Bruker's surface plasmon resonance solution

Unlocking the Analytical Power of Surface Plasmon Resonance

Surface plasmon resonance (SPR) is an optical-based, label-free detection technology for real-time monitoring of binding interactions between two or more molecules.  A wide range of molecules can be studied, from ions and fragments to proteins and viruses. This innovative technology is capable of providing biophysical data such as affinity, kinetics and thermodynamics, in addition to answering basic questions of binding specificity and concentration.

SPR-based analytical biosensors can be extremely powerful tools for the characterization of molecular interactions. The combination of three individual elements, the detector, the sensor surface and the sample delivery system are critical to the performance of the experiment.

SPR: Real-time, Label-free Optical Detection

Optical-based detection using SPR
Optical-based detection using SPR (click to enlarge)

Binding interactions between a molecule on the sensor surface (ligand) and its binding partner(s) in solution (analyte) are monitored in real-time by SPR. SPR uses a type of total internal reflection and causes a reduction in the light intensity reflected at a specific angle from the glass side of the sensor surface.  As molecules bind, the refractive index close to the surface changes causing a shift in the angle of minimum reflected intenstiy. The change in angle is proportional to the mass of bound material. The typical output is a sensorgram, which monitors the change in angle as a function of time.

Molecules Interact at the Sensor Surface

User-friendly sensors reduce assay variability
User-friendly sensors reduce assay variability

The sensors used in the Sierra SPR systems are gold-plated prisms mounted on easy-to-handle cartridges. The design makes installation straightforward and eliminates user-related assay variablilty. The gold surface, which is required for SPR, is coated with a self-assembled monolayer to block nonspecific binding of proteins and to facilitate the attachment of molecules to the surface. The increasing variety of surface linkage chemistries broadens the utility of analytical biosensors for a wide range of applications.

Novel Continuous Flow Microfluidics

Sample delivery to the sensor surface via a continuous flow microfluidic device yields the most accurate binding measurements. For reproducible sample delivery, the Sierra SPR-32 system utilizes proprietary Hydrodynamic Isolation™ (HI) technology. HI is a method for presenting small, yet highly discrete fluid volumes, to isolated locations on a two-dimensional surface contained within a flow cell under laminar flow. Location-specific fluid addressing within the flow cell is facilitated by combining components of hydrodynamic focusing with site-specific evacuation. The process does not require the use of physical barriers within the flow cell or mechanical valves to control the paths of fluid movement, thereby permitting high-throughput multiplexing or the construction of two-dimensional arrays with individually addressable detection spots.