High throughput screening (HTS) is essential in the process of finding a potential drug candidate, and automation is key for a good screen both in terms of robustness and efficiency.
I kept hearing about the Echo since the day I joined Perlara, but it was only until a few weeks ago that I learnt how to use it. I knew that the Echo 550 from Labcyte Inc. was one of the most prized possessions of Perlara’s automation pipeline. I was truly amazed that it uses sound energy to transfer small amounts of our compounds from our source plates into our destination plates of choice. Since I am used to manual transfer, it was fascinating that we can transfer such small amounts with manual manipulation.
Being interested in learning a little more about how the Echo works, and inspire you to see if it is useful for your purposes, I wanted to write my first post on the ins and outs of the equipment. Here is a summary of the technology and how we use the Echo.
Labcyte Echo 550 acoustic liquid handling for high throughput screening of potential drug candidates.
Liquid handling is essential to HTS assays as the drug discovery experiment pipeline includes screening millions of compounds to identify as a potential drug candidate. The Acoustic Droplet Ejection (ADE) is a technology which uses highly focused sound energy to cause an ultra-small (2.5 nL) droplet to dislocate from a source well and deposit into a destination well (Fig 1) (Ellson, et al., 2003). To transfer a higher volume of liquid, multiple 2.5 nL droplets are transferred from the source well into the destination well. The Echo can transfer liquids from either 384 or 1536 well source plates to 96, 384, 1536 and 3456 well destination plates. We use 384 well LDV plates as our source plates and 384 well black walled glass bottom plates as destination plates in our cell experiment assays. However, we have turned into destination plate connoisseurs of all varieties for our various applications.
Figure 1. Transfer of 2.5 nL droplet from a source plate (A) well into a destination well using focused sound energy (B) from a transducer (C). Droplets can be transferred into dry empty as well as pre-filled destination wells.
The machine uses an ultrasound transducer to focus acoustic energy for initial surveying of each well in the source plate. This well survey calculates the depth of the liquid and amount of DMSO hydration, if your compounds are solubilized in DMSO. This is done by calculating the sound energy reflected by the plate bottom, well-bottom and meniscus of the liquid. This ensures the proper positioning of the transducer in order to accurately transfer the compound. The complete survey of a 384-well plate requires less than 26 seconds. The Echo can then transfer liquid into dry or pre-filled destination wells and can transfer liquid from any well of source plate into any well of the destination plate.
ADE is a very gentle technology and thus, can be used for transferring a variety of liquids including media containing cells (without causing a splash). Each liquid has a Weber number, and as long as it does not exceed 80, a splash does not occur during liquid transfer. The Weber number is based on the viscosity of the transferred drop of liquid, velocity, diameter and surface tension. Liquid droplets cause a splash when their Weber number is above 50 when transferring into a well that already has liquid in it, and in case of transferring into a dry well, a splash would occur only if the Weber number is above 80. Most of the common solvents including water and DMSO have a Weber number well below 50. (Ellson, et al., 2003)
Using the Echo 550 liquid handler software, one can create a protocol for the transfer of liquids/ compounds from a source plate into a destination plate. This protocol includes the volume of liquid to be transferred and the wells it is to be transferred from and to. Once this protocol is saved, it can be run using this button. Fig. 2 (Ellson, et al., 2003) illustrates how both the source and destination plates are loaded into the Echo. The software prompts you to load the source and destination plates. The Echo inverts the destination plate, so the inside of the destination wells is facing the material in the source plate, and then positions it directly above the source plate. The source plate is de-ionized as it is taken in to ensure straight travel of the liquid droplets. The surface tension keeps the liquid intact in the destination plate even though it is inverted. As you are loading the destination plate, a survey of the source plate is being conducted by the Echo which helps to determine whether all the wells have the required amount of liquid to be transferred. The maximum volume of liquid in each well of the 384-well LDV plate is 12.5 uL and the minimum volume is 2.5 uL. If the detected volumes are above or below the aforementioned limit, liquid will not be transferred onto the destination plate from these particular wells. A survey report is saved in a reports folder, which can be accessed in case we need to check liquid volumes or take note of any errors in liquid transfer.
Figure 2. Illustration depicting automation steps included in loading source and destination plates.
Some of the advantages of this technology include the ability to handle a variety of solvents, accuracy/ precision, and cost effectiveness. ADE can be used to transfer a range of solvents with viscosity ranging from 0.3 to 10 centipoise and with low coefficient of variation (CV). The technology is also capable of working with volatile liquids such as ethanol and acetone which have low viscosity and surface tension. Since transfer by ADE technology does not involve any physical contact, it minimizes the risk of contamination and/or cross-contamination.
One of the many applications of Echo is its use in the development of personalized medicine for cancer therapy. Commonly used chemotherapeutics might not work for every patient since each patient’s tumor is different based on the person’s acquired genetic mutation. The tumor might also gain resistance against common chemotherapeutics which is why personalized and targeted therapy is of the essence. The Echo helps in dispensing small amounts of all the compounds in a drug library to test each of them on patient samples. The destination plates which contain the patient samples along with the drugs are incubated for a certain period and then tested to see which drugs have managed to cause either a reversal in the tumor phenotype or kill the tumorous cells while not affecting the normal cells. This data along with other data related to the drug (dose curve, composition, etc.) can be provided to the doctor which would enable him/her to design a personalized treatment for the patient. (Labcyte, 2013)
We are going to start working on a couple of new diseases soon and I am looking forward to working with the Echo for our screens as well as dose response experiments. It is going to be exciting to learn more about the Echo and design experiments which would enable using our Echo 550 to its full potential!
References
Ellson, R., Mutz, M., Browning, B., Jr., L. L., Miller, M. F., & Papen, R. (2003). Transfer of Low Nanoliter Volumes between Microplates Using Focused Acoustics—Automation Considerations. Journal of the Association for Laboratory Automation 8(5), 29-34.
Labcyte. (n.d.). Personalized Medicine in Cancer: Applications: Echo 550. Retrieved from LABCYTE Web site: http://www.labcyte.com/applications/personalized-medicine
