Biolayer interferometry (BLI) is a label-free technology for analyzing molecular interactions in real-time. This optical technique helps understand how biological molecules, such as proteins, nucleic acids, or viruses, interact. BLI provides insights into the binding events that underpin many biological processes.
What is Biolayer Interferometry
BLI measures changes in the thickness of a biological layer on a biosensor surface. The core principle involves light interference, where light reflects from two distinct surfaces: an internal reference layer within the biosensor and the outer surface where molecules bind. When molecules attach to or detach from the biosensor, the thickness of this outer biological layer changes. This causes a shift in the interference pattern of the reflected light.
The shifts in the interference pattern are precisely measured, providing real-time data on molecular binding. This allows researchers to track the association of molecules as they bind to the sensor surface and their dissociation as they release. BLI detects and measures these binding events by observing how the optical properties of the sensor surface change due to molecular interactions.
The Mechanism of Biolayer Interferometry
A BLI system comprises a light source, a detector, and biosensor tips. These biosensor tips are fiber-optic probes with a biologically active surface, often coated with compounds like streptavidin or protein A/G, which allow specific molecules to be immobilized. The instrument then dips these biosensor tips into solutions containing the molecules of interest.
A BLI experiment begins by establishing a baseline, where the biosensor is immersed in a buffer solution to determine a reference interference pattern. Next, a “ligand” molecule is immobilized onto the biosensor tip, and any unbound molecules are washed away. The biosensor is then moved into a solution containing the “analyte” molecule, designed to bind to the immobilized ligand.
As the analyte binds, it creates a new layer on the biosensor tip, changing the optical thickness and causing a measurable shift in the interference pattern. This shift is monitored in real-time, producing a binding curve that illustrates the association of the molecules. To study dissociation, the biosensor is moved back into a buffer, allowing the bound analyte to release from the ligand, and the resulting change in the interference pattern is again measured.
Real-World Applications of Biolayer Interferometry
BLI finds extensive use in drug discovery and development. It screens for new drug candidates by characterizing how potential drugs interact with their target molecules. This includes determining the strength of the binding (affinity) and the speed at which molecules bind and unbind (kinetics), which are both important for developing effective therapies.
The technology is also widely applied in antibody development. BLI helps in quantifying antibody concentrations, assessing their binding affinity to antigens, and guiding affinity maturation to improve their binding capabilities. BLI supports protein-protein interactions, which are fundamental to nearly all biological processes. It also aids vaccine development, identifying how vaccine components interact with targets to elicit an immune response.
Why Biolayer Interferometry is a Valuable Tool
BLI offers several advantages in research. Its label-free nature means it does not require molecules to be tagged with fluorescent markers or radioactive labels. This simplifies experiments and eliminates potential interference that labels might introduce, allowing for the study of unmodified biomolecules.
The technology provides real-time data acquisition, enabling scientists to observe molecular binding and dissociation as it happens. BLI can also analyze samples directly in crude or complex mixtures, such as cell culture supernatants or lysates, without extensive purification. Its high-throughput capabilities, allowing for simultaneous measurements on multiple biosensors, contribute to efficiency and accuracy in experiments.