BLI vs SPR: Picking the Right Tool for Discovery Campaigns in Biotechs
At Immune Biosolutions, we leverage two core technologies, Bio-Layer Interferometry (BLI) and High-Throughput Surface Plasmon Resonance (HT-SPR), for antibody discovery. Below is a brief overview of their unique and synergistic value as part of our discovery workflows.
Bio-Layer Interferometry (BLI) and Surface Plasmon Resonance (SPR) have become indispensable tools for the high-throughput characterization of protein–protein interactions. They enable researchers to study, in real time, how molecules engage—such as an antibody recognizing its antigen or two recombinant proteins forming a complex. Both technologies rely on detecting minute changes in refracted light at the sensor interface to capture binding events without the need for labels. Despite this shared principle, they differ in important ways that influence their applications and performance. Before diving into practical examples, it is worth outlining the theoretical basis of each technique.
Surface Plasmon Resonance (SPR)
Surface Plasmon Resonance (SPR) is an optical technique that measures molecular interactions in real time without the need for labels. It relies on a thin metal film—typically gold—that supports surface plasmons (electron oscillations) sensitive to changes in the local refractive index. One binding partner (the ligand) is immobilized on the gold surface, while the other (the analyte) is flowed across in solution. When binding occurs, the refractive index at the surface changes, producing a measurable shift in the resonance signal. This shift is monitored continuously, providing detailed kinetic information on association and dissociation.
Biolayer Interferometry (BLI)
Bio-Layer Interferometry (BLI) is an optical technique that monitors biomolecular interactions using disposable biosensor tips. One binding partner, for example, an antibody, is immobilized on the sensor surface, and the tip is then dipped into wells containing the analyte. Binding events alter the interference pattern of reflected light, allowing real-time measurement of association and dissociation
At Immune Biosolutions, we operate both a Carterra LSA (HT-SPR) and a Sartorius Octet RED384, each optimized for specific applications. Typically, for our experiment designs, the Carterra LSA offers higher throughput with better technical replicability than the Octet RED384. This stems from the fact that antibodies are bound to the chip and are exposed to the same ligand solution across all positions. BLI is typically better for very large or very small molecules. Here are a few examples of particular use cases with each instrument’s strengths and limitations.
Rapid Screening of scFvs from Crude Extracts
In our laboratory, either instrument have optimized procedures to generate high quality data, that slightly differ.
SPR
The continuous flow system of SPR produces higher-resolution kinetic curves, especially important when accurate rate constants are needed. The best precision is obtained when using purified samples. Therefore, in practice, crude extracts are ideal for rapid pre-screening, with promising candidates later purified and re-analyzed for more detailed kinetic characterization.
BLI
The dip-and-read format of BLI makes it well suited for unpurified samples, since there are no microfluidics that might clog. This enables straightforward screening directly from bacterial supernatants. For lower throughput, or for very small or very large molecules, BLI may be well suited.
Testing Small Molecules binding
Small molecules generate only subtle refractive index changes, so sensitivity is critical.
SPR
The Carterra LSA instrument is less suitable for small molecules. The experimental plan should be discussed specifically according to the client’s molecule type and size. When appropriate, the continuous flow design and high optical sensitivity make it well suited for detecting weak, transient signals.
BLI
Small molecules are assessed using our BLI platform, for which we have optimized protocols to accurately capture data at these sizes. BLI enables the detection of weak signals that are characteristic of these assays. The experimental design will be discussed in detail according to the specific size and nature of the molecule of interest.
Screening for Binders to a Large Protein Complex
When working with very large protein assemblies, assay format and surface tolerance become critical. Large complexes can present challenges for fluidics-based systems, both in terms of stability and potential clogging.
SPR
While SPR instruments can measure interactions with large complexes, the flow-based design of our Carterra LSA can complicate experiments with such bulky analytes. For this reason, depending on the size, BLI may be more appropriate.
BLI
The dip-and-read format of BLI makes it especially forgiving for large molecular species. Because there are no microfluidics, issues like clogging or shear stress on the complex are avoided. This makes BLI the preferred platform for screening binders against large protein complexes, where robustness and assay simplicity are more important than ultra-fine kinetic resolution.
Epitope Binning
Epitope binning is essential for grouping antibodies that recognize overlapping or distinct regions on the same antigen.
SPR
High-resolution binning can be performed on SPR, often with greater sensitivity and higher-resolution kinetics curves. It provides a more detailed picture of binding overlaps and competition.
BLI
BLI is well suited for parallel binning experiments with very large molecules. In our setup, we can run up to 16 binning assays simultaneously, which makes it efficient for clustering large antibodies. The trade-off is that the resolution is somewhat lower compared to SPR, meaning closely overlapping epitopes may not be fully distinguished.
In conclusion, both BLI and SPR offer powerful, complementary attributes to advance molecular discovery. Combined, these technologies empower researchers to explore biomolecular interactions from early screening to high-resolution characterization. It ensures a comprehensive, efficient, and reliable approach to accelerate biologics discovery.
For more details on antibody and biomanufacturing services available at Immune Biosolutions, visit our website or contact our team directly for more details.
About Immune Biosolutions
Immune Biosolutions is a clinical-stage biotechnology company specializing in the discovery and engineering of avian and human antibodies for therapeutic applications. Utilizing cutting-edge technologies, we develop custom immunotherapeutic agents. Our discovery platform efficiently targets complex proteins and generate powerful, specific, and innovative antibodies. Additionally, our antibody production capability allows us to advance our own discovery programs in cancer and autoimmune diseases into the early phases of clinical development.
