A tool for running millions of biological or chemical tests in a short time is high-throughput screening. It is mainly used in drug discovery processes to identify biologically relevant compounds. Following you will learn what high throughput screening is, what is required to run high-throughput tests and which assays are primarily used.
High-throughput screening (HTS) is a drug discovery process that allows automated testing of large numbers of chemical and/or biological compounds for a specific biological target. High-throughput screening methods are extensively used in the pharmaceutical industry, leveraging robotics and automation to quickly test the biological or biochemical activity of a large number of molecules, usually drugs. They accelerate target analysis, as large scale compound libraries can quickly be screened in a cost effective way. HTS is a useful tool for assessing for instance pharmacological targets, pharmacologically profiling agonists and antagonists for receptors (such as GPCRs) and enzymes.
The primary goal of HTS is to identify through compound library screenings, candidates that affect the target in the desired way, so called hits or leads. This is usually achieved employing liquid handling devices, robotics, plate readers as detectors and dedicated software for instrumentation control and data processing.
Importantly, high-throughput screening processes do not usually identify drugs, as several properties that are critical to the development of a new drug cannot be assessed by compound library screening. For instance HTS cannot evaluate toxicity and bioavailability. The primary role of high-throughput screening assays is instead to identify leads and provide suggestions for their optimization. The results of HTS assays provide hence the starting point for further steps in the drug discovery pipeline like drug design, and for understanding the interaction or role of a particular biochemical process.
In recent times, HTS was largely enabled by the modern advances in robotics, liquid handling, plate reader detection as well as high-speed computers. Nevertheless, to run effectively, high-throughput screening still requires a highly specialized and expensive screening facility that not every lab can afford. As an alternative to setting up ones own facility, institutions with limited budgets usually access HTS services provided by third party provides such as Contract Research Organisations (CRO) or, mainly in an academic environment, core facilities.
Samples are usually of cellular or biochemical nature, depending on the assay to be run. High-throughput screening necessitates that samples are prepared in an arrayed format. The key platform or sample carrier used is therefore the microplate. Typical formats include 384-, 1536-, or 3456-well plates. The nature of the sample and of the detection assay may affect the choice of the microplate format and its colour. Screening facilities usually keep their compound library collections stored in so called stock plates. Stock plates are not directly used in experiments. Instead, when needed, compounds from a stock plate are copied to an assay plate through a pipetting station.
Automation is an important element in HTS as conversion of a benchtop to an automated high-throughput screening assay enforces specific constraints affecting the practical assay design. Ideally, a HTS assay is performed in a single well, with a low amount of reagents (miniaturization), and minimal or no further manipulation than injection of the sample/compound to be tested. Accordingly, the choice of the optimal detection mode and assay has to be subordinated to automation issues.For more information on the identification of false positives in screening attempts please see AN 359: Identification of false positives in a HTRF screen for small molecule inhibitors of PD-1/PD-L1.
Establishing a stringent assay and an effective quality control method are major issues when setting up an automated screen. The clearer the distinction between negative and positive controls, the higher the possibility to obtain high-quality data with a neglectable number of false negative but especially false positive results.
The scope of a robotic platform is to autonomously manage multiple plates simultaneously, significantly speeding up data acquisition. Robotic platforms for high-throughput screenings range from simple automated liquid handling machines to multidimensional workstations performing multiple functions. This is usually achieved with the support of one or more mechanical arms. Typically, a robotic system manages microplates from station to station for several steps such as reagent addition, mixing, incubation, and detection.
In high-throughput screenings data acquisition is usually performed by an optical measurement, quantifying the amount of light produced by the sample. Different readouts such as fluorescent or luminescent detection, colourimetry, or light scatter (turbidity) are available. Common detection modes include fluorescence intensity and polarization, FRET, time-resolved fluorescence (e.g.: HTRF, LANCE, etc), luminescence (e.g.: NanoBRET), and AlphaScreen.
Depending on the biological question to be answered, data quality as well as cost-effectiveness, different light-based detection readouts may be chosen. Specialized instrumentation, like multi-mode microplate readers, can sequentially perform different experiments or apply different detection protocols on the wells. The output thereof is a grid of numeric values.
To better understand what are the microplate reader requirements of screening facilities, read here Mark Wigglesworths full interview. Mark is Director of High-Throughput Screening at AstraZeneca in the UK and has integrated a PHERAstar FSX in AstraZeneca's screening facility.
We found that the improvements in the new PHERAstar FSX outperformed our historic experiences and the other readers in our trial. The reader has fitted well into our assay development and screening groups, where it has been used frequently for a variety of technologies.
A HTS-dedicated plate reader can measure hundreds of plates in a single day, generating a considerable amount of data points. Consequently, data management is a critical point in automated high-throughput screening, given the large number of compounds tested, the variety of chemical libraries and the necessity to correlate and compare results from different screening campaigns. Dedicated data analysis and management platforms (e.g.: Genedata) intertwine data originated from different screening campaigns with compound structures, as well as performed assays to each other, facilitating the extraction of detailed information from different perspectives.
Compound library screenings have to be usually measured as fast as possible, in very small volumes (a few L) and produce robust results. Besides the ease of use and flexibility to perform different assays, this requires a very sensitive and precise instrumentation. Watch Cline Legros from Servier, France, commenting on her experience with the PHERAstar platform.
Although one of the most targeted group of receptors in drug screening are G-Protein Coupled Receptors (GPCRs), not every benchtop assay can be converted to an automated HTS, especially when using living cells. Application Note 287 describes how for the first time NanoBRET was successfully used to monitor ligand-GPCRs binding in living cells.
An important issue in HTS is miniaturisation. Samples have to be as small as possible in order to save costs, but still deliver reliable results. The sensitivity of the microplate reader and its ability to reliably measure samples in high-density plate formats is consequently of great importance. In Application Note 229, DiscovereX PathHunter reporter cell lines were measured with the PHERAstar FS in both 1536- and 3456-well plates. The reader was able to detect signal coming from as few as 1,000 cells in a 1,536- and 250 cells in a 3,456-well plate. Similarly, Application Note 260 shows how an AlphaLISA assay was miniaturized down to 2 L per sample in a 1536-well plate and detected on the PHERAstar FS.
In drug screening, speed is as important as miniaturization. Application Note 295 shows how the PHERAstar FSX equipped with the TRF excitation laser, is able to detect HTRF assays in 1536-well plates on the fly in only 36 seconds, still delivering a Z` value > 0.8.
The Pivot Park Screening Centre in Oss, the Netherlands, relies on the PHERAstar FSX for effective hit discovery. In our customer success story Improving hit discovery efficiency at Europes leading screening centre, their CTO, Steven van Helden discusses innovation in drug discovery and the future of screening technology.
In the post Choosing the best microplate reader, Mark Wigglesworth, Director High Throughput Screening at AstraZeneca UK discusses the microplate reader requirements needed to keep up with AZs screening necessities and why AZ chose the PHERAstar FSX.
Searching for novel kinase inhibitors with the PHERAstar FSX plate reader at BIENTA laboratory in Kyiv, Ukraine. The HTS group screened more than 600,000 compounds in kinase assays using ATP depletion assay, measuring luminescence in a coupled luciferase reaction.
PHERAstar plate readers are routinely used in the laboratory as they provide an accurate signal, high throughput and sensitivity, as well as stable temperature control required for luminescent kinase assays.
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Gao, Q.; Zhang, C.; Liu, P.; Hu, Y.; Yang, K.; Yi, Z.; Liu, L.; Pan, X.; Zhang, Z.; Yang, J.; Chi, F. Effect of Back-Gate Voltage on the High-Frequency Performance of Dual-Gate MoS2 Transistors. Nanomaterials 2021, 11, 1594. https://doi.org/10.3390/nano11061594
Gao Q, Zhang C, Liu P, Hu Y, Yang K, Yi Z, Liu L, Pan X, Zhang Z, Yang J, Chi F. Effect of Back-Gate Voltage on the High-Frequency Performance of Dual-Gate MoS2 Transistors. Nanomaterials. 2021; 11(6):1594. https://doi.org/10.3390/nano11061594
Gao, Qingguo, Chongfu Zhang, Ping Liu, Yunfeng Hu, Kaiqiang Yang, Zichuan Yi, Liming Liu, Xinjian Pan, Zhi Zhang, Jianjun Yang, and Feng Chi. 2021. "Effect of Back-Gate Voltage on the High-Frequency Performance of Dual-Gate MoS2 Transistors" Nanomaterials 11, no. 6: 1594. https://doi.org/10.3390/nano11061594
Browse our large selection of new and used screening plants, not to be confused with static grizzly screens, for contractors in the road building, rock mining, aggregate producing, demolition, and recycling industries. Looking for trommel screens? Read MoreScreeners range from small and compact equipment to heavy-duty, high-output equipment including tracked mobile screening plants with scalping screens, grading screens, double deck and triple deck vibrating screens. Different deck bar spacing allows the separation of material into different sized products. Material to be separated and filtered includes topsoil, compost, rock, mulch, wood chips, sand, gravel, coal, loam, and more. Read Less
Widely used in fine wet screening applications, these high frequency screening machines comprise of up to five individual screen decks positioned one above the other operating in parallel. The stacked design allows for high-capacity units in a small footprint. The flow distributor splits the feed stream evenly to the individual polyurethane screen decks (openings down to 45 pm) where feeders distribute the stream across the entire width (up to 6 m) of each screen. Dual vibratory motors provide uniform linear motion to all screen decks. The undersize and oversize streams are individually combined and exit toward the bottom of the Stacked Sizer. Repulp sprays and trays arc an optional addition in between screen sections, which allow for increased screen efficiency.
By classifying by size-only, screens compared to hydrocyclones, give a sharper separation with multi-density feeds (for example, in PbZn operations), and reduce overgrinding of the dense minerals. Operations that replaced hydrocyclones with stackedhigh frequency screening machines in closing ball mill circuits can result in a decrease in the circulating load from 260% to 100% and 10 to 20% increase in circuit throughput.
The high capacity Stacked Sizing/screening machine consists of up to five decks positioned one above the other and all operating in parallel. Its use together with urethane screen surfaces as fine as 75 microns (200 mesh) has made fine wet screening a practical reality in mineral processing operations worldwide. The application of this technology in closed circuit grinding is demonstrated with specific application examples.
Screening is the process of separating particles by size and fine screening typically refers to separations in therange of 10 mm (3/8) to 38 microns (400 mesh). Fine screening, wet or dry, is normally accomplished with highfrequency, low amplitude, vibrating screening machines with either elliptical or straight-line motion. Various types ofwet and dry fine screening machines and the factors affecting their operation have been discussed previously.In fine particle wet screening, the undersize particles arc transported through the screen openings by the fluid andthe fraction of fluid in the slurry will therefore affect the efficiency of the separation. From a practical standpoint, the feed slurry to a fine screen should be around 20% solids by volume to achieve reasonable separation efficiency. Asmost of the fluid passes through the screen openings rather quickly, the fine screening process can be completed in ashort screen length. Therefore screen width, rather than screen area, is an important design consideration for fine wet screening.
Recognition of this concept led to the development of multiple feed point fine wet screening machines, or example, the Multifeed screen consists of three screen panels mounted within a rectangular vibrating frame and is actually three short screens operating in parallel. Each screen panel has its own feed box and the oversize from each panel flows into a common launder and then to the oversize chute. Similarly, the undersize from each of the three panels flows into the undersize hopper. The popular 1.2 m (4 ft) wide by 2.4 m (8 fl) long version has a total effective width of 3.0 m (10 fl) In general, multiple feed point machines have been shown to have 1.5 to 2 times more capacity than a single feed point machine of equivalent size and screen area.
Expanding further on this concept, the Stacked screening machine was introduced in 2001. With a capacity considerably greater than any other type of fine wet screening machine previously available, the Stack Sizer has up to five vibrating screen decks operating in parallel for a total effective width of 5.1 m (17 ft). The decks are positioned one above the other and each deck has its own feed box. A custom-engineered single or multiple-stage flow distribution system is normally included in the scope of supply to representatively split the feed slurry to each Stacked screen and then to the decks on each machine. Ample space is provided between each of the screen decks for clear observation during operation and easy access for maintenance and replacement of screen surfaces. Each screen deck, consisting of two screen panels in series, is equipped with an undersize collection pan which discharges into a common launder with a single outlet. Similarly, the oversize from each of the screen decks collects in a single hopper with a common outlet large vibrating motors rated at 1.9 kW (2 5 HP) each and rotating in opposite directions produce a uniform high frequency linear motion throughout the entire length and width of all screen decks for superior oversize conveyance.
As mentioned above, the fluid passing through the openings carries the undersize particles through the screen openings. The screening process is essentially complete when most of the fluid has passed through the openings. Any remaining undersize particles adhere to the coarse particles and are misdirected to the oversize product An optional repulping system is available for the Stack Sizer in which spray water is directed into a rubber-lined trough located between the two panels on each deck With this feature, oversize from the first panel is reslurried and screened again on the second panel. This repulping action maximizes the correct placement of undersize particles and its use will depend upon the particular objective of the screening machine.
To date, 1000s of screening machines are in operation at mineral processing plants worldwide. Dry mass flow capacity typically ranges from 100 to 350 t/h. This is roughly equivalent to 3 or 4 of the older style Multi-feed screens discussed above Like all screening machines, capacity depends upon many factors such as screen panel opening, weight recovery to oversize, the amount of near-size particles, particle shape, and slurry viscosity.
Sizers are for high capacity in a short compact machine. Generally you can make good cuts or separations with high efficiency. If you need near absolute 99.9% precision cuts, then a sizer cannot do that, and most inclined screeners also cannot. So that is why it is very important to understand what the separation goal is before selecting a screener. You cannot have high capacity and high accuracy + 99.9 in the same machine! This machine does not exist! A sizer generally can accomplish a similar separation of a single inclined screen in 2 or 3 screens, and 1/3 the length. of course a lot depends on the PSD, and how close the remaining particles are on each side of the desired cut.
TCI high frequency screens, commonly referred to as "PEP screens", come in a variety of sizes, frequency levels and configurations. Fine material is best separated with high speed and a small stroke. They are available in single or double deck configurations, and are equipped with either electric or hydraulic vibration. The ratchet-type screen tensioning makes for easy screen panel changes.
The high-frequency screens manufactured by Midwestern can be utilized in many screening applications from rugged quarry and rock sizing to sand and gravel processing and high volume fine mesh screening. With a variety of sizes and screening decks, the versatile MEV Screener can fit numerous applications.
The MEV High-Frequency Screener is a rectangular screener that utilizes an elliptical motion to convey material across itsscreening surface. Available in sizes three-foot by five-foot (3 x 5), four-foot by eight-foot (4 x 8), and five-foot by ten-foot (5 x 10) with the availability of one to five screening decks gives the MEV Screener the versatility to meet your screening needs.
The MEV Screener is designed to retain material at the feed end for a longer period of time and then gently slops the material near the discharge end, assisting itoff the screening deck and into production. This is achieved by the screeners unique parallel-arc configuration. Crossbars support the end-tensioned screens tocreate a flat screening surface, thus maximizing the screening area.
The end-tensioned screens used in the high-frequency screener simplify changing screen panels. End-tensioning permits the use of square-opening and slotted screens and is accurately maintained by a spring-loaded drawbar. Users can make screen changes in 1015 minutes.
Midwesterns commitment to providing our customers with outstanding screening products continues with our full line of replacement rectangular screens. Our screens are manufactured to fit all makes and models of screeners.Get in Touch with Mechanic