditions
| 50 µL Assay | 10 µL Assay | |
| Dispensing technology | Traditional | Nanodrop |
| 384-well black plate type | Greiner | MatriCal |
| Volume DMSO | 1.25 µL | 0.250 µL |
| Volume Solution P to columns 1 - 24 | 25 µL | 5 µL |
| Volume Solution A to columns 3 - 22 | 25 µL | 5 µL |
| Volume Solution D to columns 1, 2, 23, 24 | 25 µL | 5 µL |
| Detection device | PerkinElmer Trilux | |
Figure 1. Dispense protocol for 50 µL and 10 µL assays
* (Data courtesy of Dr. Timothy D. Dawes of the Chiron Corporation)
Results and Discussion
The data* shows that use of the Nanodrop device resulted in improvements in precision (see figure 2), assay Z factor (see figure 3) and signal to noise (see figure 4) in comparison to traditional liquid handling at 50 µL. Reduction in volume results in a potential annual reagent savings of almost $500,000 per year (see figure 5).
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| 50 µL Assay | 10 µL Assay | |
| Number of wells | 384 | 384 |
| Cost per well | $0.40 | $0.08 |
| Cost per plate | $154 | $31 |
| Number of plates per campaign | 200 | 201 |
| Cost per campaign | $30,720 | $6,175 |
| Number of campaigns per year | 20 | 20 |
| Annual reagent cost | $614,400 | $123,494 |
| Annual reagent savings realized by HTS lab* | $490,906 | |
Figure 5. HTS Reagent Cost Savings - 384-Well Format
* Reflects sample, not actual, costs incurred by the Chiron Corporation
Applications