Analyzing biomolecule interaction is vital for understanding biological processes and guiding drug development. Surface plasmon resonance (SPR) and bio-layer interferometry (BLI) are among the most widely available, label-free biosensor techniques to characterize biomolecule binding affinity and kinetics. But deciding which method to use requires careful consideration.

BLI is a fluidic-free technology that measures differences in the wavelength of reflected light caused by the binding of biomolecules between a layer of immobilized protein on a biosensor tip and a reference layer. The biosensor dips into samples and detects biomolecule interaction in real-time, providing compatibility with complex and crude samples. Another key advantage of BLI is throughput. The Sartorius Octet^® BLI platform is easily scalable and can analyze up to 96 binding reactions simultaneously. 

In contrast, SPR uses a sensor chip and detects changes in the refractive index from a light source when an analyte flows past a sensor in solution and interacts with an immobilized ligand on the sensor surface. Owing to its superior sensitivity and reproducibility, SPR is the gold standard for studying biomolecule binding. However, typical SPR experiments require multiple analyte titrations to accurately establish binding kinetics, limiting its utility in large screening assays. 

Sartorius’s Octet^® SF3 SPR circumvents the need for multiple dilutions through OneStep^® and NeXtStep™ Injections. SF3 SPR diffuses a single analyte concentration into a moving stream of buffer to create a concentration gradient and performs binding assays or competition assays, respectively. This novel approach offers a robust, high-throughput, low maintenance SPR solution for the rapid characterization of a wide variety of biomolecular and drug molecule interactions.