Not your Jedi’s ‘LIGHTSABR’

Scripps Florida researchers develop a cheap, portable drug discovery system

Jeffrey Bouley
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JUPITER, Fla.—With the popularity of “Star Wars”—or at least its ubiquitousness—hardly ever having flagged since the 1970s, it would be hard to find (at least in America) too many people who don’t know what the fictional lightsaber or a Jedi knight is.
Well, now researchers may, in reality, be imaging battles against the “Dark Side” of disease with a new system dubbed LIGHTSABR (light-induced and graduated high-throughput screening after bead release) for its light-based cleavage of compounds from their carrier beads.
The idea, coming from scientists at the Florida campus of The Scripps Research Institute (TSRI), was to make the screening of large libraries of compounds orders of magnitude smaller and cheaper—freeing researchers somewhat from large, expensive and dedicated facilities.
“We’ve developed a device that can do the functional equivalent of high-throughput compound screening on an ultra-miniaturized scale,” said the study’s principal investigator Brian M. Paegel, an associate professor at TSRI.
The device, according to TSRI, “overcomes significant technical hurdles concerning the smooth flow of droplets, the absorption of stray UV irradiation and calibration of the UV waveguide.”
One key innovation is that the LIGHTSABR technique makes it possible for users to vary the UV illumination to adjust the amount of a compound cleaved from its bead, and thus adjust the dose of the compound being tested. Pagel’s team successfully demonstrated this dosing function using an assay designed to find inhibitors of HIV-1 protease, a key enzyme involved in the replication of the virus that causes AIDS.
These advances come on the heels of a previous study from Paegel’s laboratory that described the synthesis of miniaturized DNA-encoded compound libraries. The new screening device is designed to work with the new type of library.
The new approach starts with the use of “one-bead-one-compound” (OBOC) libraries, in which individual compounds are chemically attached to microscopic beads. TSRI notes that the past couple decades have seen more and more laboratories shift to working with OBOC libraries, which are so compact and can be so quickly and inexpensively prepared that they could almost be categorized along with laboratory consumables.
“It is possible to generate an OBOC library of millions of compounds in a week for about $500,” according to Alexander K. Price, a senior research associate in the Paegel laboratory.
To overcome the technical challenges of putting bead-borne compounds through miniature screening devices, Paegel and Price engineered a benchtop-scale device using much the same microfluidics principles associated with inkjet printer technology.
In the end, the LIGHTSABR device introduces OBOC library beads into tiny liquid droplets that contain the assay of interest, such as an enzymatic activity assay. The volume of these assay droplets is about 100,000 times less than the volumes used for high-throughput screening assays. The device then frees each compound from its bead with a photochemical reaction induced by ultraviolet (UV) light and, after an appropriate period of incubation, records the result in each droplet.
The next step, say Paegel and Price, is to apply the microfluidic LIGHTSABR and the laboratory’s DNA-encoded OBOC libraries. “In addition to antiviral compounds, we are also pursuing new antibiotics and other drug classes that address the emergence of resistance in rapidly evolving pathogens,” said Paegel. “Hundreds of laboratories around the world could operate their own miniaturized screening facilities, using their own assays to go after targets that are of most interest to them.”

Jeffrey Bouley

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