Surface Plasmon Resonance (SPR) is an optically based and label-free detection technique that can monitor the binding and dissociation processes of biomolecules by measuring plasmon resonance phenomena on metal surfaces. The throughput, flexibility, and sensitivity of the SPR technique make it applied to the study of biomolecular interactions in a wide range of fields.

The SPR instrument consists of an optical measurement system, a fluid handling system, and a sensor chip. The sensor chip is a glass substrate coated with a thin layer of gold, which is chemically modified to enable easier immobilization of one of the binding partners to the sensor surface. The sensor chip is connected to the fluidic system through the use of a small flow cell, allowing repeated injections of different concentrations of analytes in solution. The fluidic system provides a continuous flow of buffer through the flow cell and across the sensor chip, thus maintaining a well-controlled environment. Analytes can be easily injected into the flowing buffer to interact with the sensor surface for a specific period. The fluidic system is also used for ligand immobilization, analyte regeneration, cleaning, and conditioning. The optical system consists of a light source and a detector. The light source illuminates the gold film, and the detector measures the unique spectrum produced by the SPR phenomenon.

Once the ligand is immobilized on the sensor surface, the remaining binding sites are blocked. A solution containing an analyte then flows across the surface. The time it takes for the analyte to pass through the flow cell is called the conjugation phase, during which the analyte will accumulate on the surface as it binds to the ligand. The binding of the analyte to the ligand will result in an increase in signal until equilibrium is reached. Once the analyte passes through the flow cell and is replaced by the buffer, the analyte will begin to detach from the surface and the signal will begin to diminish. Molecular binding events or conformational changes along the surface interface result in measurable changes in the light absorbed by the detector and can be monitored over time.

SPR is becoming a standard technique available in many biochemistry laboratories because it adds value to research by revealing the true nature of binding interactions. SPR instruments can monitor molecular binding events label-free and in real-time, providing data on binding kinetics. In particular, SPR can be used for complex sample testing, such as testing crude samples in serum analysis. Moreover, the technique requires only a minimal amount of sample and allows for easy replication of experiments with reproducible sample injections, not only reducing the time required for expression and purification but also allowing reproducible measurements for accurate results. In addition, regeneration buffers are used to reverse analyte-ligand interactions, allowing the functionalized sensor surface to be used again.

SPR is unique because it is one of the few techniques that can measure binding kinetics, which provides real-time binding data during the association and dissociation phases of an interaction. For example, SPR can be used to measure binding between two proteins, such as proteins and antibodies, as well as DNA and proteins. This data provides a detailed understanding of the binding strength and stability of interactions, which is critical for many industries and research fields. Nowadays, SPR instruments are widely used for screening and development of new biotherapeutics drugs, quality control in bioprocess monitoring, development of new diagnostics, as well as basic research such as discovery and characterization of protein functions, and disease mechanisms.

Amerigo Scientific offers a wide range of SPR instruments and related accessories to determine which molecules interact, why they interact, and how strongly they interact.