Improving IC50 Results with Acoustic Droplet Ejection
Olechno J, Shieh J, Ellson R
Institution: Labcyte Inc.
Publication: Journal of Laboratory Automation August 2006 vol 11 no. 4 240-246, 10.1016/j.jala.2006.06.007
IC50 analyses are typically sample, time, and labor intensive. They commonly require multiple dilution steps and consume significant amounts of sample compound. Aqueous intermediate dilutions of concentrated stock solutions can lead to rapid sample precipitation and the generation of false negatives. Hydrophobic compounds may stick to pipette tips or intermediate dilution vessels, reducing the concentration of the analyte in the dilution and also increasing the possibility of cross contamination. The requirement for multiple serial dilutions in common IC50 analyses causes significant accumulated error. Concentrations of dimethyl sulfoxide (DMSO), the typical solvent used to solubilize compound libraries, as low as 1% in the final assay solution can significantly affect the results of the experiment. Finally, the cost of pipette tips and intermediate dilution vessels, and the frequency of the DMSO washes of tips grows significantly as the number of compounds being analyzed is increased. A system incorporating acoustic droplet ejection of compounds improves IC50 results by reducing the amount of sample used in the analysis to nanoliters, eliminating intermediate aqueous dilutions and accumulated pipetting error, lowering DMSO concentrations in the final assay to below 1%, and reducing costs of consumables (plastics, solvents, and their disposal).
Publication / Type:Journal of Laboratory Automation August 2006 vol 11 no. 4 240-246, 10.1016/j.jala.2006.06.007
Related Subject:ADE, DMSO impact on assays, aqueous intermediate dilutions, dose-response, Echo, dose-response, IC50, cost reduction, throughput, cross-contamination
Compounds used in high throughput screening (HTS) are typically dissolved in DMSO. These solutions are stored automation-friendly racks of wells or tubes. DMSO is hygroscopic and quickly absorbs water from the atmosphere. When present in DMSO compound solutions, water can accelerate degradation and precipitation. Understanding DMSO hydration in an HTS compound library can improve storage and screening methods by managing the impact of water on compound stability. A non-destructive, acoustic method compatible with HTS has been developed to measure water content in DMSO solutions. Performance of this acoustic method was compared with an optical technique and found to be in good agreement. The accuracy and precision of acoustic measurements was shown to be under 3% over the tested range of DMSO solutions (0% to 35% water by volume) and insensitive to the presence of HTS compounds at typical storage concentrations. Time course studies of hydration for wells in 384-well and 1536-well microplates were performed. Well geometry, fluid volume, well position and atmospheric conditions were all factors in hydration rate. High rates of hydration were seen in lower-volume fills, higher-density multi-well plates and when there was a large differential between the humidity of the lab and the water content of the DMSO. For example, a 1536-well microplate filled with 2μL of 100% DMSO exposed for one hour to a laboratory environment with ∼40% relative humidity will absorb over 6% water by volume. Understanding DMSO hydration rates as well as the ability to reverse library hydration are important steps towards managing stability and availability of compound libraries.
Transfer of low nanoliter volumes between microplates using focused acoustics—automation considerations
Ellson R, Mutz M, Browning B, Lee L, Miller M and Papen R
Institution: Labcyte Inc.and BMG Labtech
Publication: Journal of the Association for Laboratory Automation (Impact Factor: 1.5). 01/2003; 8(5):29-34. DOI:
Acoustic droplet ejection (ADE) gently and precisely aliquots nanoliter and picoliter liquid volumes without any physical contact with the solution being transferred. The technology is very automation-friendly, as it is compatible with conventional microplates. Focused energy from an acoustic transducer induces droplet ejection into an inverted standard microplate. The commercial system transfers low-nanoliter volumes of dimethyl sulfoxide–dissolved compound libraries and thereby enables cell-based assays to be performed in 1536-well plates.
Publication / Type:Journal of the Association for Laboratory Automation (Impact Factor: 1.5). 01/2003; 8(5):29-34. DOI:
Related Subject:nanoliter microplates focused acoustics automation