In drug discovery, scientists prefer to explore potential therapeutics in their most natural forms. Label-free technology, which is actually a family of methods including nuclear magnetic resonance (NMR), surface plasmon resonance (SPR), and other approaches, offers one way to do that. When using label-free technology, scientists need to decide which label-free technology to consider instead of what to tag.
According to Ye Fang of Corning’s biochemical technologies: “Current drug discovery is dominated by label-dependent molecular approaches, which screen drugs in the context of a predefined and target-based hypothesis in vitro.” He added that “label-free cell phenotypic profiling with computational approaches [offers] a kinetic and holistic representation of the functional consequences of drugs in disease relevant cells that is amenable to mechanistic deconvolution.”
Analyzing with AIR
At Adarza BioSystems, AIR stands for arrayed imaging reflectometry. This technology can be used to detect antibodies, bacteria, nucleic acids, small proteins, and viruses. It can also cover a wide range of levels in the components being analyzed.
When asked about the main benefits of using label-free technology in drug discovery, Bryan Witherbee, president and CEO of Adarza BioSystems, says, “The main benefits of a label-free technology are versatility, flexibility, and simplicity in the design and execution of the assay.” He adds, “This is all related to the fact that we are measuring changes in reflectance—based on quantitative changes in mass—and not a label.”
Image: Adarza BioSystems’ arrayed imaging reflectometry can detect many analytes—antibodies to viruses and beyond—with no labeling required.
As an example of the flexibility of this technology, Witherbee says, “The arrays can be small or large.” He adds, “Label-free enables a customer to scale the biomarker continuum from single- to high-plex formats.” Plus, “a researcher can configure the array for the area of study and is not stuck with fixed content,” he explains.
Using this technology, though, requires some adjustments from researchers. “We are measuring mass and not fluorescence, so there is a newness and education process to better understand how the reflectance works and can be quantitative,” Witherbee explains. “Based on other label-free technologies, customers interpret label-free as measuring kinetics and real-time binding events.” The label-free technology from Adarza could do that, but Witherbee notes, “we wanted to launch a quantitative protein detection platform that offers the immunoassay world a better way to measure proteins.”
There is already evidence that this technology could enhance drug discovery. Adarza used its human and mouse cytokine arrays in a collaboration with an immuno-oncology drug development company and “helped them gain a more encompassing picture of the immune response to treatments in their humanized mouse tumor model,” Witherbee says. “Correlation of data generated by our technology compared to their ELISA results validated the use of our technology in their labs and switching to our multiplex, label-free technology will enable them to get more data for less time and money.”
Studies with SPR
To analyze molecular interactions on a surface, scientists can use SPR. With this technology, various platforms can be considered.
For example, Cytiva’s Biacore S200 can be used in low-molecular-weight and fragment-based drug discovery. The company states that this SPR platform “enables detailed characterization and optimization of lead compounds, even for difficult targets where response levels are low.” Plus, as many as 384 fragments can be screened in a day. With this platform, Cytiva adds that direct binding assays can be used to “identify site-selective binders directly using [a] competition assay.”
In addition, ForteBio, a Sartorius brand, offers its Pioneer and Pioneer FE Systems. The manufacturer describes these platforms as the “complete solution for biomolecular interaction analysis with next-generation SPR injections.” The company’s OneStep SPR injections provide many benefits, including the elimination of sample dilutions. Plus, these platforms can be used to collect kinetic data and affinity measurements to “characterize a wide range of biomolecular interactions from small molecule fragments to biologics,” the company writes.
Numbers from NMR
Label-free studies for new drugs can also use NMR. Like SPR, some NMR platforms come designed for drug discovery work.
One example is Bruker’s Fragment-Based Screening (FBS) solution. When combined with Mestrelab’s MScreen software, Bruker notes, this “provides drug discovery groups with an integrated experience from data acquisition and data analysis to the identification of hits in FBS-by-NMR campaigns.”
For fragment screening, Bruker states, “NMR is ideally suited for detecting these ligands, and screening by NMR allows the quality control of the screening library.”
Other options
Mass spectrometry can also be used as a label-free approach to drug discovery. As an example, scientists from Merck applied matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to peptides.
The Merck team reported: “It is essential to develop cutting-edge analytical techniques to support the discovery and development of peptide therapeutics, especially to examine their absorption, distribution, metabolism and excretion (ADME) properties.” These scientists used MALDI-MSI plus droplet-based liquid microjunction surface sampling liquid chromatography-high resolution mass spectrometry. From that, the scientists noted that they could “rapidly profile molecular information and provide structural insights on drug and metabolites.”
Conversely, some scientists create their own label-free system. That’s what a team of scientists in South Korea did. They used a normal-incidence type, solution-immersed silicon (NI-SIS) biosensor to detect cardiac troponin I, which can be an early indicator of a heart attack. Although the researchers used this technology as a biosensor in this example, they wrote that the “impressive biosensing capabilities of NI-SIS technology have huge potentials for accurate detection of target species in different application areas, such as diagnosis, drug discovery, and food contaminations.”
The collection of label-free technologies that scientists can consider in drug discovery studies offers many ways to search more effectively for tomorrow’s therapeutics. In most cases, off-the-shelf systems can cover a lab’s needs. To make the technology even better ahead, though, science and industry should support new approaches. Otherwise, biotechnology and pharmaceutical companies cannot reduce the current level of drug failures. Only with advanced techniques, like label-free platforms, can medical researchers improve treatments.