High-Throughput Screening
High-Throughput Screening
High-throughput screening (HTS) is an automated method for rapidly analyzing the activity of thousands of chemical compounds. It has become a key tool in modern drug discovery. Paired with combinatorial chemistry and bioinformatics , HTS allows potential drugs to be quickly and efficiently screened to find candidates that should be explored in more detail.
How the Process Works
Most drugs work by binding to a protein target on or in a living cell. One of the first steps in drug discovery and development is finding molecules that will bind to the target. Imagine, for instance, you want to develop an anticancer drug that binds to and inactivates a particular mutant protein known to promote aberrant cell growth. You have a couple of compounds that bind very weakly to your protein, and these serve as the starting point for generating a large number of related compounds, through combinatorial chemistry. In this method, many thousands of related compounds can be quickly and automatically synthesized. Those that bind best can be modified and tested further, and ultimately may go on to be tested in animals and people as candidate drug therapies.
Initial screening of these compounds for their binding ability is the job for HTS. The key to HTS is to develop a test, or assay, in which binding between a compound and a protein causes some visible change that can be automatically read by a sensor. Typically the change is emission of light by a fluorophore in the reaction mixture. One way to make this occur is to attach the fluorophore to the target protein in such a way that its ability to fluoresce is diminished (quenched) when the protein binds to another molecule. A different system measures the difference in a particular property of light (polarization) emitted by bound versus unbound fluorophores. Bound fluorophores are more highly polarized, and this can be detected by sensors. Other detection methods are possible as well.
The details of HTS differ with different systems, but all depend on automated or robotic systems to combine the chemicals and read the outputs. Reactions between the target protein and the compound usually occur in microplates, which are plastic trays with multiple indentations, or wells. Systems currently in use can handle plates with 96, 384, 1,536, or even higher numbers of wells at once. HTS typically uses extremely small volumes in each well, often 10 microliters or less. Small volumes have numerous advantages, including keeping to a minimum the amount of each compound used. This is especially important for many proteins targets, which may be difficult and costly to isolate and purify.
The time required for reactions varies with the substances involved, and may range from several minutes to several hours. Fast robotic systems combined with rapid reactions can screen 10,000 or more compounds in a single day. This is an enormous increase over traditional chemical assays, in which a chemist may be able to handle fewer than 100 tests in the same amount of time.
The Uses of HTS Assays
Storing, processing, analyzing, and accessing the wealth of data generated in an HTS assay poses special problems, simply because there is so much of it. Bioinformatics strategies are used to develop databases relating chemical structure, target characteristics, and assay results, allowing researchers to learn more from their results than just whether or not a particular compound was successful. Analyzing the common features of successful compounds may lead to rational development of better drug candidates.
High-throughput technology can also be put to use in other areas besides drug development. Indeed, any system in which there are many similar candidates to be screened, and in which a visible output can be designed, is amenable to high-throughput methods. Genomics applications are a principal area for applying HTS technology, in DNA sequencing, protein analysis, and other fields. HTS methods can be combined with DNA microarray technology, for instance, to analyze the expression of hundreds of different genes under varying conditions.
see also Bioinformatics; Biotechnology; Combinatorial Chemistry; DNA Microarrays; Proteomics.
Richard Robinson
Bibliography
Brush, Michael. "High-Throughput Technology Picks Up Steam." Scientist 13, no. 4 (February 15, 1999): 11.
Internet Resource
High Throughput Screening. <http://www.htscreening.net/>.